Network Working Group F. Strauss
Internet-Draft J. Schoenwaelder
Expires: January 18, 2002 TU Braunschweig
July 20, 2001
SMIng - Next Generation Structure of Management Information
draft-ietf-sming-02
Status of this Memo
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all provisions of Section 10 of RFC2026.
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Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
This memo presents an object-oriented data definition language for
the specification of various kinds of management information. It is
independent of management protocols and applications. Protocol
mappings are defined as extensions to this language in separate
memos. The language builds on experiences gained with the SMIv2 and
its derivate SPPI. It is expected that the language presented in
this memo along with its protocol mappings will replace the SMIv2 and
the SPPI in the long term.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. SMIng Data Modelling . . . . . . . . . . . . . . . . . . . . 5
2.1 Identifiers . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Base Types and Derived Types . . . . . . . . . . . . . . . . 7
3.1 OctetString . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3 Object Identifier . . . . . . . . . . . . . . . . . . . . . 9
3.4 Integer32 . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.5 Integer64 . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.6 Unsigned32 . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.7 Unsigned64 . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.8 Float32 . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.9 Float64 . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.10 Float128 . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.11 Enumeration . . . . . . . . . . . . . . . . . . . . . . . . 16
3.12 Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.13 Display Formats . . . . . . . . . . . . . . . . . . . . . . 18
4. The SMIng File Structure . . . . . . . . . . . . . . . . . . 20
4.1 Comments . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.2 Statements and Arguments . . . . . . . . . . . . . . . . . . 20
5. The module Statement . . . . . . . . . . . . . . . . . . . . 20
5.1 The module's import Statement . . . . . . . . . . . . . . . 21
5.2 The module's organization Statement . . . . . . . . . . . . 22
5.3 The module's contact Statement . . . . . . . . . . . . . . . 22
5.4 The module's description Statement . . . . . . . . . . . . . 22
5.5 The module's reference Statement . . . . . . . . . . . . . . 22
5.6 The module's revision Statement . . . . . . . . . . . . . . 22
5.6.1 The revision's date Statement . . . . . . . . . . . . . . . 22
5.6.2 The revision's description Statement . . . . . . . . . . . . 23
5.7 Usage Example . . . . . . . . . . . . . . . . . . . . . . . 23
6. The extension Statement . . . . . . . . . . . . . . . . . . 24
6.1 The extension's status Statement . . . . . . . . . . . . . . 24
6.2 The extension's description Statement . . . . . . . . . . . 24
6.3 The extension's reference Statement . . . . . . . . . . . . 24
6.4 The extension's abnf Statement . . . . . . . . . . . . . . . 25
6.5 Usage Example . . . . . . . . . . . . . . . . . . . . . . . 25
7. The typedef Statement . . . . . . . . . . . . . . . . . . . 25
7.1 The typedef's type Statement . . . . . . . . . . . . . . . . 25
7.2 The typedef's default Statement . . . . . . . . . . . . . . 26
7.3 The typedef's format Statement . . . . . . . . . . . . . . . 26
7.4 The typedef's units Statement . . . . . . . . . . . . . . . 26
7.5 The typedef's status Statement . . . . . . . . . . . . . . . 27
7.6 The typedef's description Statement . . . . . . . . . . . . 27
7.7 The typedef's reference Statement . . . . . . . . . . . . . 27
7.8 Usage Examples . . . . . . . . . . . . . . . . . . . . . . . 27
8. The identity Statement . . . . . . . . . . . . . . . . . . . 28
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8.1 The identity's status Statement . . . . . . . . . . . . . . 29
8.2 The identity' description Statement . . . . . . . . . . . . 29
8.3 The identity's reference Statement . . . . . . . . . . . . . 29
8.4 Usage Examples . . . . . . . . . . . . . . . . . . . . . . . 30
9. The class Statement . . . . . . . . . . . . . . . . . . . . 30
9.1 The class' attribute Statement . . . . . . . . . . . . . . . 30
9.1.1 The attribute's access Statement . . . . . . . . . . . . . . 31
9.1.2 The attribute's default Statement . . . . . . . . . . . . . 31
9.1.3 The attribute's format Statement . . . . . . . . . . . . . . 31
9.1.4 The attribute's units Statement . . . . . . . . . . . . . . 32
9.1.5 The attribute's status Statement . . . . . . . . . . . . . . 32
9.1.6 The attribute's description Statement . . . . . . . . . . . 32
9.1.7 The attribute's reference Statement . . . . . . . . . . . . 33
9.2 The class' unique Statement . . . . . . . . . . . . . . . . 33
9.3 The class' event Statement . . . . . . . . . . . . . . . . . 33
9.3.1 The event's status Statement . . . . . . . . . . . . . . . . 33
9.3.2 The event's description Statement . . . . . . . . . . . . . 34
9.3.3 The event's reference Statement . . . . . . . . . . . . . . 34
9.4 The class' status Statement . . . . . . . . . . . . . . . . 34
9.5 The class' description Statement . . . . . . . . . . . . . . 34
9.6 The class's reference Statement . . . . . . . . . . . . . . 35
9.7 Usage Example . . . . . . . . . . . . . . . . . . . . . . . 35
10. Extending a Module . . . . . . . . . . . . . . . . . . . . . 36
11. SMIng Language Extensibility . . . . . . . . . . . . . . . . 37
12. Security Considerations . . . . . . . . . . . . . . . . . . 39
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 39
References . . . . . . . . . . . . . . . . . . . . . . . . . 40
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 41
A. SMIng ABNF Grammar . . . . . . . . . . . . . . . . . . . . . 41
B. OPEN ISSUES . . . . . . . . . . . . . . . . . . . . . . . . 51
Full Copyright Statement . . . . . . . . . . . . . . . . . . 54
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1. Introduction
In traditional management systems management information is viewed as
a collection of managed objects, residing in a virtual information
store, termed the Management Information Base (MIB). Collections of
related objects are defined in MIB modules. These modules are
written conforming to a specification language, the Structure of
Management Information (SMI). There are different versions of the
SMI. The SMI version 1 (SMIv1) is defined in [9], [10], [11] and the
SMI version 2 (SMIv2) in [5], [6], [7]. Both are based on adapted
subsets of OSI's Abstract Syntax Notation One, ASN.1 [13].
In a similar fashion policy provisioning information is viewed as a
collection of Provisioning Classes (PRCs) and Provisioning Instances
(PRIs) residing in a virtual information store, termed the Policy
Information Base (PIB). Collections of related Provisioning Classes
are defined in PIB modules. PIB modules are written using the
Structure of Policy Provisioning Information (SPPI) [8] which is an
adapted subset of SMIv2.
The SMIv1 and the SMIv2 are bound to the Simple Network Management
Protocol (SNMP) while the the SPPI is bound to the Common Open Policy
Service Provisioning (COPS-PR) protocol. Even though the languages
have common rules, it is hard to use common data definitions with
both protocols. It is the purpose of this document to define a
common object-oriented data definition language, named SMIng, that
allows to formally specify data models independent of specific
protocols and applications. Companion documents contain
o core modules that supply common SMIng definitions [1][2],
o a SMIng language extension to define SNMP specific mappings of
SMIng definitions in way compatible to SMIv2 MIBs [3], and
o a SMIng language extension to define COPS-PR specific mappings of
SMIng definition in a way compatible to SPPI PIBs.
Section 2 gives an overview of the basic concepts of data modelling
using SMIng while the subsequent sections present the concepts of the
SMIng language in detail: the base types, the SMIng file structure,
and all SMIng core statements.
The remainder of the document describes extensibility features of the
language and rules to follow when changes are applied to a module.
Appendix A contains the grammar of SMIng in ABNF [12] notation.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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document are to be interpreted as described in [4].
2. SMIng Data Modelling
SMIng is a language designed to specify management information in a
structured way readable to computer programs, e.g. MIB compilers, as
well as to human readers.
Management information is modeled in classes in an object-oriented
manner. Classes can be defined from scratch or by inheritance from a
parent class. Multiple inheritence is not possible. The concept of
classes is described in Section 9.
Each class has a number of attributes. Each attribute represents an
atomic piece of information of a base type, a sub-type of a base
type, or another class. The concept of attributes is described in
Section 9.1.
The base types of SMIng include signed and unsigned integers, octet
strings, enumeration types, bitset types, and pointers. Pointers are
references to class instances, attributes of class instances, or
arbitrary identities. The SMIng type system is described in Section
3.
Related class and type definitions are defined in modules. A module
may refer to definitions from other modules by importing identifiers
from those modules. Each module may serve one or multiple purposes:
o the definition of management classes,
o the definition of events,
o the definition of derived types,
o the definition of arbitrary untyped identities serving as values
of pointers,
o the definition of SMIng extensions to allow the local module or
other modules to specify information beyond the scope of the base
SMIng in a machine readable notation. Some extensions for the
application of SMIng in the SNMP framework are defined in [3],
o the definition of information beyond the scope of the base SMIng
statements, based on locally defined or imported SMIng extensions.
Each module is identified by an upper-case identifier. The names of
all standard modules must be unique (but different versions of the
same module should have the same name). Developers of enterprise
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modules are encouraged to choose names for their modules that will
have a low probability of colliding with standard or other enterprise
modules, e.g. by using the enterprise or organization name as a
prefix.
2.1 Identifiers
Identifiers are used to identify different kinds of SMIng items by
name. Each identifier is valid in a namespace which depends on the
type of the SMIng item being defined:
o The global namespace contains all module identifiers.
o Each module defines a new namespace. A module's namespace may
contain definitions of extension identifiers, derived type
identifiers, identity identifiers, and class identifiers.
Furthermore, a module may import identifiers of these kinds from
other modules. All these identifiers are also visible within all
inner namespaces of the module.
o Each class within a module defines a new namespace. A class'
namespace may contain definitions of attribute identifiers and
event identifiers.
o Each enumeration type and bitset type defines a new namespace of
its named numbers. These named numbers are visible in each
expression of a corresponding value, e.g., default values and sub-
typing restrictions.
o Extensions may define additional namespaces and have additional
rules of other namespaces' visibilty.
Within every namespace each identifier MUST be unique.
Each identifier starts with an upper-case or lower-case character,
dependent on the kind of SMIng item, followed by zero or more
letters, digits and hyphens.
All identifiers defined in a namespace MUST be unique and SHOULD NOT
only differ in case. Identifiers MUST NOT exceed 64 characters in
length. Furthermore, the set of all identifiers defined in all
modules of a single standardization body or organization SHOULD be
unique and mnemonic. This promotes a common language for humans to
use when discussing a module.
To reference an item that is defined in the local module, its
definition MUST sequentially precede the reference. Thus, there MUST
NOT be any forward references.
