ISO/IEC 21000-2:2003
(Main)Information technology — Multimedia framework (MPEG-21) — Part 2: Digital Item Declaration
Information technology — Multimedia framework (MPEG-21) — Part 2: Digital Item Declaration
ISO/IEC 21000 (MPEG-21) defines an open framework for multimedia delivery and consumption, with both the content creator and content consumer as focal points. The vision for MPEG-21 is to define a multimedia framework to enable transparent and augmented use of multimedia resources across a wide range of networks and devices used by different communities. The basic architectural concept in MPEG-21 is the Digital Item. Digital Items are structured digital objects, including a standard representation, identification and metadata. They are the basic unit of transaction in the MPEG-21 framework. More concretely, a Digital Item is a combination of resources (such as videos, audio tracks, images, etc), metadata (such as descriptors, identifiers, etc), and structure (describing the relationships between resources). This second part of MPEG-21 (ISO/IEC 21000-2:2003) specifies a uniform and flexible abstraction and interoperable schema for declaring the structure and makeup of Digital Items. Digital Items are declared using the Digital Item Declaration Language (DIDL) and declaring a Digital Item involves specifying its resources, metadata and their interrelationships. Within ISO/IEC 21000-2:2003 this Digital Item Declaration (DID) technology is described in four main sections: Model: The Digital Item Declaration Model describes a set of abstract terms and concepts to form a useful model for defining Digital Items. Representation: The Digital Item Declaration Language (DIDL) is based upon the terms and concepts defined in the above model. It contains the normative description of the syntax and semantics of each of the DIDL elements, as represented in XML. This section also contains some short non-normative examples for illustrative purposes. Schema: The complete normative XML schema for DIDL comprising the entire grammar of the DID representation. Detailed Examples: Illustrative (non-normative) examples of DIDL documents are provided to aid in understanding the use of the specification and its potential applications.
Technologies de l'information — Cadre multimédia (MPEG-21) — Partie 2: Déclaration d'article numérique
General Information
Relations
Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 21000-2
First edition
2003-03-15
Information technology — Multimedia
framework (MPEG-21) —
Part 2:
Digital Item Declaration
Technologies de l'information — Cadre multimédia (MPEG-21) —
Partie 2: Déclaration d'article numérique
Reference number
ISO/IEC 21000-2:2003(E)
©
ISO/IEC 2003
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ISO/IEC 21000-2:2003(E)
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ISO/IEC 21000-2:2003(E)
Contents Page
Foreword . vii
Executive Summary for MPEG-21. viii
1 Scope. 1
1.1 Organization of the document . 1
2 Normative references. 1
3 Terms and definitions . 2
3.1 Digital Item . 2
4 Conventions. 2
4.1 Naming convention . 2
4.2 Documentation convention . 2
5 Symbols and abbreviated terms. 4
6 Digital Item Declaration Model. 5
6.1 Purpose and Overview. 5
6.2 Abstract Model. 5
6.2.1 Container. 5
6.2.2 Item . 5
6.2.3 Component. 6
6.2.4 Anchor . 6
6.2.5 Descriptor. 6
6.2.6 Condition. 6
6.2.7 Choice. 6
6.2.8 Selection. 6
6.2.9 Annotation. 7
6.2.10 Assertion . 7
6.2.11 Resource . 7
6.2.12 Fragment . 7
6.2.13 Statement . 7
6.2.14 Predicate . 7
7 Digital Item Declaration Representation . 9
7.1 Introduction. 9
7.1.1 DIDL Overview . 9
7.2 DIDL Definition. 10
7.2.1 Validation . 10
7.2.2 Canonicalization. 10
7.2.3 Element Descriptions. 10
7.2.4 . 11
7.2.5 . 12
7.2.6 . 13
7.2.7 . 14
7.2.8 . 16
7.2.9 . 17
7.2.10 . 19
7.2.11 . 20
7.2.12 . 23
7.2.13 . 25
7.2.14 . 27
7.2.15 . 28
7.2.16 . 30
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ISO/IEC 21000-2:2003(E)
7.2.17 . 33
7.2.18 . 35
8 The Digital Item Declaration XML Schema Definition.37
9 Example Digital Items expressed in DIDL (informative) . 44
9.1 Example 1: Using MPEG-7 descriptors in conjunction with a Choice. 44
