Semantic Definition Format (SDF) for Data and Interactions of Things
draft-ietf-asdf-sdf-01
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| Last updated | 2020-11-15 (Latest revision 2020-11-14) | ||
| Replaces | draft-onedm-t2trg-sdf | ||
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draft-ietf-asdf-sdf-01
T2TRG M. Koster, Ed.
Internet-Draft SmartThings
Intended status: Informational C. Bormann, Ed.
Expires: 19 May 2021 Universität Bremen TZI
15 November 2020
Semantic Definition Format (SDF) for Data and Interactions of Things
draft-ietf-asdf-sdf-01
Abstract
The Semantic Definition Format (SDF) is a format for domain experts
to use in the creation and maintenance of data and interaction models
in the Internet of Things. It was created as a common language for
use in the development of the One Data Model liaison organization
(OneDM) definitions. Tools convert this format to database formats
and other serializations as needed.
An SDF specification describes definitions of SDF Objects and their
associated interactions (Events, Actions, Properties), as well as the
Data types for the information exchanged in those interactions.
A JSON format representation of SDF 1.0 was defined in the previous
(-00) version of this document. SDF 1.1 is expected to be defined in
a future version; the present document represents a draft on the way
from 1.0 to 1.1. Hence, this is not an implementation draft.
Contributing
Recent versions of this document are available at its GitHub
repository https://github.com/ietf-wg-asdf/SDF (https://github.com/
ietf-wg-asdf/SDF) -- this also provides an issue tracker as well as a
way to supply "pull requests".
General discussion of this SDF Internet-Draft happens on the mailing
list of the IETF ASDF Working Group, asdf@ietf.org (subscribe at
https://www.ietf.org/mailman/listinfo/asdf
(https://www.ietf.org/mailman/listinfo/asdf)).
The IETF Note Well applies (https://www.ietf.org/about/note-well/
(https://www.ietf.org/about/note-well/)).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology and Conventions . . . . . . . . . . . . . . . 3
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Example Definition . . . . . . . . . . . . . . . . . . . 5
2.2. Elements of an SDF model . . . . . . . . . . . . . . . . 7
2.2.1. sdfObject . . . . . . . . . . . . . . . . . . . . . . 8
2.2.2. sdfProperty . . . . . . . . . . . . . . . . . . . . . 8
2.2.3. sdfAction . . . . . . . . . . . . . . . . . . . . . . 9
2.2.4. sdfEvent . . . . . . . . . . . . . . . . . . . . . . 10
2.2.5. sdfData . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.6. sdfThing . . . . . . . . . . . . . . . . . . . . . . 11
2.2.7. sdfProduct . . . . . . . . . . . . . . . . . . . . . 11
3. SDF structure . . . . . . . . . . . . . . . . . . . . . . . . 11
3.1. Information block . . . . . . . . . . . . . . . . . . . . 11
3.2. Namespaces section . . . . . . . . . . . . . . . . . . . 12
3.3. Definitions section . . . . . . . . . . . . . . . . . . . 13
4. Names and namespaces . . . . . . . . . . . . . . . . . . . . 14
4.1. Structure . . . . . . . . . . . . . . . . . . . . . . . . 14
4.2. Contributing global names . . . . . . . . . . . . . . . . 15
4.3. Referencing global names . . . . . . . . . . . . . . . . 15
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4.4. sdfRef . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.5. sdfRequired . . . . . . . . . . . . . . . . . . . . . . . 17
4.5.1. Optionality using the keyword "sdfRequired" . . . . . 17
4.6. Common Qualities . . . . . . . . . . . . . . . . . . . . 18
4.7. Data Qualities . . . . . . . . . . . . . . . . . . . . . 19
5. Keywords for definition groups . . . . . . . . . . . . . . . 23
5.1. sdfObject . . . . . . . . . . . . . . . . . . . . . . . . 23
5.2. sdfProperty . . . . . . . . . . . . . . . . . . . . . . . 23
5.3. sdfAction . . . . . . . . . . . . . . . . . . . . . . . . 24
5.4. sdfEvent . . . . . . . . . . . . . . . . . . . . . . . . 24
5.5. sdfData . . . . . . . . . . . . . . . . . . . . . . . . . 25
6. High Level Composition . . . . . . . . . . . . . . . . . . . 25
6.1. Paths in the model namespaces . . . . . . . . . . . . . . 26
6.2. Modular Composition . . . . . . . . . . . . . . . . . . . 26
6.2.1. Use of the "sdfRef" keyword to re-use a definition . 26
6.3. sdfThing . . . . . . . . . . . . . . . . . . . . . . . . 27
6.4. sdfProduct . . . . . . . . . . . . . . . . . . . . . . . 28
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.1. Normative References . . . . . . . . . . . . . . . . . . 28
7.2. Informative References . . . . . . . . . . . . . . . . . 29
Appendix A. Formal Syntax of SDF . . . . . . . . . . . . . . . . 30
Appendix B. json-schema.org Rendition of SDF Syntax . . . . . . 33
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 34
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34
1. Introduction
The Semantic Definition Format (SDF) is a format for domain experts
to use in the creation and maintenance of data and interaction models
in the Internet of Things. It was created as a common language for
use in the development of the One Data Model liaison organization
(OneDM) definitions. Tools convert this format to database formats
and other serializations as needed.
An SDF specification describes definitions of SDF Objects and their
associated interactions (Events, Actions, Properties), as well as the
Data types for the information exchanged in those interactions.
A JSON format representation of SDF 1.0 was defined in the previous
(-00) version of this document. SDF 1.1 is expected to be defined in
a future version; the present document represents a draft on the way
from 1.0 to 1.1. Hence, this is not an implementation draft.
1.1. Terminology and Conventions
Thing: A physical device that is also made available in the Internet
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of Things. The term is used here for Things that are notable for
their interaction with the physical world beyond interaction with
humans; a temperature sensor or a light might be a Thing, but a
router that employs both temperature sensors and indicator lights
might exhibit less Thingness, as the effects of its functioning
are mostly on the digital side.
Affordance: An element of an interface offered for interaction,
defining its possible uses or making clear how it can or should be
used. The term is used here for the digital interfaces of a Thing
only; it might also have physical affordances such as buttons,
dials, and displays.
Quality: A metadata item in a definition or declaration which says
something about that definition or declaration. A quality is
represented in SDF as an entry in a JSON map (object) that serves
as a definition or declaration.
Entry: A key-value pair in a map. (In JSON maps, sometimes also
called "member".)