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To reference an item, that is defined in an external module it MUST
be imported into the local module's namespace (Section 5.1).
Identifiers that are neither defined nor imported MUST NOT be visible
in the local module. On the other hand, all items defined in a
module are implicitly exported.
When identifiers from external modules are referenced, there is the
possibility of name collisions. As such, if different items with the
same identifier are imported or if imported identifiers collide with
identifiers of locally defined items, then this ambiguity is resolved
by prefixing those identifiers with the names of their modules and
the namespace operator `::', i.e. `Module::item'. Of course, this
notation can be used to refer to identifiers even when there is no
name collision.
Note that SMIng core language keywords MUST NOT be imported. See the
`...Keyword' rules of the SMIng ABNF grammar in Appendix A for a list
of those keywords.
3. Base Types and Derived Types
SMIng has a minimal but complete set of base types, similar to those
of many programming languages, but with some differences due to
special requirements from the management information model.
Additional types may be defined, derived from those base types or
from other derived types. Derived types may use subtyping to
formally restrict the set of possible values. An initial set of
commonly used derived types is defined in the SMIng standard module
IETF-SMING [1].
The different base types and their derived types allow different
kinds of subtyping, namely size restrictions and range restrictions.
See the following sections on base types (Section 3.1 through Section
3.12) for details.
3.1 OctetString
The OctetString base type represents arbitrary binary or textual
data. Although SMIng has a theoretical size limitation of 2^16-1
(65535) octets for this base type, module designers should realize
that there may be implementation and interoperability limitations for
sizes in excess of 255 octets.
Values of octet strings may be denoted as textual data enclosed in
double quotes or as arbitrary binary data denoted as a `0x'-prefixed
hexadecimal value of an even number of at least two hexadecimal
digits, where each pair of hexadecimal digits represents a single
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octet. Letters in hexadecimal values MAY be upper-case but lower-
case characters are RECOMMENDED. Textual data may contain any number
(possibly zero) of any 7-bit displayable ASCII characters except
double quote `"', including tab characters, spaces and line
terminator characters (nl or cr & nl). Textual data may span
multiple lines, where each subsequent line prefix containing only
white space up to the column where the first line's data starts
SHOULD be skipped by parsers for a better text formatting.
When defining a type derived (directly or indirectly) from the
OctetString base type, the size in octets may be restricted by
appending a list of size ranges or explicit size values, separated by
pipe `|' characters and the whole list enclosed in parenthesis. A
size range consists of a lower bound, two consecutive dots `..' and
an upper bound. Each value can be given in decimal or `0x'-prefixed
hexadecimal notation. Hexadecimal numbers must have an even number
of at least two digits. Size restricting values MUST NOT be
negative. If multiple values or ranges are given, they all MUST be
disjoint and MUST be in ascending order. If a size restriction is
applied to an already size restricted octet string the new
restriction MUST be equal or more limiting, that is raising the lower
bounds, reducing the upper bounds, removing explicit size values or
ranges, or splitting ranges into multiple ranges with intermediate
gaps.
Value Examples:
"This is a multiline
textual data example." // legal
"This is "illegally" quoted." // illegal quotes
"But this is 'ok'." // legal apostrophe quoting
"" // legal zero length
0x123 // illegal odd hex length
0x534d496e670a // legal octet string
Restriction Examples:
OctetString (0 | 4..255) // legal size spec
OctetString (4) // legal exact size
OctetString (-1 | 1) // illegal negative size
OctetString (5 | 0) // illegal ordering
OctetString (1 | 1..10) // illegal overlapping
3.2 Pointer
The Pointer base type represents values that reference class
instances, attributes of class instances, or arbitrary identities.
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The only values of the Pointer type that can be present in a module
can refer to identities. They are denoted as identifiers of the
concerned identities.
When defining a type derived (directly or indirectly) from the
Pointer base type, the values may be restricted to a specific class,
attribute or identity and all (directly or indirectly) derived items
thereof by appending the identifier of the appropriate construct
enclosed in parenthesis.
Value Examples:
null // legal identity name
snmpUDPDomain // legal identity name
Restriction Examples:
Pointer (snmpTransportDomain) // legal restriction
3.3 Object Identifier
The ObjectIdentifier base type represents administratively assigned
names for use with SNMP and COPS-PR. This type SHOULD NOT be used in
protocol independant SMIng modules. It is meant to be used in SNMP
and COPS-PR mappings of attributes of type Pointer (Section 3.2).
Values of this type may be denoted as a sequence of numerical non-
negative sub-identifier values which each MUST NOT exceed 2^32-1
(4294967295). Sub-identifiers may be denoted decimal or `0x'-
prefixed hexadecimal. They are separated by single dots and without
any intermediate white space. Alternatively (and preferred in most
cases), the first element may be a previously defined or imported
lower-case identifier, representing a static object identifier
prefix. The total number of sub-identifiers MUST NOT exceed 128
including the expanded identifier.
Object identifier derived types cannot be restricted in any way.
Value Examples:
1.3.6.1 // legal numerical oid
mib-2.1 // legal oid with identifier prefix
internet.4.1.0x0627.0x01 // legal oid with hex subids
iso.-1 // illegal negative subid
iso.org.6 // illegal non-heading identifier
IF-MIB::ifNumber.0 // legel fully quallified instance oid
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3.4 Integer32
The Integer32 base type represents integer values between -2^31 (-
2147483648) and 2^31-1 (2147483647).
Values of type Integer32 may be denoted as decimal or hexadecimal
numbers, where only decimal numbers can be negative. Decimal numbers
other than zero MUST NOT have leading zero digits. Hexadecimal
numbers are prefixed by `0x' and MUST have an even number of at least
two hexadecimal digits, where letters MAY be upper-case but lower-
case characters are RECOMMENDED.
When defining a type derived (directly or indirectly) from the
Integer32 base type, the set of possible values may be restricted by
appending a list of ranges or explicit values, separated by pipe `|'
characters and the whole list enclosed in parenthesis. A range
consists of a lower bound, two consecutive dots `..' and an upper
bound. Each value can be given in decimal or `0x'-prefixed
hexadecimal notation. Hexadecimal numbers must have an even number
of at least two digits. If multiple values or ranges are given they
all MUST be disjoint and MUST be in ascending order. If a value
restriction is applied to an already restricted type the new
restriction MUST be equal or more limiting, that is raising the lower
bounds, reducing the upper bounds, removing explicit values or
ranges, or splitting ranges into multiple ranges with intermediate
gaps.
Value Examples:
015 // illegal leading zero
-123 // legal negative value
- 1 // illegal intermediate space
0xabc // illegal hexadecimal value length
-0xff // illegal sign on hex value
0x80000000 // illegal value, too large
0xf00f // legal hexadecimal value
Restriction Examples:
Integer32 (0 | 5..10) // legal range spec
Integer32 (5..10 | 2..3) // illegal ordering
Integer32 (4..8 | 5..10) // illegal overlapping
3.5 Integer64
The Integer64 base type represents integer values between -2^63 (-
9223372036854775808) and 2^63-1 (9223372036854775807).
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Values of type Integer64 may be denoted as decimal or hexadecimal
numbers, where only decimal numbers can be negative. Decimal numbers
other than zero MUST NOT have leading zero digits. Hexadecimal
numbers are prefixed by `0x' and MUST have an even number of
hexadecimal digits, where letters MAY be upper-case but lower-case
characters are RECOMMENDED.
When defining a type derived (directly or indirectly) from the
Integer64 base type, the set of possible values may be restricted by
appending a list of ranges or explicit values, separated by pipe `|'
characters and the whole list enclosed in parenthesis. A range
consists of a lower bound, two consecutive dots `..' and an upper
bound. Each value can be given in decimal or `0x'-prefixed
hexadecimal notation. Hexadecimal numbers must have an even number
of at least two digits. If multiple values or ranges are given they
all MUST be disjoint and MUST be in ascending order. If a value
restriction is applied to an already restricted type the new
restriction MUST be equal or more limiting, that is raising the lower
bounds, reducing the upper bounds, removing explicit values or
ranges, or splitting ranges into multiple ranges with intermediate
gaps.
Value Examples:
015 // illegal leading zero
-123 // legal negative value
- 1 // illegal intermediate space
0xabc // illegal hexadecimal value length
-0xff // illegal sign on hex value
0x80000000 // legal value
Restriction Examples:
Integer64 (0 | 5..10) // legal range spec
Integer64 (5..10 | 2..3) // illegal ordering
Integer64 (4..8 | 5..10) // illegal overlapping
3.6 Unsigned32
The Unsigned32 base type represents positive integer values between 0
and 2^32-1 (4294967295).
Values of type Unsigned32 may be denoted as decimal or hexadecimal
numbers. Decimal numbers other than zero MUST NOT have leading zero
digits. Hexadecimal numbers are prefixed by `0x' and MUST have an
even number of hexadecimal digits, where letters MAY be upper-case
but lower-case characters are RECOMMENDED.
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When defining a type derived (directly or indirectly) from the
Unsigned32 base type, the set of possible values may be restricted by
appending a list of ranges or explicit values, separated by pipe `|'
characters and the whole list enclosed in parenthesis. A range
consists of a lower bound, two consecutive dots `..' and an upper
bound. Each value can be given in decimal or `0x'-prefixed
hexadecimal notation. Hexadecimal numbers must have an even number
of at least two digits. If multiple values or ranges are given they
all MUST be disjoint and MUST be in ascending order. If a value
restriction is applied to an already restricted type the new
restriction MUST be equal or more limiting, that is raising the lower
bounds, reducing the upper bounds, removing explicit values or
ranges, or splitting ranges into multiple ranges with intermediate
gaps.
Value Examples:
015 // illegal leading zero
-123 // illegal negative value
0xabc // illegal hexadecimal value length
0x80000000 // legal hexadecimal value
0x8080000000 // illegal value, too large
Restriction Examples:
Unsigned32 (0 | 5..10) // legal range spec
Unsigned32 (5..10 | 2..3) // illegal ordering
Unsigned32 (4..8 | 5..10) // illegal overlapping
3.7 Unsigned64
The Unsigned64 base type represents positive integer values between 0
and 2^64-1 (18446744073709551615).
Values of type Unsigned64 may be denoted as decimal or hexadecimal
numbers. Decimal numbers other than zero MUST NOT have leading zero
digits. Hexadecimal numbers are prefixed by `0x' and MUST have an
even number of hexadecimal digits, where letters MAY be upper-case
but lower-case characters are RECOMMENDED.