9.2 Example 2: Expressing the same set of metadata in different descriptor formats. 46
9.3 Example 3: A digital music album . 47
9.4 Example 4: Implementing numeric comparisons in Item configuration . 58
Annex A (informative) Patent statements. 61
Bibliography. 62
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ISO/IEC 21000-2:2003(E)
List of Tables Page
Table 1 — Example element specification .3
Table 2 — DIDL element syntax .11
Table 3 — DECLARATIONS element syntax.12
Table 4 — CONTAINER element syntax .13
Table 5 — ITEM element syntax.15
Table 6 — COMPONENT element syntax .16
Table 7 — RESOURCE element syntax.17
Table 8 — DESCRIPTOR element syntax .19
Table 9 — STATEMENT element syntax.20
Table 10 — ANCHOR element syntax.24
Table 11 — CHOICE element syntax.26
Table 12 — SELECTION element syntax.27
Table 13 — CONDITION element syntax.28
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ISO/IEC 21000-2:2003(E)
List of Figures Page
Figure 1 — Example element syntax diagram . 4
Figure 2 — Example Digital Item Declaration model . 8
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ISO/IEC 21000-2:2003(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission)
form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC
participate in the development of International Standards through technical committees established by the
respective organization to deal with particular fields of technical activity. ISO and IEC technical committees
collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in
liaison with ISO and IEC, also take part in the work. In the field of information technology, ISO and IEC have
established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International Standards
adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the national bodies casting a vote.
ISO/IEC 21000-2 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
ISO/IEC 21000 consists of the following parts, under the general title Information technology — Multimedia
framework (MPEG-21):
Part 1: Vision, Technologies and Strategy
Part 2: Digital Item Declaration
Part 3: Digital Item Identification
Part 4: Intellectual Property Management and Protection (IPMP)
Part 5: Rights Expression Language
Part 6: Rights Data Dictionary
Part 7: Digital Item Adaptation
Part 8: Reference Software
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ISO/IEC 21000-2:2003(E)
Executive Summary for MPEG-21
Today, many elements exist to build an infrastructure for the delivery and consumption of multimedia content.
There is, however, no “big picture” to describe how these elements, either in existence or under development,
relate to each other. The aim for MPEG-21 is to describe how these various elements fit together. Where gaps exist,
MPEG-21 will recommend which new standards are required. ISO/IEC JTC 1/SC 29/WG 11 (MPEG) will then
develop new standards as appropriate while other relevant standards may be developed by other bodies. These
specifications will be integrated into the multimedia framework through collaboration between MPEG and these
bodies.
The result is an open framework for multimedia delivery and consumption, with both the content creator and
content consumer as focal points. This open framework provides content creators and service providers with equal
opportunities in the MPEG-21 enabled open market. This will also be to the benefit of the content consumer
providing them access to a large variety of content in an interoperable manner.
The vision for MPEG-21 is to define a multimedia framework to enable transparent and augmented use of
multimedia resources across a wide range of networks and devices used by different communities.
This second part of MPEG-21 (ISO/IEC 21000-2) specifies the mechanism for declaring the structure and makeup
of Digital Items.
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INTERNATIONAL STANDARD ISO/IEC 21000-2:2003(E)
Information technology — Multimedia framework (MPEG-21) —
Part 2:
Digital Item Declaration
1 Scope
This document describes the MPEG-21 Digital Item Declaration technology, which is part 2 of the MPEG-21
standard.