Block: One or more entries in a JSON map that is part of an SDF
specification; these entries together serve a specific function.
Group: An entry in the main SDF map and in certain nested
definitions that has a Class Name Keyword as its key and a map of
definition entries (Definition Group) as a value.
Class Name Keyword: One of sdfThing, sdfProduct, sdfObject,
sdfProperty, sdfAction, sdfEvent, or sdfData; the Classes for
these type keywords are capitalized and prefixed with "sdf".
Class: Abstract term for the information that is contained in groups
identified by a Class Name Keyword.
Property: An affordance that can potentially be used to read, write,
and/or observe state on an Object. (Note that Entries are often
called properties in other environments; in this document, the
term Property is specifically reserved for affordances, even if
the map key "properties" might be imported from a data definition
language with the other semantics.)
Action: An affordance that can potentially be used to perform a
named operation on an Object.
Event: An affordance that can potentially be used to obtain
information about what happened to an Object.
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Object: A grouping of Property, Action, and Event definitions; the
main "atom" of reusable semantics for model construction. (Note
that JSON maps are often called JSON objects due to JSON's
JavaScript heritage; in this document, the term Object is
specifically reserved for the above grouping, even if the type
name "object" might be imported from a data definition language
with the other semantics.)
Element: A part or an aspect of something abstract; used here in its
usual English definition. (Occasionally, also used specifically
for the elements of JSON arrays.)
Definition: An entry in a Definition Group; the entry creates a new
semantic term for use in SDF models and associates it with a set
of qualities.
Declaration: A reference to and a use of a definition within an
enclosing definition, intended to create component instances
within that enclosing definition. Every declaration can also be
used as a definition for reference in a different place.
Protocol Binding: A companion document to an SDF specification that
defines how to map the abstract concepts in the specification into
the protocols in use in a specific ecosystem. Might supply URL
components, numeric IDs, and similar details.
Conventions:
* The singular form is chosen as the preferred one for the keywords
defined here.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Overview
2.1. Example Definition
We start with an example for the SDF definition of a simple Object
called "Switch" (Figure 1).
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{
"info": {
"title": "Example file for OneDM Semantic Definition Format",
"version": "2019-04-24",
"copyright": "Copyright 2019 Example Corp. All rights reserved.",
"license": "https://example.com/license"
},
"namespace": {
"cap": "https://example.com/capability/cap"
},
"defaultNamespace": "cap",
"sdfObject": {
"Switch": {
"sdfProperty": {
"value": {
"description": "The state of the switch; false for off and true for on."
"type": "boolean"
}
},
"sdfAction": {
"on": {
"description": "Turn the switch on; equivalent to setting value to true."
},
"off": {
"description": "Turn the switch off; equivalent to setting value to false."
},
"toggle": {
"description": "Toggle the switch; equivalent to setting value to its complement."
}
}
}
}
}
Figure 1: A simple example of an SDF definition file
This is a model of a switch. The state "value" declared in the
"sdfProperty" group, represented by a Boolean, will be true for "on"
and will be false for "off". The actions "on" or "off" declared in
the "sdfAction" group are redundant with setting the "value" and are
in the example to illustrate that there are often different ways of
achieving the same effect. The action "toggle" will invert the value
of the sdfProperty value, so that 2-way switches can be created;
having such action will avoid the need for first retrieving the
current value and then applying/setting the inverted value.
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The "sdfObject" group lists the affordances of instances of this
object. The "sdfProperty" group lists the property affordances
described by the model; these represent various perspectives on the
state of the object. Properties can have additional qualities to
describe the state more precisely. Properties can be annotated to be
read, write or read/write; how this is actually done by the
underlying transfer protocols is not described in the SDF model but
left to companion protocol bindings. Properties are often used with
RESTful paradigms [I-D.irtf-t2trg-rest-iot], describing state. The
"sdfAction" group is the mechanism to describe other interactions in
terms of their names, input, and output data (no data are used in the
example), as in a POST method in REST or in a remote procedure call.
The example "toggle" is an Action that changes the state based on the
current state of the Property named "value". (The third type of
affordance is Events, which are not described in this example.)
2.2. Elements of an SDF model
The SDF language uses seven predefined Class Name Keywords for
modeling connected Things, six of which are illustrated in Figure 2
(the seventh class "sdfProduct" is exactly like "sdfThing").
,--------.
|sdfThing|
|--------|
|--------|
`--------'
|
|
,---------.
|sdfObject|
|---------|
|---------|
`---------'
|
,-----------. ,---------. ,--------.
|sdfProperty| |sdfAction| |sdfEvent|
|-----------| |---------| |--------|
|-----------| |---------| |--------|
`-----------' `---------' `--------'
,-------.
|sdfData|
|-------|
|-------|
`-------'
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Figure 2: Main classes used in SDF models
The seven main Class Name Keywords are discussed below.
2.2.1. sdfObject
Objects, the items listed in an "sdfObject" group, are the main
"atom" of reusable semantics for model construction. It aligns in
scope with common definition items from many IoT modeling systems,
for example ZigBee Clusters [ZCL], OMA SpecWorks LwM2M Objects [OMA],
and OCF Resource Types [OCF].
An "sdfObject" contains a set of "sdfProperty", "sdfAction", and
"sdfEvent" definitions that describe the interaction affordances
associated with some scope of functionality.
For the granularity of definition, "sdfObject" definitions are meant
to be kept narrow enough in scope to enable broad reuse and
interoperability. For example, defining a light bulb using separate
"sdfObject" definitions for on/off control, dimming, and color
control affordances will enable interoperable functionality to be
configured for diverse product types. An "sdfObject" definition for
a common on/off control may be used to control may different kinds of
Things that require on/off control.
2.2.2. sdfProperty
"sdfProperty" is used to model elements of state within "sdfObject"
instances.
An instance of "sdfProperty" may be associated with some protocol
affordance to enable the application to obtain the state variable
and, optionally, modify the state variable. Additionally, some
protocols provide for in-time reporting of state changes. (These
three aspects are described by the qualities "readable", "writable",
and "observable" defined for an "sdfProperty".)
Definitions in "sdfProperty" groups look like definitions in
"sdfData" groups, however, they actually also declare a Property with
the given qualities to be potentially present in the containing
Object. (Qualities beyond those of "sdfData" definitions could be
defined for "sdfProperty" declarations but currently aren't; this
means that even Property qualities such as "readable" and "writable"
can be associated with definitions in "sdfData" groups, as well.)