When defining a type derived (directly or indirectly) from the
Unsigned64 base type, the set of possible values may be restricted by
appending a list of ranges or explicit values, separated by pipe `|'
characters and the whole list enclosed in parenthesis. A range
consists of a lower bound, two consecutive dots `..' and an upper
bound. Each value can be given in decimal or `0x'-prefixed
hexadecimal notation. Hexadecimal numbers must have an even number
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of at least two digits. If multiple values or ranges are given they
all MUST be disjoint and MUST be in ascending order. If a value
restriction is applied to an already restricted type the new
restriction MUST be equal or more limiting, that is raising the lower
bounds, reducing the upper bounds, removing explicit values or
ranges, or splitting ranges into multiple ranges with intermediate
gaps.
Value Examples:
015 // illegal leading zero
-123 // illegal negative value
0xabc // illegal hexadecimal value length
0x8080000000 // legal hexadecimal value
Restriction Examples:
Unsigned64 (1..10000000000) // legal range spec
Unsigned64 (5..10 | 2..3) // illegal ordering
3.8 Float32
The Float32 base type represents floating point values of single
precision as described by [15].
Values of type Float32 may be denoted as a decimal fraction with an
optional exponent as known from many programming languages. See the
grammar rule `floatValue' of Appendix A for the detailed syntax.
Special values are `snan' (signaling Not-a-Number), `qnan' (quiet
Not-a-Number), `neginf' (negative infinity), and `posinf' (positive
infinity). Note that -0.0 and +0.0 are different floating point
values. 0.0 is equal to +0.0.
When defining a type derived (directly or indirectly) from the
Float32 base type, the set of possible values may be restricted by
appending a list of ranges or explicit values, separated by pipe `|'
characters and the whole list enclosed in parenthesis. A range
consists of a lower bound, two consecutive dots `..' and an upper
bound. If multiple values or ranges are given they all MUST be
disjoint and MUST be in ascending order. If a value restriction is
applied to an already restricted type the new restriction MUST be
equal or more limiting, that is raising the lower bounds, reducing
the upper bounds, removing explicit values or ranges, or splitting
ranges into multiple ranges with intermediate gaps. The special
values `snan', `qnan', `neginf', and `posinf' must be explicitly
listed in restrictions if they shall be included, where `snan' and
`qnan' cannot be used in ranges.
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Note that encoding is not subject to this specification. It has to
be described by protocols that transport objects of type Float32.
Note also that most floating point encodings disallow the
representation of many values that can be written as decimal
fractions as used in SMIng for human readability. Therefore,
explicit values in floating point type restrictions should be handled
with care.
Value Examples:
00.1 // illegal leading zero
3.1415 // legal value
-2.5E+3 // legal negative exponential value
Restriction Examples:
Float32 (-1.0..1.0) // legal range spec
Float32 (1 | 3.3 | 5) // legal, probably unrepresentable 3.3
Float32 (neginf..-0.0) // legal range spec
Float32 (-10.0..10.0 | 0) // illegal overlapping
3.9 Float64
The Float64 base type represents floating point values of double
precision as described by [15].
Values of type Float64 may be denoted as a decimal fraction with an
optional exponent as known from many programming languages. See the
grammar rule `floatValue' of Appendix A for the detailed syntax.
Special values are `snan' (signaling Not-a-Number), `qnan' (quiet
Not-a-Number), `neginf' (negative infinity), and `posinf' (positive
infinity). Note that -0.0 and +0.0 are different floating point
values. 0.0 is equal to +0.0.
When defining a type derived (directly or indirectly) from the
Float64 base type, the set of possible values may be restricted by
appending a list of ranges or explicit values, separated by pipe `|'
characters and the whole list enclosed in parenthesis. A range
consists of a lower bound, two consecutive dots `..' and an upper
bound. If multiple values or ranges are given they all MUST be
disjoint and MUST be in ascending order. If a value restriction is
applied to an already restricted type the new restriction MUST be
equal or more limiting, that is raising the lower bounds, reducing
the upper bounds, removing explicit values or ranges, or splitting
ranges into multiple ranges with intermediate gaps. The special
values `snan', `qnan', `neginf', and `posinf' must be explicitly
listed in restrictions if they shall be included, where `snan' and
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`qnan' cannot be used in ranges.
Note that encoding is not subject to this specification. It has to
be described by protocols that transport objects of type Float64.
Note also that most floating point encodings disallow the
representation of many values that can be written as decimal
fractions as used in SMIng for human readability. Therefore,
explicit values in floating point type restrictions should be handled
with care.
Value Examples:
00.1 // illegal leading zero
3.1415 // legal value
-2.5E+3 // legal negative exponential value
Restriction Examples:
Float64 (-1.0..1.0) // legal range spec
Float64 (1 | 3.3 | 5) // legal, probably unrepresentable 3.3
Float64 (neginf..-0.0) // legal range spec
Float64 (-10.0..10.0 | 0) // illegal overlapping
3.10 Float128
The Float128 base type represents floating point values of quadruple
precision as described by [15].
Values of type Float128 may be denoted as a decimal fraction with an
optional exponent as known from many programming languages. See the
grammar rule `floatValue' of Appendix A for the detailed syntax.
Special values are `snan' (signaling Not-a-Number), `qnan' (quiet
Not-a-Number), `neginf' (negative infinity), and `posinf' (positive
infinity). Note that -0.0 and +0.0 are different floating point
values. 0.0 is equal to +0.0.
When defining a type derived (directly or indirectly) from the
Float128 base type, the set of possible values may be restricted by
appending a list of ranges or explicit values, separated by pipe `|'
characters and the whole list enclosed in parenthesis. A range
consists of a lower bound, two consecutive dots `..' and an upper
bound. If multiple values or ranges are given they all MUST be
disjoint and MUST be in ascending order. If a value restriction is
applied to an already restricted type the new restriction MUST be
equal or more limiting, that is raising the lower bounds, reducing
the upper bounds, removing explicit values or ranges, or splitting
ranges into multiple ranges with intermediate gaps. The special
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values `snan', `qnan', `neginf', and `posinf' must be explicitly
listed in restrictions if they shall be included, where `snan' and
`qnan' cannot be used in ranges.
Note that encoding is not subject to this specification. It has to
be described by protocols that transport objects of type Float128.
Note also that most floating point encodings disallow the
representation of many values that can be written as decimal
fractions as used in SMIng for human readability. Therefore,
explicit values in floating point type restrictions should be handled
with care.
Value Examples:
00.1 // illegal leading zero
3.1415 // legal value
-2.5E+3 // legal negative exponential value
Restriction Examples:
Float128 (-1.0..1.0) // legal range spec
Float128 (1 | 3.3 | 5) // legal, probably unrepresentable 3.3
Float128 (neginf..-0.0) // legal range spec
Float128 (-10.0..10.0 | 0) // illegal overlapping
3.11 Enumeration
The Enumeration base type represents values from a set of integers in
the range between -2^31 (-2147483648) and 2^31-1 (2147483647), where
each value has an assigned name. The list of those named numbers has
to be comma-separated, enclosed in parenthesis and appended to the
`Enumeration' keyword. Each named number is denoted by its lower-
case identifier followed by the assigned integer value, denoted as a
decimal or `0x'-prefixed hexadecimal number, enclosed in parenthesis.
Hexadecimal numbers must have an even number of at least two digits.
Every name and every number in an enumeration type MUST be unique.
It is RECOMMENDED that values are positive and start at 1 and be
numbered contiguously. All named numbers MUST be given in ascending
order.
Values of enumeration types may be denoted as decimal or `0x'-
prefixed hexadecimal numbers or preferably as their assigned names.
Hexadecimal numbers must have an even number of at least two digits.
When defining a type derived (directly or indirectly) from an
enumeration type, the set of named numbers may be equal or restricted
by removing one or more named numbers. But no named numbers may be
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added or changed regarding its name, value, or both.
Type and Value Examples:
Enumeration (up(1), down(2), testing(3))
Enumeration (down(2), up(1)) // illegal order
0 // legal (though not recommended) value
up // legal value given by name
2 // legal value given by number
3.12 Bits
The Bits base type represents bit sets. That is, a Bits value is a
set of flags identified by small integer numbers starting at 0. Each
bit number has an assigned name. The list of those named numbers has
to be comma-separated, enclosed in parenthesis and appended to the
`Bits' keyword. Each named number is denoted by its lower-case
identifier followed by the assigned integer value, denoted as a
decimal or `0x'-prefixed hexadecimal number, enclosed in parenthesis.
Hexadecimal numbers must have an even number of at least two digits.
Every name and every number in a bits type MUST be unique. It is
RECOMMENDED that numbers start at 0 and be numbered contiguously.
Negative numbers are forbidden. All named numbers MUST be given in
ascending order.
Values of bits types may be denoted as a comma-separated list of
decimal or `0x'-prefixed hexadecimal numbers or preferably their
assigned names enclosed in parenthesis. Hexadecimal numbers must
have an even number of at least two digits. There MUST NOT be any
element (by name or number) listed more than once. Elements MUST be
listed in ascending order.
When defining a type derived (directly or indirectly) from a bits
type, the set of named numbers may be restricted by removing one or
more named numbers. But no named numbers may be added or changed
regarding its name, value, or both.
Type and Value Examples:
Bits (readable(0), writeable(1), executable(2))
Bits (writeable(1), readable(0) // illegal order
() // legal empty value
(readable, writeable, 2) // legal value
(0, readable, executable) // illegal, readable(0) appears twice
(writeable, 4) // illegal, element 4 out of range
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3.13 Display Formats
Attribute definitions and type definitions allow the specification of
a format to be used, when a value of that attribute or an attribute
of that type is displayed. Format specifications are represented as
textual data.
When the attribute or type has an underlying base type of Integer32,
Integer64, Unsigned32, or Unsigned64, the format consists of an
integer-format specification, containing two parts. The first part
is a single character suggesting a display format, either: `x' for
hexadecimal, or `d' for decimal, or `o' for octal, or `b' for binary.
For all types, when rendering the value, leading zeros are omitted,
and for negative values, a minus sign is rendered immediately before
the digits. The second part is always omitted for `x', `o' and `b',
and need not be present for `d'. If present, the second part starts
with a hyphen and is followed by a decimal number, which defines the
implied decimal point when rendering the value. For example `d-2'
suggests that a value of 1234 be rendered as `12.34'.
When the attribute or type has an underlying base type of
OctetString, the format consists of one or more octet-format
specifications. Each specification consists of five parts, with each
part using and removing zero or more of the next octets from the
value and producing the next zero or more characters to be displayed.
The octets within the value are processed in order of significance,
most significant first.
The five parts of a octet-format specification are:
1. the (optional) repeat indicator; if present, this part is a `*',
and indicates that the current octet of the value is to be used
as the repeat count. The repeat count is an unsigned integer
(which may be zero) which specifies how many times the remainder
of this octet-format specification should be successively
applied. If the repeat indicator is not present, the repeat
count is one.
