On the Difference between Information Models and Data Models
RFC 3444

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Network Working Group                                            A. Pras
Request for Comments: 3444                          University of Twente
Category: Informational                                 J. Schoenwaelder
                                                University of Osnabrueck
                                                            January 2003

                       On the Difference between
                   Information Models and Data Models

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   There has been ongoing confusion about the differences between
   Information Models and Data Models for defining managed objects in
   network management.  This document explains the differences between
   these terms by analyzing how existing network management model
   specifications (from the IETF and other bodies such as the
   International Telecommunication Union (ITU) or the Distributed
   Management Task Force (DMTF)) fit into the universe of Information
   Models and Data Models.

   This memo documents the main results of the 8th workshop of the
   Network Management Research Group (NMRG) of the Internet Research
   Task Force (IRTF) hosted by the University of Texas at Austin.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
   3.  Information Models . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Data Models  . . . . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 6
   6.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 6
   7.  Normative References . . . . . . . . . . . . . . . . . . . . . 6
   8.  Informative References . . . . . . . . . . . . . . . . . . . . 7
   9.  Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 7
   10. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 8

Pras & Schoenwaelder         Informational                      [Page 1]
RFC 3444           Information Models and Data Models       January 2003

1. Introduction

   Currently multiple languages exist to define managed objects.
   Examples of such languages are the Structure of Management
   Information (SMI) [1], the Structure of Policy Provisioning
   Information (SPPI) [2] and, within the DMTF, the Managed Object
   Format (MOF) [3].  Despite the fact that multiple languages exist, a
   number of people still believe that none of these languages really
   suits all needs.

   There have been many discussions to understand the advantages and
   disadvantages, as well as the main differences, between various
   languages.  For instance, the IETF organized a BoF on "Network
   Information Modeling" (NIM) at its 48th meeting (Pittsburgh, August
   2000).  During these discussions, it turned out that people had a
   different understanding of the main terms, which caused confusion and
   long arguments.  In particular, the meaning of the terms "Information
   Model" (IM) and "Data Model" (DM) turned out to be controversial.

   In an attempt to address this issue, the IRTF Network Management
   Research Group (NMRG) dedicated its 8th workshop (Austin, December
   2000) to harmonizing the terminology used in information and data
   modeling.  Attendees included experts from the IETF, DMTF and ITU, as
   well as academics who do research in this field (see the
   Acknowledgments section for a list of participants).  The main
   outcome of this successful workshop -- a better understanding of the
   terms "Information Model" and "Data Model" -- is presented in this
   document.

   Short definitions of these terms can also be found elsewhere (e.g.,
   in RFC 3198 [8]).  Compared to most other documents, this one
   explains the rationale behind the proposed definitions and provides
   examples.

2. Overview

   One of the key observations made at the NMRG workshop was that IMs
   and DMs are different because they serve different purposes.

   The main purpose of an IM is to model managed objects at a conceptual
   level, independent of any specific implementations or protocols used
   to transport the data.  The degree of specificity (or detail) of the
   abstractions defined in the IM depends on the modeling needs of its
   designers.  In order to make the overall design as clear as possible,
   an IM should hide all protocol and implementation details.  Another
   important characteristic of an IM is that it defines relationships
   between managed objects.

Pras & Schoenwaelder         Informational                      [Page 2]
RFC 3444           Information Models and Data Models       January 2003

   DMs, conversely, are defined at a lower level of abstraction and