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For definitions in "sdfProperty" and "sdfData", SDF provides
qualities that can constrain the structure and values of data allowed
in an instance of these data, as well as qualities that associate
semantics to these data, for engineering units and unit scaling
information.
For the data definition within "sdfProperty" or "sdfData", SDF
borrows a number of elements proposed for the drafts 4 and 7 of the
json-schema.org "JSON Schema" format
[I-D.handrews-json-schema-validation], enhanced by qualities that are
specific to SDF. For the current version of SDF, data are
constrained to be of simple types (number, string, Boolean), JSON
maps composed of named data ("objects"), and arrays of these types.
Syntax extension points are provided that can be used to provide
richer types in future versions of this specification (possibly more
of which can be borrowed from json-schema.org).
Note that "sdfProperty" definitions (and "sdfData" definitions in
general) are not intended to constrain the formats of data used for
communication over network interfaces. Where needed, data
definitions for payloads of protocol messages are expected to be part
of the protocol binding.
2.2.3. sdfAction
The "sdfAction" group contains declarations of Actions, model
affordances that, when triggered, have more effect than just reading,
updating, or observing Thing state, often resulting in some outward
physical effect (which, itself, cannot be modeled in SDF). From a
programmer's perspective, they might be considered to be roughly
analogous to method calls.
Actions may have data parameters; these are modeled as a single item
of input data and output data, each. (Where multiple parameters need
to be modeled, an "object" type can be used to combine these
parameters into one.) Actions may be long-running, that is to say
that the effects may not take place immediately as would be expected
for an update to an "sdfPoperty"; the effects may play out over time
and emit action results. Actions may also not always complete and
may result in application errors, such as an item blocking the
closing of an automatic door.
Actions may have (or lack) qualities of idempotency and side-effect
safety.
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The current version of SDF only provides data constraint modeling and
semantics for the input and output data of definitions in "sdfAction"
groups. Again, data definitions for payloads of protocol messages,
and detailed protocol settings for invoking the action, are expected
to be part of the protocol binding.
2.2.4. sdfEvent
The "sdfEvent" group contains declarations of Events, which can model
affordances that inform about "happenings" associated with an
instance of an Object; these may result in a signal being stored or
emitted as a result.
Note that there is a trivial overlap with sdfProperty state changes,
which may also be defined as events but are not generally required to
be defined as such. However, Events may exhibit certain ordering,
consistency, and reliability requirements that are expected to be
supported in various implementations of "sdfEvent" that do
distinguish sdfEvent from sdfProperty. For instance, while a state
change may simply be superseded by another state change, some events
are "precious" and need to be preserved even if further events
follow.
The current version of SDF only provides data constraint modeling and
semantics for the output data of Event affordances. Again, data
definitions for payloads of protocol messages, and detailed protocol
settings for invoking the action, are expected to be part of the
protocol binding.
2.2.5. sdfData
Definitions in "sdfData" groups are provided separately from those in
"sdfProperty" groups to enable common modeling patterns, data
constraints, and semantic anchor concepts to be factored out for data
items that make up "sdfProperty" items and serve as input and output
data for "sdfAction" and "sdfEvent" items.
It is a common use case for such a data definition to be shared
between an "sdfProperty" item and input or output parameters of an
"sdfAction" or output data provided by an "sdfEvent". "sdfData"
definitions also enable factoring out extended application data types
such as mode and machine state enumerations to be reused across
multiple definitions that have similar basic characteristics and
requirements.
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2.2.6. sdfThing
Back at the top level, the "sdfThing" groups enables definition of
models for complex devices that will use one or more "sdfObject"
definitions.
A definition in an "sdfThing" group can refine the metadata of the
definitions it is composed from: other definitions in "sdfThing"
groups definitions in "sdfObject" groups.
2.2.7. sdfProduct
"sdfThing" has a derived class "sdfProduct", which can be used to
indicate a top level inventory item with a Stock-Keeping Unit (SKU)
identifier and other particular metadata. Structurally, there is no
difference between definitions in either group; semantically, a
definition in an "sdfProduct" group is intended to describe a class
of complete Things.
3. SDF structure
SDF definitions are contained in SDF files. One or more SDF files
can work together to provide the definitions and declarations that
are the payload of the SDF format.
A SDF definition file contains a single JSON map (JSON object). This
object has three sections: the information block, the namespaces
section, and the definitions section.
3.1. Information block
The information block contains generic meta data for the file itself
and all included definitions.
The keyword (map key) that defines an information block is "info".
Its value is a JSON map in turn, with a set of entries that represent
qualities that apply to the included definition.
Qualities of the information block are shown in Table 1.
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+===========+========+==========+=================================+
| Quality | Type | Required | Description |
+===========+========+==========+=================================+
| title | string | yes | A short summary to be displayed |
| | | | in search results, etc. |
+-----------+--------+----------+---------------------------------+
| version | string | yes | The incremental version of the |
| | | | definition, format TBD |
+-----------+--------+----------+---------------------------------+
| copyright | string | yes | Link to text or embedded text |
| | | | containing a copyright notice |
+-----------+--------+----------+---------------------------------+
| license | string | yes | Link to text or embedded text |
| | | | containing license terms |
+-----------+--------+----------+---------------------------------+
Table 1: Qualities of the Information Block
While the format of the version string is marked as TBD, it is
intended to be lexicographically increasing over the life of a model:
a newer model always has a version string that string-compares higher
than all previous versions. This is easily achieved by following the
convention to start the version with an [RFC3339] "date-time" or, if
new versions are generated less frequently than once a day, just the
"full-date" (i.e., YYYY-MM-DD); in many cases, that will be all that
is needed (see Figure 1 for an example).
The license string is preferably either a URI that points to a web
page with an unambiguous definition of the license, or an [SPDX]
license identifier. (For models to be handled by the One Data Model
liaison group, this will typically be "BSD-3-Clause".)
3.2. Namespaces section
The namespaces section contains the namespace map and the
defaultNamespace setting.
The namespace map is a map from short names for URIs to the namespace
URIs themselves.
The defaultNamespace setting selects one of the entries in the
namespace map by giving its short name. The associated URI (value of
this entry) becomes the default namespace for the SDF definition
file.