2. the octet length: one or more decimal digits specifying the
number of octets of the value to be used and formatted by this
octet-specification. Note that the octet length can be zero. If
less than this number of octets remain in the value, then the
lesser number of octets are used.
3. the display format, either: `x' for hexadecimal, `d' for decimal,
`o' for octal, `a' for ASCII, or `t' for UTF-8 [16]. If the
octet length part is greater than one, and the display format
part refers to a numeric format, then network byte-ordering (big-
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endian encoding) is used interpreting the octets in the value.
The octets processed by the `t' display format do not necessarily
form an integral number of UTF-8 characters. Trailing octets
which do not form a valid UTF-8 encoded character are discarded.
4. the (optional) display separator character; if present, this part
is a single character which is produced for display after each
application of this octet-specification; however, this character
is not produced for display if it would be immediately followed
by the display of the repeat terminator character for this octet
specification. This character can be any character other than a
decimal digit and a `*'.
5. the (optional) repeat terminator character, which can be present
only if the display separator character is present and this octet
specification begins with a repeat indicator; if present, this
part is a single character which is produced after all the zero
or more repeated applications (as given by the repeat count) of
this octet specification. This character can be any character
other than a decimal digit and a `*'.
Output of a display separator character or a repeat terminator
character is suppressed if it would occur as the last character of
the display.
If the octets of the value are exhausted before all the octet format
specification have been used, then the excess specifications are
ignored. If additional octets remain in the value after interpreting
all the octet format specifications, then the last octet format
specification is re-interpreted to process the additional octets,
until no octets remain in the value.
Note that for some types no format specifications are defined and
SHOULD be omitted. Implementations MUST ignore format specifications
they cannot interpret. Also note that the SMIng grammar (Appendix A)
does not specify the syntax of format specifications.
Display Format Examples:
Base Type Format Example Value Rendered Value
----------- ------------------- ---------------- -----------------
OctetString 255a "Hello World." Hello World.
OctetString 1x: "Hello!" 48:65:6c:6c:6f:21
OctetString 1d:1d:1d.1d,1a1d:1d 0x0d1e0f002d0400 13:30:15.0,-4:0
OctetString 1d.1d.1d.1d/2d 0x0a0000010400 10.0.0.1/1024
OctetString *1x:/1x: 0x02aabbccddee aa:bb/cc:dd:ee
Integer32 d-2 1234 12.34
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4. The SMIng File Structure
The topmost container of SMIng information is a file. An SMIng file
may contain zero, one or more modules. It is RECOMMENDED to separate
modules into files named by their modules, where possible. Though,
for dedicated purposes it may be reasonable to collect several
modules in a single file.
The top level SMIng construct is the `module' statement (Section 5)
that defines a single SMIng module. A module contains a sequence of
sections in an obligatory order with different kinds of definitions.
Whether these sections contain statements or remain empty mainly
depends on the purpose of the module.
4.1 Comments
Comments can be included at any position in an SMIng file, except in
between the characters of a single token like those of a quoted
string. However, it is RECOMMENDED that all substantive descriptions
be placed within an appropriate description clause, so that the
information is available to SMIng parsers.
Comments commence with a pair of adjacent slashes `//' and end at the
end of the line.
4.2 Statements and Arguments
SMIng has a very small set of basic grammar rules based on the
concept of statements. Each statement starts with a lower-case
keyword identifying the statement followed by a number (possibly
zero) of arguments. An argument may be quoted text, an identifier, a
value of any base type, a list of identifiers enclosed in parenthesis
`( )' or a statement block enclosed in curly braces `{ }'. Since
statement blocks are valid arguments, it is possible to nest
statement sequences. Each statement is terminated by a semicolon
`;'.
The core set of statements may be extended using the SMIng
`extension' statement. See Section 6 and Section 11 for details.
At places where a statement is expected, but an unknown lower-case
word is read, those statements MUST be skipped up to the proper
semicolon, including nested statement blocks.
5. The module Statement
The `module' statement is used as a container of all definitions of a
single SMIng module. It gets two arguments: an upper-case module
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name and a statement block that contains mandatory and optional
statements and sections of statements in an obligatory order:
module <MODULE-NAME> {
<optional import statements>
<organization statement>
<contact statement>
<description statement>
<optional reference statement>
<at least one revision statement>
<optional extension statements>
<optional typedef statements>
<optional class statements>
};
The optional `import' statements are followed by the mandatory
`organization', `contact', and `description' statements and the
optional `reference' statement, which in turn are followed by the
mandatory `revision' statements. This part defines the module's meta
information while the following sections contain its main
definitions.
See the `moduleStatement' rule of the SMIng grammar (Appendix A) for
the formal syntax of the `module' statement.
5.1 The module's import Statement
The optional module's `import' statement is used to import
identifiers from external modules into the local module's namespace.
It gets two arguments: the name of the external module and a comma-
separated list of one or more identifiers to be imported enclosed in
parenthesis.
Multiple `import' statements for the same module but with disjoint
lists of identifiers are allowed, though NOT RECOMMENDED. Anyhow,
the same identifier from the same module MUST NOT be imported
multiple times. To import identifiers with the same name from
different modules might be necessary and is allowed. To distinguish
them in the local module, they have to be referred by qualified
names. It is NOT RECOMMENDED to import identifiers not used in the
local module.
See the `importStatement' rule of the SMIng grammar (Appendix A) for
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the formal syntax of the `import' statement.
5.2 The module's organization Statement
The module's `organization' statement, which must be present, gets
one argument which is used to specify a textual description of the
organization(s) under whose auspices this module was developed.
5.3 The module's contact Statement
The module's `contact' statement, which must be present, gets one
argument which is used to specify the name, postal address, telephone
number, and electronic mail address of the person to whom technical
queries concerning this module should be sent.
5.4 The module's description Statement
The module's `description' statement, which must be present, gets one
argument which is used to specify a high-level textual description of
the contents of this module.
5.5 The module's reference Statement
The module's `reference' statement, which need not be present, gets
one argument which is used to specify a textual cross-reference to
some other document, either another module which defines related
management information, or some other document which provides
additional information relevant to this module.
5.6 The module's revision Statement
The module's `revision' statement is repeatedly used to specify the
editorial revisions of the module, including the initial revision.
It gets one argument which is a statement block that holds detailed
information in an obligatory order. A module MUST have at least one
initial `revision' statement. For every editorial change, a new one
MUST be added in front of the revisions sequence, so that all
revisions are in reverse chronological order.
See the `revisionStatement' rule of the SMIng grammar (Appendix A)
for the formal syntax of the `revision' statement.
5.6.1 The revision's date Statement
The revision's `date' statement, which must be present, gets one
argument which is used to specify the date and time of the revision
in the format `YYYY-MM-DD HH:MM' or `YYYY-MM-DD' which implies the
time `00:00'. The time is always given in UTC.
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See the `date' rule of the SMIng grammar (Appendix A) for the formal
syntax of the revision's `date' statement.
5.6.2 The revision's description Statement
The revision's `description' statement, which must be present, gets
one argument which is used to specify a high-level textual
description of the revision.
5.7 Usage Example
Consider how a skeletal module might be constructed:
module FIZBIN {
import IETF-SMING (DisplayString);
organization
"IETF Next Generation Structure of
Management Information Working Group (SMING)";
contact
"Frank Strauss
TU Braunschweig
Bueltenweg 74/75
38106 Braunschweig
Germany
Phone: +49 531 391-3266
EMail: strauss@ibr.cs.tu-bs.de";
description
"The module for entities implementing
the xxxx protocol.";
reference
"RFC 2578, Section 5.7.";
revision {
date "2001-03-02";
description
"Initial revision, published as RFC XXXX.";
};
// ... further definitions ...
}; // end of module FIZBIN.
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6. The extension Statement
The `extension' statement is used to define new statements to be used
in the local module following this extension statement definition or
in external modules that may import this extension statement
definition. The `extension' statement gets two arguments: a lower-
case extension statement identifier and a statement block that holds
detailed extension information in an obligatory order.
Extension statement identifiers SHOULD NOT contain any upper-case
characters.
Note that the SMIng extension feature does not allow to formally
specify the context, argument syntax and semantics of an extension.
Its only purpose is to declare the existence of an extension and to
allow a unique reference to an extension. See Section 11 for
detailed information on extensions and [3] for mappings of SMIng
definitions to SNMP which is formally defined as an extension.
See the `extensionStatement' rule of the SMIng grammar (Appendix A)
for the formal syntax of the `extension' statement.
6.1 The extension's status Statement
The extension's `status' statement, which must be present, gets one
argument which is used to specify whether this extension definition
is current or historic. The value `current' means that the
definition is current and valid. The value `obsolete' means the
definition is obsolete and should not be implemented and/or can be
removed if previously implemented. While the value `deprecated' also
indicates an obsolete definition, it permits new/continued
implementation in order to foster interoperability with
older/existing implementations.
6.2 The extension's description Statement
The extension's `description' statement, which must be present, gets
one argument which is used to specify a high-level textual
description of the extension statement.
It is RECOMMENDED to include information on the extension's context,
its semantics, and implementation conditions. See also Section 11.
6.3 The extension's reference Statement
The extension's `reference' statement, which need not be present,
gets one argument which is used to specify a textual cross-reference
to some other document, either another module which defines related
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extension definitions, or some other document which provides
additional information relevant to this extension.
6.4 The extension's abnf Statement
The extension's `abnf' statement, which need not be present, gets one
argument which is used to specify a formal ABNF [12] grammar
definition of the extension. This grammar can reference rule names
from the core SMIng grammar Appendix A.
Note that the `abnf' statement should contain only pure ABNF and no
additional text, though comments prefixed by semicolon are allowed
but should probably be moved to the description statement. Note that
double quotes are not allowed inside textual descriptions which are
itself enclosed in double quotes. So they have to be replaced by
single quotes.
6.5 Usage Example
extension severity {
status current;
description
"The optional severity extension statement can only
be applied to the statement block of an SMIng class'
event definition. If it is present it denotes the
severity level of the event in a range from 0
(emergency) to 7 (debug).";
abnf
"severityStatement = severityKeyword sep number optsep ';'
severityKeyword = 'severity'";
};
7. The typedef Statement
The `typedef' statement is used to define new data types to be used
in the local module or in external modules. It gets two arguments:
an upper-case type identifier and a statement block that holds
detailed type information in an obligatory order.
Type identifiers SHOULD NOT consist of all upper-case characters and
SHOULD NOT contain hyphens.
See the `typedefStatement' rule of the SMIng grammar (Appendix A) for
the formal syntax of the `typedef' statement.
7.1 The typedef's type Statement
The typedef's `type' statement, which must be present, gets one
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argument which is used to specify the type from which this type is
derived. Optionally, type restrictions may be applied to the new
type by appending subtyping information according to the rules of the
base type. See Section 3 for SMIng base types and their type
restrictions.