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+==================+========+==========+=======================+
| Quality | Type | Required | Description |
+==================+========+==========+=======================+
| namespace | map | no | Defines short names |
| | | | mapped to namespace |
| | | | URIs, to be used as |
| | | | identifier prefixes |
+------------------+--------+----------+-----------------------+
| defaultNamespace | string | no | Identifies one of the |
| | | | prefixes in the |
| | | | namespace map to be |
| | | | used as a default in |
| | | | resolving identifiers |
+------------------+--------+----------+-----------------------+
Table 2: Namespaces Section
The following example declares a set of namespaces and defines "cap"
as the default namespace. By convention, the values in the namespace
map contain full URIs without a fragment identifier, and the fragment
identifier is then added, if needed, where the namespace entry is
used.
"namespace": {
"cap": "https://example.com/capability/cap",
"zcl": "https://zcl.example.com/sdf"
},
"defaultNamespace": "cap",
If no defaultNamespace setting is given, the SDF definition file does
not contribute to a global namespace. As the defaultNamespace is set
by giving a namespace short name, its presence requires a namespace
map that contains a mapping for that namespace short name.
If no namespace map is given, no short names for namespace URIs are
set up, and no defaultNamespace can be given.
3.3. Definitions section
The Definitions section contains one or more groups, each identified
by a Class Name Keyword (there can only be one group per keyword; the
actual grouping is just a shortcut and does not carry any specific
semantics). The value of each group is a JSON map (object), the keys
of which serve for naming the individual definitions in this group,
and the corresponding values provide a set of qualities (name-value
pairs) for the individual definition. (In short, we speak of the map
entries as "named sets of qualities".)
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Each group may contain zero or more definitions. Each identifier
defined creates a new type and term in the target namespace.
Declarations have a scope of the current definition block.
A definition may in turn contain other definitions. Each definition
is a named set of qualities, i.e., it consists of the newly defined
identifier and a set of key-value pairs that represent the defined
qualities and contained definitions.
An example for an Object definition is given in Figure 3:
"sdfObject": {
"foo": {
"sdfProperty": {
"bar": {
"type": "boolean"
}
}
}
}
Figure 3: Example Object definition
This example defines an Object "foo" that is defined in the default
namespace (full address: "#/sdfObject/foo"), containing a property
that can be addressed as "#/sdfObject/foo/sdfProperty/bar", with data
of type boolean.
Some of the definitions are also declarations: the definition of the
entry "bar" in the property "foo" means that each instance of a "foo"
can have zero or one instance of a "bar". Entries within
"sdfProperty", "sdfAction", and "sdfEvent", within "sdfObject"
entries, are declarations. Similarly, entries within an "sdfThing"
describe instances of "sdfObject" (or nested "sdfThing") that form
part of instances of the Thing.
4. Names and namespaces
SDF definition files may contribute to a global namespace, and may
reference elements from that global namespace. (An SDF definition
file that does not set a defaultNamespace does not contribute to a
global namespace.)
4.1. Structure
Global names look exactly like "https://" URIs with attached fragment
identifiers.
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There is no intention to require that these URIs can be dereferenced.
(However, as future versions of SDF might find a use for
dereferencing global names, the URI should be chosen in such a way
that this may become possible in the future.)
The absolute URI of a global name should be a URI as per Section 3 of
[RFC3986], with a scheme of "https" and a path ("hier-part" in
[RFC3986]). For the present version of this specification, the query
part should not be used (it might be used in later versions).
The fragment identifier is constructed as per Section 6 of [RFC6901].
4.2. Contributing global names
The fragment identifier part of a global name defined in an SDF
definition file is constructed from a JSON pointer that selects the
element defined for this name in the SDF definition file.
The absolute URI part is a copy of the default namespace, i.e., the
default namespace is always the target namespace for a name for which
a definition is contributed. When emphasizing that name definitions
are contributed to the default namespace, we therefore also call it
the "target namespace" of the SDF definition file.
E.g., in Figure 1, definitions for the following global names are
contributed:
* https://example.com/capability/cap#/sdfObject/Switch
* https://example.com/capability/cap#/sdfObject/Switch/sdfProperty/
value
* https://example.com/capability/cap#/sdfObject/Switch/sdfAction/on
* https://example.com/capability/cap#/sdfObject/Switch/sdfAction/off
Note the "#", which separates the absolute-URI part (Section 4.3 of
[RFC3986]) from the fragment identifier part.
4.3. Referencing global names
A name reference takes the form of the production "curie" in
[W3C.NOTE-curie-20101216] (note that this excludes the production
"safe-curie"), but also limiting the IRIs involved in that production
to URIs as per [RFC3986] and the prefixes to ASCII characters
[RFC0020].
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A name that is contributed by the current SDF definition file can be
referenced by a Same-Document Reference as per section 4.4 of
[RFC3986]. As there is little point in referencing the entire SDF
definition file, this will be a "#" followed by a JSON pointer. This
is the only kind of name reference to itself that is possible in an
SDF definition file that does not set a default namespace.
Name references that point outside the current SDF definition file
need to contain curie prefixes. These then reference namespace
declarations in the namespaces section.
For example, if a namespace prefix is defined:
"namespace": {
"foo": "https://example.com/"
}
Then this reference to that namespace:
{ "sdfRef": "foo:#/sdfData/temperatureData" }
references the global name:
"https://example.com/#/sdfData/temperatureData"
Note that there is no way to provide a URI scheme name in a curie, so
all references outside of the document need to go through the
namespace map.
Name references occur only in specific elements of the syntax of SDF:
* copying elements via sdfRef values
* pointing to elements via sdfRequired value elements
4.4. sdfRef
In a JSON map establishing a definition, the keyword "sdfRef" is used
to copy all of the qualities of the referenced definition, indicated
by the included name reference, into the newly formed definition.
(This can be compared to the processing of the "$ref" keyword in
[I-D.handrews-json-schema-validation].)
For example, this reference:
"temperatureProperty": {
"sdfRef": "#/sdfData/temperatureData"
}
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creates a new definition "temperatureProperty" that contains all of
the qualities defined in the definition at /sdfData/temperatureData.
4.5. sdfRequired
The value of "sdfRequired" is an array of name references, each
pointing to one declaration the instantiation of which is declared
mandatory.
4.5.1. Optionality using the keyword "sdfRequired"
The keyword "sdfRequired" is provided to apply a constraint that
defines for which declarations corresponding data are mandatory in an
instance conforming the current definition.
The value of "sdfRequired" is an array of JSON pointers, each
indicating one declaration that is mandatory to be represented.
The example in Figure 4 shows two required elements in the sdfObject
definition for "temperatureWithAlarm", the sdfProperty
"temperatureData", and the sdfEvent "overTemperatureEvent". The
example also shows the use of JSON pointer with "sdfRef" to use a
pre-existing definition in this definition, for the "alarmType" data
(sdfOutputData) produced by the sdfEvent "overTemperatureEvent".
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{
"sdfObject": {
"temperatureWithAlarm": {
"sdfRequired": [
"#/sdfObject/temperatureWithAlarm/sdfData/temperatureData",
"#/sdfObject/temperatureWithAlarm/sdfEvent/overTemperatureEvent"
],
"sdfData":{
"temperatureData": {
"type": "number"
}
},
"sdfEvent": {
"overTemperatureEvent": {
"sdfOutputData": {
"type": "object",
"properties": {
"alarmType": {
"sdfRef": "cap:/sdfData/alarmTypes/quantityAlarms",
"const": "OverTemperatureAlarm"
},
"temperature": {
"sdfRef": "#/sdfObject/temperatureWithAlarm/sdfData/temperatureData"
}
}
}
}
}
}
}
}
Figure 4: Using sdfRequired
4.6. Common Qualities
Definitions in SDF share a number of qualities that provide metadata
for them. These are listed in Table 3. None of these qualities are
required or have default values that are assumed if the quality is
absent. If a label is required for an application and no label is
given in the SDF model, the last part ("reference-token", Section 3
of [RFC6901]) of the JSON pointer to the definition can be used.
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+=============+==============+===================================+
| Quality | Type | Description |
+=============+==============+===================================+
| description | text | long text (no constraints) |
+-------------+--------------+-----------------------------------+
| label | text | short text (no constraints) |
+-------------+--------------+-----------------------------------+
| $comment | text | source code comments only, no |
| | | semantics |
+-------------+--------------+-----------------------------------+
| sdfRef | sdf-pointer | (see Section 4.4) |
+-------------+--------------+-----------------------------------+
| sdfRequired | pointer-list | (see Section 4.5, applies to |
| | | qualities of properties, of data) |
+-------------+--------------+-----------------------------------+
Table 3: Common Qualities
4.7. Data Qualities
Data qualities are used in "sdfData" and "sdfProperty" definitions,
which are named sets of data qualities (abbreviated as "named-sdq").
Table 4 lists data qualities borrowed from
[I-D.handrews-json-schema-validation]; the intention is that these
qualities retain their semantics from the versions of the json-
schema.org proposal they were imported from. A description that
starts with a parenthesized term means the quality is only applicable
when "type" has the value of the term.
Table 5 lists data qualities defined specifically for the present
specification.
The term "allowed types" stands for primitive JSON types, JSON maps
("objects")" as well as homogeneous arrays of numbers, text,
Booleans, or maps. (This list might be extended in a future version
of SDF.) An "allowed value" is a value allowed for one of these
types.
+================+==========+=======================================+
|Quality |Type |Description |
+================+==========+=======================================+
|type |"number" /|JSON data type (note 1) |
| |"string" /| |
| |"boolean" | |
| |/ | |
| |"integer" | |
| |/ "array" | |
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| |/ "object"| |
+----------------+----------+---------------------------------------+
|enum |array of |enumeration constraint |
| |allowed | |
| |values | |
+----------------+----------+---------------------------------------+
|const |allowed |specifies a constant value for a data |
| |value |item or property |
+----------------+----------+---------------------------------------+
|default |allowed |specifies the default value for |
| |value |initialization |
+----------------+----------+---------------------------------------+
|minimum |number |(number) lower limit of value |
+----------------+----------+---------------------------------------+
|maximum |number |(number) upper limit of value |
+----------------+----------+---------------------------------------+
|exclusiveMinimum|number or |(number) lower limit of value |
| |boolean | |
| |(jso draft| |
| |7/4) | |
+----------------+----------+---------------------------------------+
|exclusiveMaximum|number or |(number) lower limit of value |
| |boolean | |
| |(jso draft| |
| |7/4) | |
+----------------+----------+---------------------------------------+
|multipleOf |number |(number) resolution of the number |
| | |[NEEDED?] |
+----------------+----------+---------------------------------------+
|minLength |integer |(string) shortest length string in |
| | |octets |
+----------------+----------+---------------------------------------+
|maxLength |integer |(string) longest length string in |
| | |octets |
+----------------+----------+---------------------------------------+
|pattern |string |(string) regular expression to |
| | |constrain a string pattern |
+----------------+----------+---------------------------------------+
|format |"date- |(string) JSON Schema formats as per |
| |time" / |[I-D.handrews-json-schema-validation], |
| |"date" / |Section 7.3 |
| |"time" / | |
| |"uri" / | |
| |"uri- | |
| |reference"| |
| |/ "uuid" | |
+----------------+----------+---------------------------------------+
|minItems |number |(array) Minimum number of items in |
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| | |array |
+----------------+----------+---------------------------------------+
|maxItems |number |(array) Maximum number of items in |
| | |array |
+----------------+----------+---------------------------------------+
|uniqueItems |boolean |(array) if true, requires items to be |
| | |all different |
+----------------+----------+---------------------------------------+
|items |(subset of|(array) constraints on array items |
| |common/ | |
| |data | |
| |qualities;| |
| |see | |
| |Appendix A| |
+----------------+----------+---------------------------------------+
|required |array of |(object) names of properties (note 2) |
| |strings |that are required in the JSON map |
| | |("object") |
+----------------+----------+---------------------------------------+
|properties |named set |(object) entries allowed for the JSON |
| |of data |map ("object") |
| |qualities | |
+----------------+----------+---------------------------------------+
Table 4: Qualities of sdfProperty and sdfData borrowed from json-
schema.org
(1) A type value of "integer" means that only integral values of JSON
numbers can be used.
(2) Note that the term "properties" as used for map entries in
[I-D.handrews-json-schema-validation] is unrelated to sdfProperty.