7.2 The typedef's default Statement
The typedef's `default' statement, which need not be present, gets
one argument which is used to specify an acceptable default value for
attributes of this type. A default value may be used when an
attribute instance is created. That is, the value is a "hint" to
implementors.
The value of the `default' statement must, of course, correspond to
the (probably restricted) type specified in the typedef's `type'
statement.
The default value of a type may be overwritten by a default value of
an attribute of this type.
Note that for some types, default values make no sense.
7.3 The typedef's format Statement
The typedef's `format' statement, which need not be present, gets one
argument which is used to give a hint as to how the value of an
instance of an attribute of this type might be displayed. See
Section 3.13 for a description of format specifications.
If no format is specified, it is inherited from the type given in the
`type' statement. On the other hand, the format specification of a
type may be semantically refined by a format specification of an
attribute of this type.
7.4 The typedef's units Statement
The typedef's `units' statement, which need not be present, gets one
argument which is used to specify a textual definition of the units
associated with attributes of this type.
If no units are specified, they are inherited from the type given in
the `type' statement. On the other hand, the units specification of
a type may be semantically refined by a units specification of an
attribute of this type.
The units specification has to be appropriate for values displayed
according to the typedef's format specification, if present. E.g.,
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if the type defines frequency values of type Unsigned64 measured in
thousands of Hertz, the format specification should be `d-3' and the
units specification should be `Hertz' or `Hz'. If the format
specification would be omitted, the units specification should be
`Milli-Hertz' or `mHz'. Authors of SMIng modules should pay
attention to keep format and units specifications synced.
Application implementors MUST NOT implement units specifications
without implementing format specifications.
7.5 The typedef's status Statement
The typedef's `status' statement, which must be present, gets one
argument which is used to specify whether this type definition is
current or historic. The value `current' means that the definition
is current and valid. The value `obsolete' means the definition is
obsolete and should not be implemented and/or can be removed if
previously implemented. While the value `deprecated' also indicates
an obsolete definition, it permits new/continued implementation in
order to foster interoperability with older/existing implementations.
Derived types SHOULD NOT be defined as `current' if their underlying
type is `deprecated' or `obsolete'. Similarly, they SHOULD NOT be
defined as `deprecated' if their underlying type is `obsolete'.
Nevertheless, subsequent revisions of the underlying type cannot be
avoided, but SHOULD be taken into account in subsequent revisions of
the local module.
7.6 The typedef's description Statement
The typedef's `description' statement, which must be present, gets
one argument which is used to specify a high-level textual
description of the newly defined type.
It is RECOMMENDED to include all semantic definitions necessary for
implementation, and to embody any information which would otherwise
be communicated in any commentary annotations associated with this
type definition.
7.7 The typedef's reference Statement
The typedef's `reference' statement, which need not be present, gets
one argument which is used to specify a textual cross-reference to
some other document, either another module which defines related type
definitions, or some other document which provides additional
information relevant to this type definition.
7.8 Usage Examples
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typedef RptrOperStatus {
type Enumeration (other(1), ok(2), rptrFailure(3),
groupFailure(4), portFailure(5),
generalFailure(6));
default other; // undefined by default.
status deprecated;
description
"A type to indicate the operational state
of a repeater.";
reference
"[IEEE 802.3 Mgt], 30.4.1.1.5, aRepeaterHealthState.";
};
typedef SnmpTransportDomain {
type Pointer (snmpTransportDomain);
status current;
description
"A pointer to an SNMP transport domain identity.";
};
typedef DateAndTime {
type OctetString (8 | 11);
format "2d-1d-1d,1d:1d:1d.1d,1a1d:1d";
status current;
description
"A date-time specification.
...
Note that if only local time is known, then timezone
information (fields 8-10) is not present.";
reference
"RFC 2579, SNMPv2-TC.DateAndTime.";
};
typedef Frequency {
type Unsigned64;
format "d-3"
units "Hertz";
status current;
description
"A wide-range frequency specification measured
in thousands of Hertz.";
};
8. The identity Statement
The `identity' statement is used to define a new abstract and untyped
identity. Its only purpose is to denote its name, semantics and
existence. An identity can be defined either from scratch or derived
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from a parent identity. The `identity' statement gets the following
two or four arguments: The first argument is a lower-case identity
identifier and the last argument is a statement block that holds
detailed identity information in an obligatory order. In case of
derived identities there are two tokens inbetween: a single colon `:'
and the identifier of the parent identity.
See the `identityStatement' rule of the SMIng grammar (Appendix A)
for the formal syntax of the `identity' statement.
8.1 The identity's status Statement
The identity's `status' statement, which must be present, gets one
argument which is used to specify whether this identity definition is
current or historic. The value `current' means that the definition
is current and valid. The value `obsolete' means the definition is
obsolete and should not be implemented and/or can be removed if
previously implemented. While the value `deprecated' also indicates
an obsolete definition, it permits new/continued implementation in
order to foster interoperability with older/existing implementations.
Derived identities SHOULD NOT be defined as `current' if their parent
identity is `deprecated' or `obsolete'. Similarly, they SHOULD NOT
be defined as `deprecated' if their parent identity is `obsolete'.
Nevertheless, subsequent revisions of the parent identity cannot be
avoided, but SHOULD be taken into account in subsequent revisions of
the local module.
8.2 The identity' description Statement
The identity's `description' statement, which must be present, gets
one argument which is used to specify a high-level textual
description of the newly defined identity.
It is RECOMMENDED to include all semantic definitions necessary for
implementation, and to embody any information which would otherwise
be communicated in any commentary annotations associated with this
identity definition.
8.3 The identity's reference Statement
The identity's `reference' statement, which need not be present, gets
one argument which is used to specify a textual cross-reference to
some other document, either another module which defines related
identity definitions, or some other document which provides
additional information relevant to this identity definition.
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8.4 Usage Examples
identity null {
status current;
description
"An identity used to represent null pointer values.";
};
identity snmpTransportDomain {
status current;
description
"A generic SNMP transport domain identity.";
};
identity snmpUDPDomain : snmpTransportDomain {
status current;
description
"The SNMP over UDP transport domain.";
};
9. The class Statement
The `class' statement is used to define a new class, that represents
a container of related attributes and events (Section 9.1, Section
9.3) in an object-oriented manner. Thus, a class can be defined
either from scratch or derived from a parent class. A derived class
inherits all attributes and events of the parent class and can be
extended by additional attributes and events. Furthermore, parent
attributes can be refined by new attributes of the same name that are
more specific in their formal type restrictions or their semantics
specified in the attribute description clause. Similarly, parent
events can be refined by new events of the same name that are more
specific in their semantics specified in the event description
clause.
The `class' statement gets the following two or four arguments: The
first argument is an upper-case class identifier and the last
argument is a statement block that holds detailed class information
in an obligatory order. In case of derived classes there are two
tokens inbetween: a single colon `:' and the identifier of the parent
class.
See the `classStatement' rule of the SMIng grammar (Appendix A) for
the formal syntax of the `class' statement.
9.1 The class' attribute Statement
The class' `attribute' statement, which can be present zero, one or
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multiple times, gets three arguments: a type or class name, the
attribute name, and a statement block that holds detailed attribute
information in an obligatory order.
9.1.1 The attribute's access Statement
The attribute's `access' statement must be present for attributes
typed by a base type or derived type, and must be absent for
attributes typed by a class. It gets one argument which is used to
specify whether it makes sense to read and/or write an instance of
the attribute, or to include its value in an event. This is the
maximal level of access for the attribute. This maximal level of
access is independent of any administrative authorization policy.
The value `readwrite' indicates that read and write access makes
sense. The value `readonly' indicates that read access makes sense,
but write access is never possible. The value `eventonly' indicates
an object which is accessible only via an event.
These values are ordered, from least to greatest access level:
`eventonly', `readonly', `readwrite'.
9.1.2 The attribute's default Statement
The attribute's `default' statement need not be present for
attributes typed by a base type or derived type, and must be absent
for attributes typed by a class. It gets one argument which is used
to specify an acceptable default value for this attribute. A default
value may be used when an attribute instance is created. That is,
the value is a "hint" to implementors.
The value of the `default' statement must, of course, correspond to
the (probably restricted) type specified in the attribute's `type'
statement.
The attribute's default value overrides the default value of the
underlying type definition if both are present.
9.1.3 The attribute's format Statement
The attribute's `format' statement need not be present for attributes
typed by a base type or derived type, and must be absent for
attributes typed by a class. It gets one argument which is used to
give a hint as to how the value of an instance of this attribute
might be displayed. See Section 3.13 for a description of format
specifications.
The attribute's format specification overrides the format
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specification of the underlying type definition if both are present.
9.1.4 The attribute's units Statement
The attribute's `units' statement need not be present for attributes
typed by a base type or derived type, and must be absent for
attributes typed by a class. It gets one argument which is used to
specify a textual definition of the units associated with this
attribute.
The attribute's units specification overrides the units specification
of the underlying type definition if both are present.
The units specification has to be appropriate for values displayed
according to the attribute's format specification if present. E.g.,
if the attribute represents a frequency value of type Unsigned64
measured in thousands of Hertz, the format specification should be
`d-3' and the units specification should be `Hertz' or `Hz'. If the
format specification would be omitted the units specification should
be `Milli-Hertz' or `mHz'. Authors of SMIng modules should pay
attention to keep format and units specifications of type and
attribute definitions synced. Application implementors MUST NOT
implement units specifications without implementing format
specifications.
9.1.5 The attribute's status Statement
The attribute's `status' statement must be present for attributes
typed by a base type or derived type, and must be absent for
attributes typed by a class. It gets one argument which is used to
specify whether this attribute definition is current or historic.
The value `current' means that the definition is current and valid.
The value `obsolete' means the definition is obsolete and should not
be implemented and/or can be removed if previously implemented.
While the value `deprecated' also indicates an obsolete definition,
it permits new/continued implementation in order to foster
interoperability with older/existing implementations.
Attributes SHOULD NOT be defined as `current' if their type or their
containing class is `deprecated' or `obsolete'. Similarly, they
SHOULD NOT be defined as `deprecated' if their type or their
containting class is `obsolete'. Nevertheless, subsequent revisions
of used type definition cannot be avoided, but SHOULD be taken into
account in subsequent revisions of the local module.
9.1.6 The attribute's description Statement
The attribute's `description' statement, which must be present, gets
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one argument which is used to specify a high-level textual
description of this attribute.
It is RECOMMENDED to include all semantic definitions necessary for
the implementation of this attribute.