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+===============+===============+====================+=========+
| Quality | Type | Description | Default |
+===============+===============+====================+=========+
| (common) | | Section 4.6 | |
+---------------+---------------+--------------------+---------+
| unit | string | SenML unit name as | N/A |
| | | per [IANA.senml], | |
| | | subregistry SenML | |
| | | Units (note 3) | |
+---------------+---------------+--------------------+---------+
| scaleMinimum | number | lower limit of | N/A |
| | | value in units | |
| | | given by unit | |
+---------------+---------------+--------------------+---------+
| scaleMaximum | number | upper limit of | N/A |
| | | value in units | |
| | | given by unit | |
+---------------+---------------+--------------------+---------+
| readable | boolean | Reads are allowed | true |
+---------------+---------------+--------------------+---------+
| writable | boolean | Writes are allowed | true |
+---------------+---------------+--------------------+---------+
| observable | boolean | flag to indicate | true |
| | | asynchronous | |
| | | notification is | |
| | | available | |
+---------------+---------------+--------------------+---------+
| nullable | boolean | indicates a null | true |
| | | value is available | |
| | | for this type | |
+---------------+---------------+--------------------+---------+
| contentFormat | string | content type (IANA | N/A |
| | | media type string | |
| | | plus parameters), | |
| | | encoding | |
+---------------+---------------+--------------------+---------+
| subtype | "byte-string" | subtype | N/A |
| | / "unix-time" | enumeration | |
+---------------+---------------+--------------------+---------+
Table 5: SDF-defined Qualities of sdfProperty and sdfData
(3) note that the quality "unit" was called "units" in SDF 1.0.
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5. Keywords for definition groups
The following SDF keywords are used to create definition groups in
the target namespace. All these definitions share some common
qualities as discussed in Section 4.6.
5.1. sdfObject
The sdfObject keyword denotes a group of zero or more Object
definitions. Object definitions may contain or include definitions
of Properties, Actions, Events declared for the object, as well as
data types (sdfData group) to be used in this or other Objects.
The qualities of an sdfObject include the common qualities,
additional qualities are shown in Table 6. None of these qualities
are required or have default values that are assumed if the quality
is absent.
+=============+===========+=============================+
| Quality | Type | Description |
+=============+===========+=============================+
| (common) | | Section 4.6 |
+-------------+-----------+-----------------------------+
| sdfProperty | property | zero or more named property |
| | | definitions for this object |
+-------------+-----------+-----------------------------+
| sdfAction | action | zero or more named action |
| | | definitions for this object |
+-------------+-----------+-----------------------------+
| sdfEvent | event | zero or more named event |
| | | definitions for this object |
+-------------+-----------+-----------------------------+
| sdfData | named-sdq | zero or more named data |
| | | type definitions that might |
| | | be used in the above |
+-------------+-----------+-----------------------------+
Table 6: Qualities of sdfObject
5.2. sdfProperty
The sdfProperty keyword denotes a group of zero or more Property
definitions.
Properties are used to model elements of state.
The qualities of a Property definition include the data qualities
(and thus the common qualities), see Section 4.7.
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5.3. sdfAction
The sdfAction keyword denotes a group of zero or more Action
definitions.
Actions are used to model commands and methods which are invoked.
Actions have parameter data that are supplied upon invocation.
The qualities of an Action definition include the common qualities,
additional qualities are shown in Table 7.
+===============+===========+============================+
| Quality | Type | Description |
+===============+===========+============================+
| (common) | | Section 4.6 |
+---------------+-----------+----------------------------+
| sdfInputData | map | data qualities of the |
| | | input data for an Action |
+---------------+-----------+----------------------------+
| sdfOutputData | map | data qualities of the |
| | | output data for an Action |
+---------------+-----------+----------------------------+
| sdfData | named-sdq | zero or more named data |
| | | type definitions that |
| | | might be used in the above |
+---------------+-----------+----------------------------+
Table 7: Qualities of sdfAction
"sdfInputData" defines the input data of the action. "sdfOutputData"
defines the output data of the action. As discussed in
Section 2.2.3, a set of data qualities with type "object" can be used
to substructure either data item, with optionality indicated by the
data quality "required".
5.4. sdfEvent
The sdfEvent keyword denotes zero or more Event definitions.
Events are used to model asynchronous occurrences that may be
communicated proactively. Events have data elements which are
communicated upon the occurrence of the event.
The qualities of sdfEvent include the common qualities, additional
qualities are shown in Table 8.
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+===============+===========+============================+
| Quality | Type | Description |
+===============+===========+============================+
| (common) | | Section 4.6 |
+---------------+-----------+----------------------------+
| sdfOutputData | map | data qualities of the |
| | | output data for an Event |
+---------------+-----------+----------------------------+
| sdfData | named-sdq | zero or more named data |
| | | type definitions that |
| | | might be used in the above |
+---------------+-----------+----------------------------+
Table 8: Qualities of sdfEvent
"sdfOutputData" defines the output data of the action. As discussed
in Section 2.2.4, a set of data qualities with type "object" can be
used to substructure the output data item, with optionality indicated
by the data quality "required".
5.5. sdfData
The sdfData keyword denotes a group of zero or more named data type
definitions (named-sdq).
An sdfData definition provides a reusable semantic identifier for a
type of data item and describes the constraints on the defined type.
It is not itself a declaration, i.e., it does not cause any of these
data items to be included in an affordance definition.
The qualities of sdfData include the data qualities (and thus the
common qualities), see Section 4.7.
6. High Level Composition
The requirements for high level composition include the following:
* The ability to represent products, standardized product types, and
modular products while maintaining the atomicity of Objects.
* The ability to compose a reusable definition block from Objects,
for example a single plug unit of an outlet strip with on/off
control, energy monitor, and optional dimmer objects, while
retaining the atomicity of the individual objects.
* The ability to compose Objects and other definition blocks into a
higher level thing that represents a product, while retaining the
atomicity of objects.
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* The ability to enrich and refine a base definition to have
product-specific qualities and quality values, e.g. unit, range,
and scale settings.
* The ability to reference items in one part of a complex definition
from another part of the same definition, for example to summarize
the energy readings from all plugs in an outlet strip.
6.1. Paths in the model namespaces
The model namespace is organized according to terms that are defined
in the definition files that are present in the namespace. For
example, definitions that originate from an organization or vendor
are expected to be in a namespace that is specific to that
organization or vendor. There is expected to be an SDF namespace for
common SDF definitions used in OneDM.
The structure of a path in a namespace is defined by the JSON
Pointers to the definitions in the files in that namespace. For
example, if there is a file defining an object "Switch" with an
action "on", then the reference to the action would be
"ns:/sdfObject/Switch/sdfAction/on" where "ns" is the namespace
prefix (short name for the namespace).
6.2. Modular Composition
Modular composition of definitions enables an existing definition
(could be in the same file or another file) to become part of a new
definition by including a reference to the existing definition within
the model namespace.