9.1.7 The attribute's reference Statement
The attribute's `reference' statement, which need not be present,
gets one argument which is used to specify a textual cross-reference
to some other document, either another module which defines related
attribute definitions, or some other document which provides
additional information relevant to this attribute definition.
9.2 The class' unique Statement
The class' `unique' statement, which need not be present, gets one
argument that specifies a comma-separated list of attributes of this
class, enclosed in parenthesis. If present, this list of attributes
makes up a unique identification of all possible instances of this
class. It can be used as a unique key in underlying protocols.
If the list is empty the class should be regarded as a scalar class
with only a single static instance.
If the `unique' statement is not present the class is not meant to be
instantiated directly, but just to be contained in other classes or
to be the parent class of other refining classes.
If present, the attribute list MUST NOT contain any attribute more
than once and the attributes should be ordered where appropriate so
that the attributes that are most significant in most situations
appear first.
9.3 The class' event Statement
The class' `event' statement is used to define an event related to an
instance of this class that can occur asynchronously. It gets two
arguments: a lower-case event identifier and a statement block that
holds detailed information in an obligatory order.
See the `eventStatement' rule of the SMIng grammar (Appendix A) for
the formal syntax of the `event' statement.
9.3.1 The event's status Statement
The event's `status' statement, which must be present, gets one
argument which is used to specify whether this event definition is
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current or historic. The value `current' means that the definition
is current and valid. The value `obsolete' means the definition is
obsolete and should not be implemented and/or can be removed if
previously implemented. While the value `deprecated' also indicates
an obsolete definition, it permits new/continued implementation in
order to foster interoperability with older/existing implementations.
9.3.2 The event's description Statement
The event's `description' statement, which must be present, gets one
argument which is used to specify a high-level textual description of
this event.
It is RECOMMENDED to include all semantic definitions necessary for
the implementation of this event. In particular, it SHOULD be
documented which instance of the class is associated with an event of
this type.
9.3.3 The event's reference Statement
The event's `reference' statement, which need not be present, gets
one argument which is used to specify a textual cross-reference to
some other document, either another module which defines related
event definitions, or some other document which provides additional
information relevant to this event definition.
9.4 The class' status Statement
The class' `status' statement, which must be present, gets one
argument which is used to specify whether this class definition is
current or historic. The value `current' means that the definition
is current and valid. The value `obsolete' means the definition is
obsolete and should not be implemented and/or can be removed if
previously implemented. While the value `deprecated' also indicates
an obsolete definition, it permits new/continued implementation in
order to foster interoperability with older/existing implementations.
Derived classes SHOULD NOT be defined as `current' if their parent
class is `deprecated' or `obsolete'. Similarly, they SHOULD NOT be
defined as `deprecated' if their parent class is `obsolete'.
Nevertheless, subsequent revisions of the parent class cannot be
avoided, but SHOULD be taken into account in subsequent revisions of
the local module.
9.5 The class' description Statement
The class' `description' statement, which must be present, gets one
argument which is used to specify a high-level textual description of
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the newly defined class.
It is RECOMMENDED to include all semantic definitions necessary for
implementation, and to embody any information which would otherwise
be communicated in any commentary annotations associated with this
class definition.
9.6 The class's reference Statement
The class's `reference' statement, which need not be present, gets
one argument which is used to specify a textual cross-reference to
some other document, either another module which defines related
class definitions, or some other document which provides additional
information relevant to this class definition.
9.7 Usage Example
Consider how an event might be described that signals a status change
of an interface:
class Interface {
// ...
attribute Gauge32 speed {
access readonly;
units "bps";
status current;
description
"An estimate of the interface's current bandwidth
in bits per second.";
};
// ...
attribute AdminStatus adminStatus {
access readwrite;
status current;
description
"The desired state of the interface.";
};
attribute OperStatus operStatus {
access readonly;
status current;
description
"The current operational state of the interface.";
};
event linkDown {
status current;
description
"A linkDown event signifies that the ifOperStatus
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attribute for this interface instance is about to
enter the down state from some other state (but not
from the notPresent state). This other state is
indicated by the included value of ifOperStatus.";
};
status current;
description
"A physical or logical network interface.";
};
10. Extending a Module
As experience is gained with a module, it may be desirable to revise
that module. However, changes are not allowed if they have any
potential to cause interoperability problems between an
implementation using an original specification and an implementation
using an updated specification(s).
For any change, some statements near the top of the module MUST be
updated to include information about the revision: specifically, a
new `revision' statement (Section 5.6) must be included in front of
the `revision' statements. Furthermore, any necessary changes MUST
be applied to other statements, including the `organization' and
`contact' statements (Section 5.2, Section 5.3).
Note that any definition contained in a module is available to be
imported by any other module, and is referenced in an `import'
statement via the module name. Thus, a module name MUST NOT be
changed. Specifically, the module name (e.g., `FIZBIN' in the
example of Section 5.7) MUST NOT be changed when revising a module
(except to correct typographical errors), and definitions MUST NOT be
moved from one module to another.
Also note, that obsolete definitions MUST NOT be removed from modules
since their identifiers may still be referenced by other modules.
A definition may be revised in any of the following ways:
o In `typedef' statement blocks, a `type' statement containing an
`Enumeration' or `Bits' type may have new named numbers added.
o In `typedef' statement blocks, the value of a `type' statement may
be replaced by another type if the new type is derived (directly
or indirectly) from the same base type, has the same set of
values, and has identical semantics.
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o In `attribute' statements where the first argument specifies a
class, the class may be replaced by another class if the new class
is inherited (directly or indirectly) from the base class and both
classes have identical semantics.
o In `attribute' statements where the first argument specifies a
type, the type may be replaced by another type if the new type is
derived (directly or indirectly) from the same base type, has the
same set of values, and has identical semantics.
o In any statement block, a `status' statement value of `current'
may be revised as `deprecated' or `obsolete'. Similarly, a
`status' statement value of `deprecated' may be revised as
`obsolete'. When making such a change, the `description'
statement SHOULD be updated to explain the rationale.
o In `typedef' and `attribute' statement blocks, a `default'
statement may be added or updated.
o In `typedef' and `attribute' statement blocks, a `units' statement
may be added.
o A class may be augmented by adding new attributes.
o In any statement block, clarifications and additional information
may be included in the `description' statement.
o In any statement block, a `reference' statement may be added or
updated.
o Entirely new extensions, types, identities, and classes may be
defined, using previously unassigned identifiers.
Otherwise, if the semantics of any previous definition are changed
(i.e., if a non-editorial change is made to any definition other than
those specifically allowed above), then this MUST be achieved by a
new definition with a new identifier. In case of a class where the
semantics of any attributes are changed, the new class can be defined
by inheritence from the old class and refining the changed
attributes.
Note that changing the identifier associated with an existing
definition is considered a semantic change, as these strings may be
used in an `import' statement.
11. SMIng Language Extensibility
While the core SMIng language has a well defined set of statements
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(Section 5 through Section 9.3) that are used to specify those
aspects of management information commonly regarded as necessary
without management protocol specific information, there may be
further information, people wish to express. To describe additional
information informally in description statements has the disadvantage
that this information cannot be parsed by any program.
SMIng allows modules to include statements that are unknown to a
parser but fulfill some core grammar rules (Section 4.2).
Furthermore, additional statements may be defined by the `extension'
statement (Section 6). Extensions can be used in the local module or
in other modules, that import the extension. This has some
advantages:
o A parser can differentiate between statements known as extensions
and unknown statements. This enables the parser to complain about
unknown statements, e.g. due to typos.
o If an extension's definition contains a formal ABNF grammar
definition and a parser is able to interpret this ABNF definition,
this enables the parser also to complain about wrong usage of an
extension.
o Since, there might be some common need for extensions, there is a
relatively high probability of extension name collisions
originated by different organizations, as long as there is no
standardized extension for that purpose. The requirement to
explicitly import extension statements allows to distinguish those
extensions.
o The supported extensions of an SMIng implementation, e.g. a SMIng
module compiler, can be clearly expressed.
The only formal effect of an extension statement definition is to
declare its existence and its status, and optionally its ABNF
grammar. All additional aspects SHOULD be described in the
`description' statement:
o The detailed semantics of the new statement SHOULD be described.
o The contexts in which the new statement can be used, SHOULD be
described, e.g., a new statement may be designed to be used only
in the statement block of a module, but not in other nested
statement blocks. Others may be applicable in multiple contexts.
In addition, the point in the sequence of an obligatory order of
other statements, where the new statement may be inserted, might
be prescribed.
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o The circumstances that make the new statement mandatory or
optional SHOULD be described.
o The syntax of the new statement SHOULD at least be described
informally, if not supplied formally in an `abnf' statement.
o It might be reasonable to give some suggestions under which
conditions the implementation of the new statement is adequate and
how it could be integrated into existent implementations.
Some possible extension applications are:
o The formal mappings of SMIng definitions into the SNMP ([3]) and
COPS-PR frameworks are defined as SMIng extensions.
o Inlined annotations to definitions. E.g., a vendor may wish to
describe additional information to class and attribute definitions
in private modules. An example are severity levels of events in
the statement block of an `event' statement.
o Arbitrary annotations to external definitions. E.g., a vendor may
wish to describe additional information to definitions in a
"standard" module. This allows a vendor to implement "standard"
modules as well as additional private features, without redundant
module definitions, but on top of "standard" module definitions.
12. Security Considerations
This document defines a language with which to write and read
descriptions of management information. The language itself has no
security impact on the Internet.
13. Acknowledgements
Since SMIng started as a close successor of SMIv2, some paragraphs
and phrases are directly taken from the SMIv2 specifications [5],
[6], [7] written by Jeff Case, Keith McCloghrie, David Perkins,
Marshall T. Rose, Juergen Schoenwaelder, and Steven L. Waldbusser.
The authors would like to thank all participants of the 7th NMRG
meeting held in Schloss Kleinheubach from 6-8 September 2000, which
was a major step towards the current status of this memo, namely
Heiko Dassow, David Durham, and Bert Wijnen.
Marshall T. Rose's work on an XML framework for RFC authors [17]
made the writing of an Internet standards document much more
comfortable.
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References
[1] Strauss, F. and J. Schoenwaelder, "SMIng Core Modules", draft-
ietf-sming-modules-02.txt, July 2001.
[2] Strauss, F. and J. Schoenwaelder, "SMIng Internet Protocol Core
Modules", draft-ietf-sming-inet-modules-02.txt, July 2001.
[3] Strauss, F. and J. Schoenwaelder, "SMIng Extension for SNMP
Mappings", draft-ietf-sming-snmp-02.txt, July 2001.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, BCP 14, March 1997.
[5] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
M. and S. Waldbusser, "Structure of Management Information
Version 2 (SMIv2)", RFC 2578, STD 58, April 1999.
[6] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
M. and S. Waldbusser, "Textual Conventions for SMIv2", RFC
2579, STD 59, April 1999.
[7] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
M. and S. Waldbusser, "Conformance Statements for SMIv2", RFC
2580, STD 60, April 1999.
[8] McCloghrie, K., Fine, M., Seligson, J., Chan, K., Hahn, S.,
Sahita, R., Smith, A. and F. Reichmeyer, "Structure of Policy
Provisioning Information (SPPI)", draft-ietf-rap-sppi-07.txt,
May 2001.
[9] Rose, M. and K. McCloghrie, "Structure and Identification of
Management Information for TCP/IP-based Internets", RFC 1155,
STD 16, May 1990.
[10] Rose, M. and K. McCloghrie, "Concise MIB Definitions", RFC
1212, STD 16, March 1991.
[11] Rose, M., "A Convention for Defining Traps for use with the
SNMP", RFC 1215, March 1991.
[12] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[13] International Organization for Standardization, "Specification
of Abstract Syntax Notation One (ASN.1)", International
Standard 8824, December 1987.
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[14] Harrington, D., Presuhn, R. and B. Wijnen, "An Architecture for
Describing SNMP Management Frameworks", RFC 2271, January 1999.
[15] Institute of Electrical and Electronics Engineers, "IEEE
Standard for Binary Floating-Point Arithmetic", ANSI/IEEE
Standard 754-1985, August 1985.
[16] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC
2279, January 1998.
[17] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, June
1999.
Authors' Addresses
Frank Strauss
TU Braunschweig
Bueltenweg 74/75
38106 Braunschweig
Germany
Phone: +49 531 391-3266
EMail: strauss@ibr.cs.tu-bs.de
URI: http://www.ibr.cs.tu-bs.de/
Juergen Schoenwaelder
TU Braunschweig
Bueltenweg 74/75
38106 Braunschweig
Germany
Phone: +49 531 391-3289
EMail: schoenw@ibr.cs.tu-bs.de
URI: http://www.ibr.cs.tu-bs.de/
Appendix A. SMIng ABNF Grammar
The SMIng grammar conforms to the Augmented Backus-Naur Form (ABNF)
[12].
;;
;; sming.abnf -- SMIng grammar in ABNF notation (RFC 2234).
;;
;; @(#) $Id: sming.abnf,v 1.24 2001/07/20 14:13:10 strauss Exp $
;;
;; Copyright (C) The Internet Society (2001). All Rights Reserved.
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;;
;;
;; This file is WORK IN PROGRESS.
;;
smingFile = optsep *(moduleStatement optsep)
;;
;; Statement rules.
;;
moduleStatement = moduleKeyword sep ucIdentifier optsep
"{" stmtsep
*(importStatement stmtsep)
organizationStatement stmtsep
contactStatement stmtsep
descriptionStatement stmtsep
*1(referenceStatement stmtsep)
1*(revisionStatement stmtsep)
*(extensionStatement stmtsep)
*(typedefStatement stmtsep)
*(identityStatement stmtsep)
*(classStatement stmtsep)
"}" optsep ";"
extensionStatement = extensionKeyword sep lcIdentifier optsep
"{" stmtsep
statusStatement stmtsep
descriptionStatement stmtsep
*1(referenceStatement stmtsep)
*1(abnfStatement stmtsep)
"}" optsep ";"
typedefStatement = typedefKeyword sep ucIdentifier optsep
"{" stmtsep
typedefTypeStatement stmtsep
*1(defaultStatement stmtsep)
*1(formatStatement stmtsep)
*1(unitsStatement stmtsep)
statusStatement stmtsep
descriptionStatement stmtsep
*1(referenceStatement stmtsep)
"}" optsep ";"
identityStatement = identityKeyword sep lcIdentifier optsep
*1(":" optsep qlcIdentifier optsep)
"{" stmtsep
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statusStatement stmtsep
descriptionStatement stmtsep
*1(referenceStatement stmtsep)
"}" optsep ";"
classStatement = classKeyword sep ucIdentifier optsep
*1(":" optsep qucIdentifier optsep)
"{" stmtsep
*(attributeStatement stmtsep)
*1(uniqueStatement stmtsep)
*(eventStatement stmtsep)
statusStatement stmtsep
descriptionStatement stmtsep
*1(referenceStatement stmtsep)
"}" optsep ";"
attributeStatement = attributeKeyword sep
qucIdentifier sep
lcIdentifier optsep
"{" stmtsep
*1(accessStatement stmtsep)
*1(defaultStatement stmtsep)
*1(formatStatement stmtsep)
*1(unitsStatement stmtsep)
statusStatement stmtsep
descriptionStatement stmtsep
*1(referenceStatement stmtsep)
"}" optsep ";"
uniqueStatement = uniqueKeyword optsep
"(" optsep qlcIdentifierList
optsep ")" optsep ";"
eventStatement = eventKeyword sep lcIdentifier
optsep "{" stmtsep
statusStatement stmtsep
descriptionStatement stmtsep
*1(referenceStatement stmtsep)
"}" optsep ";"
importStatement = importKeyword sep ucIdentifier optsep
"(" optsep
identifierList optsep
")" optsep ";"
revisionStatement = revisionKeyword optsep "{" stmtsep
dateStatement stmtsep
descriptionStatement stmtsep
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"}" optsep ";"
typedefTypeStatement = typeKeyword sep refinedBaseType optsep ";"
dateStatement = dateKeyword sep date optsep ";"
organizationStatement = organizationKeyword sep text optsep ";"
contactStatement = contactKeyword sep text optsep ";"
formatStatement = formatKeyword sep format optsep ";"
unitsStatement = unitsKeyword sep units optsep ";"
statusStatement = statusKeyword sep status optsep ";"
accessStatement = accessKeyword sep access optsep ";"
defaultStatement = defaultKeyword sep anyValue optsep ";"
descriptionStatement = descriptionKeyword sep text optsep ";"
referenceStatement = referenceKeyword sep text optsep ";"
abnfStatement = abnfKeyword sep text optsep ";"
;;
;;
;;
refinedBaseType = IdentityKeyword /
ObjectIdentifierKeyword /
OctetStringKeyword *1(optsep numberSpec) /
PointerKeyword *1(optsep pointerSpec) /
Integer32Keyword *1(optsep numberSpec) /
Unsigned32Keyword *1(optsep numberSpec) /
Integer64Keyword *1(optsep numberSpec) /
Unsigned64Keyword *1(optsep numberSpec) /
Float32Keyword *1(optsep floatSpec) /
Float64Keyword *1(optsep floatSpec) /
Float128Keyword *1(optsep floatSpec) /
EnumerationKeyword
optsep namedSignedNumberSpec /
BitsKeyword optsep namedNumberSpec
refinedType = qucIdentifier *1(optsep anySpec)
anySpec = pointerSpec / numberSpec / floatSpec
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pointerSpec = "(" optsep qlcIdentifier optsep ")"
numberSpec = "(" optsep numberElement
*furtherNumberElement
optsep ")"
furtherNumberElement = optsep "|" optsep numberElement
numberElement = signedNumber *1numberUpperLimit
numberUpperLimit = optsep ".." optsep signedNumber
floatSpec = "(" optsep floatElement
*furtherFloatElement
optsep ")"
furtherFloatElement = optsep "|" optsep floatElement
floatElement = floatValue *1floatUpperLimit
floatUpperLimit = optsep ".." optsep floatValue
namedNumberSpec = "(" optsep namedNumberList optsep ")"
namedNumberList = namedNumberItem
*(optsep "," optsep namedNumberItem)
*1(optsep ",")
namedNumberItem = lcIdentifier optsep "(" optsep number
optsep ")"
namedSignedNumberSpec = "(" optsep namedSignedNumberList optsep ")"
namedSignedNumberList = namedSignedNumberItem
*(optsep "," optsep
namedSignedNumberItem)
*1(optsep ",")
namedSignedNumberItem = lcIdentifier optsep "(" optsep signedNumber
optsep ")"
identifierList = identifier
*(optsep "," optsep identifier)
*1(optsep ",")
qIdentifierList = qIdentifier
*(optsep "," optsep qIdentifier)
*1(optsep ",")
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qlcIdentifierList = qlcIdentifier
*(optsep "," optsep qlcIdentifier)
*1(optsep ",")
bitsValue = "(" optsep bitsList optsep ")"
bitsList = *1(lcIdentifier
*(optsep "," optsep lcIdentifier))
*1(optsep ",")
;;
;; Other basic rules.
;;
identifier = ucIdentifier / lcIdentifier
qIdentifier = qucIdentifier / qlcIdentifier
ucIdentifier = ucAlpha *63(ALPHA / DIGIT / "-")
qucIdentifier = *1(ucIdentifier "::") ucIdentifier
lcIdentifier = lcAlpha *63(ALPHA / DIGIT / "-")
qlcIdentifier = *1(ucIdentifier "::") lcIdentifier
attrIdentifier = lcIdentifier *("." lcIdentifier)
qattrIdentifier = *1(ucIdentifier ".") attrIdentifier
text = textSegment *(optsep textSegment)
textSegment = DQUOTE *textAtom DQUOTE
textAtom = textVChar / HTAB / SP / lineBreak
date = DQUOTE 4DIGIT "-" 2DIGIT "-" 2DIGIT
*1(" " 2DIGIT ":" 2DIGIT)
DQUOTE
; always in UTC
format = textSegment
units = textSegment
anyValue = bitsValue /
signedNumber /
hexadecimalNumber /
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floatValue /
text /
objectIdentifier
; Note: `objectIdentifier' includes the
; syntax of enumeration labels and
; identities.
; They are not named literally to
; avoid reduce/reduce conflicts when
; building LR parsers based on this
; grammar.
status = currentKeyword /
deprecatedKeyword /
obsoleteKeyword
access = eventonlyKeyword /
readonlyKeyword /
readwriteKeyword
objectIdentifier = (qlcIdentifier / subid "." subid)
*127("." subid)
subid = decimalNumber
number = hexadecimalNumber / decimalNumber
negativeNumber = "-" decimalNumber
signedNumber = number / negativeNumber
decimalNumber = "0" / (nonZeroDigit *DIGIT)
zeroDecimalNumber = 1*DIGIT
hexadecimalNumber = %x30 %x78 ; "0x" with x only lower-case
1*(HEXDIG HEXDIG)
floatValue = neginfKeyword /
posinfKeyword /
snanKeyword /
qnanKeyword /
signedNumber "." zeroDecimalNumber
*1("E" ("+"/"-") zeroDecimalNumber)
;;
;; Rules to skip unknown statements
;; with arbitrary arguments and blocks.