6.2.1. Use of the "sdfRef" keyword to re-use a definition
An existing definition may be used as a template for a new
definition, that is, a new definition is created in the target
namespace which uses the defined qualities of some existing
definition. This pattern will use the keyword "sdfRef" as a quality
of a new definition with a value consisting of a reference to the
existing definition that is to be used as a template. Optionally,
new qualities may be added and values of optional qualities and
quality values may be defined.
ISSUE: Do we want to enable qualities from the source definition to
be overridden in future versions? The above only says "added".
(Yes, we do want to enable overriding, but need to warn specifiers
not to use this in a way that contradicts the referenced semantics.)
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"sdfData":
"length" : {
"type": "number",
"minimum": 0,
"unit": "m"
"description": "There can be no negative lengths."
}
...
"cable-length" : {
"sdfRef": "#/sdfData/length"
"minimum": 0.05,
"description": "Cables must be at least 5 cm."
}
6.3. sdfThing
An sdfThing is a set of declarations and qualities that may be part
of a more complex model. For example, the object declarations that
make up the definition of a single socket of an outlet strip could be
encapsulated in an sdfThing, and the socket-thing itself could be
used in a declaration in the sdfThing definition for the outlet
strip.
sdfThing definitions carry semantic meaning, such as a defined
refrigerator compartment and a defined freezer compartment, making up
a combination refrigerator-freezer product.
An sdfThing may be composed of sdfObjects and other sdfThings.
The qualities of sdfThing are shown in Table 9.
+===========+========+=============+
| Quality | Type | Description |
+===========+========+=============+
| (common) | | Section 4.6 |
+-----------+--------+-------------+
| sdfThing | thing | |
+-----------+--------+-------------+
| sdfObject | object | |
+-----------+--------+-------------+
Table 9: Qualities of sdfThing
and sdfProduct
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6.4. sdfProduct
An sdfProduct provides the level of abstraction for representing a
unique product or a profile for a standardized type of product, for
example a "device type" definition with required minimum
functionality.
Products may be composed of Objects and Things at the high level, and
may include their own definitions of Properties, Actions, and Events
that can be used to extend or complete the included Object
definitions.
Product definitions may set optional defaults and constant values for
specific use cases, for example units, range, and scale settings for
properties, or available parameters for Actions.
The qualities of sdfProduct are the same as for sdfThing and are
shown in Table 9.
7. References
7.1. Normative References
[I-D.handrews-json-schema-validation]
Wright, A., Andrews, H., and B. Hutton, "JSON Schema
Validation: A Vocabulary for Structural Validation of
JSON", Work in Progress, Internet-Draft, draft-handrews-
json-schema-validation-02, 17 September 2019,
<http://www.ietf.org/internet-drafts/draft-handrews-json-
schema-validation-02.txt>.
[I-D.ietf-cbor-cddl-control]
Bormann, C., "Additional Control Operators for CDDL", Work
in Progress, Internet-Draft, draft-ietf-cbor-cddl-control-
00, 29 September 2020, <http://www.ietf.org/internet-
drafts/draft-ietf-cbor-cddl-control-00.txt>.
[IANA.senml]
IANA, "Sensor Measurement Lists (SenML)",
<http://www.iana.org/assignments/senml>.
[RFC0020] Cerf, V., "ASCII format for network interchange", STD 80,
RFC 20, DOI 10.17487/RFC0020, October 1969,
<https://www.rfc-editor.org/info/rfc20>.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC6901] Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed.,
"JavaScript Object Notation (JSON) Pointer", RFC 6901,
DOI 10.17487/RFC6901, April 2013,
<https://www.rfc-editor.org/info/rfc6901>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/info/rfc8610>.
[SPDX] "SPDX License List", <https://spdx.org/licenses/>.
[W3C.NOTE-curie-20101216]
Birbeck, M. and S. McCarron, "CURIE Syntax 1.0", World
Wide Web Consortium NOTE NOTE-curie-20101216, 16 December
2010, <https://www.w3.org/TR/2010/NOTE-curie-20101216>.
7.2. Informative References
[I-D.irtf-t2trg-rest-iot]
Keranen, A., Kovatsch, M., and K. Hartke, "RESTful Design
for Internet of Things Systems", Work in Progress,
Internet-Draft, draft-irtf-t2trg-rest-iot-06, 11 May 2020,
<http://www.ietf.org/internet-drafts/draft-irtf-t2trg-
rest-iot-06.txt>.
[OCF] "OCF Resource Type Specification",
<https://openconnectivity.org/specs/
OCF_Resource_Type_Specification.pdf>.
[OMA] "OMA LightweightM2M (LwM2M) Object and Resource Registry",
<http://www.openmobilealliance.org/wp/omna/lwm2m/
lwm2mregistry.html>.
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[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/info/rfc3339>.
[ZCL] "The ZigBee Cluster Library", Zigbee Wireless
Networking pp. 239-271,
DOI 10.1016/b978-0-7506-8597-9.00006-9, 2008,
<https://doi.org/10.1016/b978-0-7506-8597-9.00006-9>.
Appendix A. Formal Syntax of SDF
This appendix describes the syntax of SDF using CDDL [RFC8610]. Note
that this appendix was derived from Ari Keranen's "alt-schema" and
Michael Koster's "schema", with a view of covering the syntax that is
currently in use at the One Data Model "playground" repository.
This appendix shows the framework syntax only, i.e., a syntax with
liberal extension points. Since this syntax is nearly useless in
finding typos in an SDF specification, a second syntax, the
validation syntax, is defined that does not include the extension
points. The validation syntax can be generated from the framework
syntax by leaving out all lines containing the string "EXTENSION-
POINT"; as this is trivial, the result is not shown here.
This appendix makes use of CDDL "features" as defined in Section 4 of
[I-D.ietf-cbor-cddl-control]. A feature named "1.0" is used to
indicate parts of the syntax being deprecated towards SDF 1.1, and a
feature named "1.1" is used to indicate new syntax intended for SDF
1.1. Features whose names end in "-ext" indicate extension points
for further evolution.
start = sdf-syntax
sdf-syntax = {
info: sdfinfo ; don't *require* this in flexible syntax, though
? namespace: named<text>
? defaultNamespace: text
? sdfThing: named<thingqualities> ; Thing is a composition of objects that work together in some way
? sdfProduct: named<productqualities> ; Product is a composition of things and objects that can model a SKU-level instance of a product
? sdfObject: named<objectqualities> ; Object is a set of Properties, Actions, and Events that together perform a particular function
? sdfProperty: named<propertyqualities> ; Property represents the state of an instance of an object
? sdfAction: named<actionqualities> ; Action is a directive to invoke an application layer verb associated with an object
? sdfEvent: named<eventqualities> ; Event represents an occurence of something associated with an object
? sdfData: named<dataqualities> ; Data represents a piece of information that can be the state of a property or a parameter to an action or a signal in an event
EXTENSION-POINT<"top-ext">
}
sdfinfo = {
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title: text
version: text
copyright: text
license: text
EXTENSION-POINT<"info-ext">
}
; Shortcut for a map that gives names to instances of X (has text keys and values of type X)
named<X> = { * text => X }
EXTENSION-POINT<f> = ( * (text .feature f) => any ) ; only used in framework syntax
sdf-pointer = text ; .regexp curie-regexp -- TO DO!
pointer-list = [* sdf-pointer] ; ISSUE: no point in having an empty list, no? but used for sdfRequired in odmobject-multiple_axis_joystick.sdf.json
commonqualities = (
? description: text ; long text (no constraints)
? label: text ; short text (no constraints); default to key
? $comment: text ; source code comments only, no semantics
? sdfRef: sdf-pointer
? sdfRequired: pointer-list ; applies to qualities of properties, of data
)
; for building hierarchy
thingqualities = {
commonqualities,
? sdfObject: named<objectqualities>
? sdfThing: named<thingqualities>
EXTENSION-POINT<"thing-ext">
}
productqualities = thingqualities ; ISSUE: get rid of sdfProduct?
; for single objects
objectqualities = {
commonqualities,
? sdfProperty: named<propertyqualities>
? sdfAction: named<actionqualities>
? sdfEvent: named<eventqualities>
? sdfData: named<dataqualities>
EXTENSION-POINT<"object-ext">
}
propertyqualities = dataqualities ; the definitions in sdfData are declarations in sdfProperty
parameter-list =
pointer-list .feature (["1.0", "pointerlist-as-parameter"]) /
dataqualities .feature (["1.1", "dataqualities-as-parameter"])
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actionqualities = {
commonqualities,
? sdfInputData: parameter-list ; sdfRequiredInputData applies here (a bit redundant)
? sdfRequiredInputData: pointer-list
? sdfOutputData: parameter-list ; sdfRequired applies here
? sdfData: named<dataqualities> ; zero or more named data type definitions that might be used in the above
EXTENSION-POINT<"action-ext">
}
eventqualities = {
commonqualities
? sdfOutputData: parameter-list ; sdfRequired applies here
? sdfData: named<dataqualities> ; zero or more named data type definitions that might be used in the above
EXTENSION-POINT<"event-ext">
}
dataqualities = { ; also propertyqualities
commonqualities,
jsonschema,
? ("units" .feature "1.0") => text
? ("unit" .feature "1.1") => text
? scaleMinimum: number
? scaleMaximum: number
? observable: bool
? readable: bool
? writable: bool
? nullable: bool
? subtype: "byte-string" / "unix-time"
/ (text .feature "subtype-ext") ; EXTENSION-POINT
? contentFormat: text
EXTENSION-POINT<"data-ext">
}
allowed-types = number / text / bool / null
/ [* number] / [* text] / [* bool]
/ {* text => any}
/ (any .feature "allowed-ext") ; EXTENSION-POINT
compound-type = (
"type" => ("object" .feature "1.1"),
? required: [+text],
? properties: named<dataqualities>,
)
jsonschema = (
? (("type" => "number" / "string" / "boolean" / "integer" / "array")
// compound-type
// (type: text .feature "type-ext") ; EXTENSION-POINT
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)
? enum: [+ allowed-types] ; should validate against type
? const: allowed-types
? default: allowed-types
; number/integer constraints
? minimum: number
? maximum: number
? exclusiveMinimum: bool / number ; jso draft 4/7
? exclusiveMaximum: bool / number ; jso draft 4/7
? multipleOf: number ; ISSUE: Do we need this?
; text string constraints
? minLength: number
? maxLength: number
? pattern: text ; regexp
? format: "date-time" / "date" / "time"
/ "uri" / "uri-reference" / "uuid"
/ (text .feature "format-ext") ; EXTENSION-POINT
; array constraints
? minItems: number
? maxItems: number
? uniqueItems: bool
? items: { ;;; ultimately, this will be mostly recursive, but, for now
;;; let's find out what we actually need
? sdfRef: sdf-pointer ; import limited to the subset that we allow here...
? description: text ; long text (no constraints)
? $comment: text ; source code comments only, no semantics
; commonqualities, ; -- ISSUE: should leave this out for non-complex data types, but need the above three
? ((type: "number" / "string" / "boolean" / "integer") ; no "array"
// compound-type
// (type: text .feature "itemtype-ext") ; EXTENSION-POINT
)
; jso subset
? minimum: number
? maximum: number
? enum: [+ any]
? format: text
? minLength: number
? maxLength: number
EXTENSION-POINT<"items-ext">
}
)
Appendix B. json-schema.org Rendition of SDF Syntax
This appendix describes the syntax of SDF defined in Appendix A, but
using a version of the description techniques advertised on json-
schema.org [I-D.handrews-json-schema-validation].
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The appendix shows both the validation and the framework syntax.
Since most of the lines are the same between these two files, those
lines are shown only once, with a leading space, in the form of a
unified diff. Lines leading with a "-" are part of the validation
syntax, and lines leading with a "+" are part of the framework
syntax.
(The json-schema.org descriptions need to be regenerated after the
converter has been upgraded to handle the group choices introduced in
the latest CDDL.)
Acknowledgements
This draft is based on "sdf.md" and "sdf-schema.json" in the old one-
data-model "language" repository, as well as Ari Keranen's "alt-
schema" from the Ericsson Research "ipso-odm" repository (which is
now under subdirectory "sdflint" in the one-data model "tools"
repository).
Contributors
Ari Keränen
Ericsson
FI-02420 Jorvas
Finland
Email: ari.keranen@ericsson.com
Wouter van der Beek
Cisco Systems
Eastpoint Business Park
Alfie Byrne Road
Dublin 3
Ireland
Email: wovander@cisco.com
Authors' Addresses
Michael Koster (editor)
SmartThings
665 Clyde Avenue
Mountain View, 94043
United States of America
Phone: +1-707-502-5136
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Email: Michael.Koster@smartthings.com
Carsten Bormann (editor)
Universität Bremen TZI
Postfach 330440
D-28359 Bremen
Germany
Phone: +49-421-218-63921
Email: cabo@tzi.org
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