;;
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unknownStatement = unknownKeyword optsep *unknownArgument
optsep ";"
unknownArgument = ("(" optsep unknownList optsep ")") /
("{" optsep *unknownStatement optsep "}") /
qucIdentifier /
anyValue /
anySpec
unknownList = namedNumberList /
qIdentifierList
unknownKeyword = lcIdentifier
;;
;; Keyword rules.
;;
;; Typically, keywords are represented by tokens returned from the
;; lexical analyzer. Note, that the lexer has to be stateful to
;; distinguish keywords from identifiers depending on the context
;; position in the input stream.
;;
;; Also note, that these keyword definitions are represented in
;; cleartext for readability, while SMIng keywords are meant to be
;; case-sensitive, although ABNF makes quoted strings like these to
;; be case-insensitive.
;;
;; Statement keywords. They must be lower-case.
moduleKeyword = %x6D %x6F %x64 %x75 %x6C %x65
importKeyword = %x69 %x6D %x70 %x6F %x72 %x74
revisionKeyword = %x72 %x65 %x76 %x69 %x73 %x69 %x6F %x6E
dateKeyword = %x64 %x61 %x74 %x65
organizationKeyword = %x6F %x72 %x67 %x61 %x6E %x69 %x7A %x61 %x74
%x69 %x6F %x6E
contactKeyword = %x63 %x6F %x6E %x74 %x61 %x63 %x74
descriptionKeyword = %x64 %x65 %x73 %x63 %x72 %x69 %x70 %x74 %x69
%x6F %x6E
referenceKeyword = %x72 %x65 %x66 %x65 %x72 %x65 %x6E %x63 %x65
extensionKeyword = %x65 %x78 %x74 %x65 %x6E %x73 %x69 %x6F %x6E
typedefKeyword = %x74 %x79 %x70 %x65 %x64 %x65 %x66
typeKeyword = %x74 %x79 %x70 %x65
identityKeyword = %x69 %x64 %x65 %x6E %x74 %x69 %x74 %x79
classKeyword = %x63 %x6C %x61 %x73 %x73
attributeKeyword = %x61 %x74 %x74 %x72 %x69 %x62 %x75 %x74 %x65
uniqueKeyword = %x75 %x6E %x69 %x71 %x75 %x65
eventKeyword = %x65 %x76 %x65 %x6E %x74
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formatKeyword = %x66 %x6F %x72 %x6D %x61 %x74
unitsKeyword = %x75 %x6E %x69 %x74 %x73
statusKeyword = %x73 %x74 %x61 %x74 %x75 %x73
accessKeyword = %x61 %x63 %x63 %x65 %x73 %x73
defaultKeyword = %x64 %x65 %x66 %x61 %x75 %x6C %x74
abnfKeyword = %x61 %x62 %x6E %x66
;; Base type keywords.
OctetStringKeyword = %x4F %x63 %x74 %x65 %x74 %x53 %x74 %x72 %x69
%x6E %x67
PointerKeyword = %x50 %x6F %x69 %x6E %x74 %x65 %x72
IdentityKeyword = %x49 %x64 %x65 %x6E %x74 %x69 %x74 %x79
ObjectIdentifierKeyword = %x4F %x62 %x6A %x65 %x63 %x74 %x49 %x64
%x65 %x6E %x74 %x69 %x66 %x69 %x65 %x72
Integer32Keyword = %x49 %x6E %x74 %x65 %x67 %x65 %x72 %x33 %x32
Unsigned32Keyword = %x55 %x6E %x73 %x69 %x67 %x6E %x65 %x64 %x33
%x32
Integer64Keyword = %x49 %x6E %x74 %x65 %x67 %x65 %x72 %x36 %x34
Unsigned64Keyword = %x55 %x6E %x73 %x69 %x67 %x6E %x65 %x64 %x36
%x34
Float32Keyword = %x46 %x6C %x6F %x61 %x74 %x33 %x32
Float64Keyword = %x46 %x6C %x6F %x61 %x74 %x36 %x34
Float128Keyword = %x46 %x6C %x6F %x61 %x74 %x31 %x32 %x38
BitsKeyword = %x42 %x69 %x74 %x73
EnumerationKeyword = %x45 %x6E %x75 %x6D %x65 %x72 %x61 %x74 %x69
%x6F %x6E
;; Status keywords.
currentKeyword = %x63 %x75 %x72 %x72 %x65 %x6E %x74
deprecatedKeyword = %x64 %x65 %x70 %x72 %x65 %x63 %x61 %x74 %x65
%x64
obsoleteKeyword = %x6F %x62 %x73 %x6F %x6C %x65 %x74 %x65
;; Access keywords.
eventonlyKeyword = %x65 %x76 %x65 %x6E %x74 %x6F %x6E %x6C %x79
readonlyKeyword = %x72 %x65 %x61 %x64 %x6F %x6E %x6C %x79
readwriteKeyword = %x72 %x65 %x61 %x64 %x77 %x72 %x69 %x74 %x65
;; Special floating point values' keywords.
neginfKeyword = %x6E %x65 %x67 %x69 %x6E %x66
posinfKeyword = %x70 %x6F %x73 %x69 %x6E %x66
snanKeyword = %x73 %x6E %x61 %x6E
qnanKeyword = %x71 %x6E %x61 %x6E
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;;
;; Some low level rules.
;; These tokens are typically skipped by the lexical analyzer.
;;
sep = 1*(comment / lineBreak / WSP)
; unconditional separator
optsep = *(comment / lineBreak / WSP)
stmtsep = *(comment /
lineBreak /
WSP /
unknownStatement)
comment = "//" *(WSP / VCHAR) lineBreak
lineBreak = CRLF / LF
;;
;; Encoding specific rules.
;;
textVChar = %x21 / %x23-7E
; any VCHAR except DQUOTE
ucAlpha = %x41-5A
lcAlpha = %x61-7A
nonZeroDigit = %x31-39
;;
;; RFC 2234 core rules.
;;
ALPHA = %x41-5A / %x61-7A
; A-Z / a-z
CR = %x0D
; carriage return
CRLF = CR LF
; Internet standard newline
DIGIT = %x30-39
; 0-9
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DQUOTE = %x22
; " (Double Quote)
HEXDIG = DIGIT /
%x61 / %x62 / %x63 / %x63 / %x65 / %x66
; only lower-case a..f
HTAB = %x09
; horizontal tab
LF = %x0A
; linefeed
SP = %x20
; space
VCHAR = %x21-7E
; visible (printing) characters
WSP = SP / HTAB
; white space
;;
;; EOF
;;
Appendix B. OPEN ISSUES
Set of Documents - What is the expected set of documents specifying
the SMIng? Currently, it looks like we are going to define these:
(a) a core SMIng language specification,
(b) specification of a core SMIng module,
(c) language extensions for SNMP mappings,
(d) language extensions for COPS-PR mappings,
(e) maybe, an SMIng guidelines document,
(f) specification of a basic inet modules, that not
only contain basic definitions but also document
the usage SMIng.
How Generic Shall the Core Language be? - If we focus strictly on
SNMP and COPS-PR, we can build on some common characteristics in
these two related worlds, e.g., the concept and common definitions
of OIDs, and conformance statements. On the other hand, if we
feel closer to OO modeling concepts that should remain applicable
also to other environments (AAA/DIAMETER, XML-style definitions),
more information has to be specified in the mappings to those
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environments, while the core language cannot be very expressive.
Floating Point Types - Shall we include Float32/64/128 in the base
type system? Maybe only Float32/64? If we do, shall we disallow
restrictions? See also the requirements document.
Events / NOTIFICATIONs - SMIv2 NOTIFICATIONs contain objects. How
about SMIng? Assume, the clause is named `event'. Shall events
carry a set of attributes? How about those attributes identifying
an instance of a class? Currently, events are assiciated with a
class. What atttributes are carried with an event is subject to
the protocol mapping.
Display Formats - Should display hints be usable in a reversed way?
Check all variants carefully. Is the optional repeat indicator
`*' necessary? Would `u' for unsigned integers be useful?
Discriminated Unions - How to specify unions and their
discriminators? `typemap' statement? What are the specific
requirements? See also the requirements document.
How To Read - Add a section on how to read this set of documents.
Annotations - Make annotations a core feature of SMIng? They are
used to add information to an existent definition in an external
module, e.g., a vendor or user can add specific severity level
information to standard event definitions.
Glossary - Add/Update the glossary of terms.
Module Naming Scheme - Propose well known module name suffixes: `-
MIB' for SNMP mapping modules? `-PIB' for COPS-PR mapping modules?
`-EXT' for modules that define extensions (e.g. snmp)? no
extension for modules that define general classes and types? This
should go to the Guidelines document.
`Extending A Module' - Carefully adjust the rules, e.g., `new named
numbers may be added to enumeration types' is in contradiction
with `attributes may get a new type only if the set of values
remains equal'.
ABNF Statement - Is the `abnf' statement really meaningful? Someone
stated that it could be abused.
7-bit ASCII texts - See requirements.
Module Namespaces - Should we introduce domain-based namespaces for
module names? E.g., DISMAN-SCRIPT-MIB.ietf.org? Mapping to
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SMIv2/SPPI module names? Which parts are case-sensitive? Separator
char between module name and domain name (@/.)? Or should we
enforce organization prefixes (also for the IETF), like IETF-
DISMAN-SCRIPT-MIB?
Learn from ODL, XML, ODBMS - Look at the ODL proposal from TINAC.
Look at the XML schema work from W3C. Look at the ODBMS work.
Inheritence - Inheritence is a powerful technique in software
development. But is it really what we want to have in management
data modeling? If it is not easy to find good examples for
inheritence, can we expect that people will know how to use it? Or
would it be more likely that it will be misused? Maybe,
containment/discriminated unions are what we really need.
Examples for Primary goals: MIBs/PIBs - Keep in mind that the
primary goal is to derive modules for use with SNMP and COPS-PR
from common definitions. If we cannot easily give good examples,
we have failed.
Classes or Interfaces - Are classes really classes or are they more
interfaces?
Reusable event definitions - Currently events are defined within a
class. Do we need to be able to reuse event definitions in
multiple classes? This potentially requires to give events their
own names, independent of any class definitions. Or is it
sufficient to use inheritance/containment to handle 99 % of the
cases?
Extensions - Optionally require the understanding of imported
extensions (similar to the marvelous diameter M bit ;-)
Extension Context - Do we need a mechanism to allow an extension to
specify the context in which it can be used (the containing
statement block in the position within this block)?
`Static' Definitions - Is it useful to make specific definitions
non-exported (like `static' in C)? Or would it be useful to make
only those definitions be exported that are explicitly marked
(`public')?
More Formal Restrictions? - Do we need further formal restrictions
on type definitions, e.g. subtyping not allowed on TimeTicks,
max-access read-only on Counters, no default values on Counters?
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Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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