1.1 Organization of the document
This technology is described in three normative clauses:
• Model: The Digital Item Declaration Model (clause 6) describes a set of abstract terms and concepts
to form a useful model for defining Digital Items. Within this model, a Digital Item is the
digital representation of “a work”, and as such, it is the thing that is acted upon (managed,
described, exchanged, collected, etc.) within the model.
• Representation: Clause 7 contains the normative description of the syntax and semantics of each of the
Digital Item Declaration elements, as represented in XML. This clause also contains some
non-normative examples for illustrative purposes.
• Schema: Clause 8 contains the normative XML schema comprising the entire grammar of the Digital
Item Declaration representation in XML.
In addition, illustrative (non-normative) examples are provided.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references,
only the edition cited applies. For undated references, the latest edition of the referenced document (including any
amendments) applies.
Extensible Markup Language 1.0 (Second Edition), W3C Recommendation, 6 October 2000
XML Schema Part 1: Structures and Part 2: Datatypes, W3C Recommendation, 2 May 2001
Canonical XML Version 1.0, W3C Recommendation, 15 March 2001
Uniform Resource Identifiers (URI): Generic Syntax, IETF RFC 2396, 1998
Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies. IETF RFC 2045, 1996
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ISO/IEC 21000-2:2003(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 Digital Item
In ISO/IEC 21000-1:2001 (part 1 of MPEG-21: Vision, Technologies and Strategy), Digital Items are defined as
structured digital objects, including a standard representation and identification, and meta-data. This entity is the
fundamental unit of distribution and transaction within the MPEG-21 framework as a whole; it has, however, no
further technical meaning. Within this document (part 2 of MPEG-21: Digital Item Declaration), an item is a
grouping of sub-items and/or components that are bound to relevant descriptors, as defined within the Digital Item
Declaration Model. The term item is a technical term, and is, as such, a narrower term than Digital Item. In
conclusion, the use of the two different terms Digital Item and item within MPEG-21 is consistent and intended.
4 Conventions
4.1 Naming convention
It should be noted that the Digital Item Declaration Model (clause 6) contains the concept names that are used
throughout the MPEG-21 standard. As such, this model should be considered to be the “ultimate arbiter” of these
MPEG-21 concept names.
4.2 Documentation convention
The semantics of each element in the Digital Item Declaration Model is specified using the constructs provided by
EBNF [4], and is shown in this document using a specific font and background:
element ::= (part1 | part2)+ part3*
The syntax of each element in the Digital Item Declaration Representation is specified using the constructs
provided by XML Schema [2].
Element names and attribute names in the representation are in SMALL CAPS. Throughout the document, italics are
used when referring to elements defined in the Digital Item Declaration Model (see clause 4), hereafter known as
the Model.
The syntax of each element in the Digital Item Declaration representation is specified using the following format.
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ISO/IEC 21000-2:2003(E)
Diagram
Children
Used by
Name Type Description
Attributes
ID ID A unique ID value, which can be referenced by another element.
Source
Table 1 — Example element specification
The Language Definition clause contains syntax diagrams for each element. Here is an example syntax diagram
with annotations:
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ISO/IEC 21000-2:2003(E)
Optional child
Sequence group
Required child
Parent element
Optional
unbounded
child
Required
unbounded
Choice group
child
Required child
with children
Figure 1 — Example element syntax diagram
Non-normative examples are included in separate clauses, and are shown in this document using a separate font
and background:
example element content
5 Symbols and abbreviated terms
For the purposes of this document, the following abbreviations apply.
DID: Digital Item Declaration
DIDL: Digital Item Declaration Language
EBNF: Extended Backus-Naur Form
IANA: Internet Assigned Numbers Authority
IPMP: Intellectual Property Management and Protection
JPEG: Joint Photographic Experts Group
MPEG: Moving Picture Experts Group
MPEG-21: ISO/IEC 21000 (all parts)
MP3: MPEG-1/2 layer III (audio coding)
URI: Uniform Resource Identifier (IETF Standard is RFC 2396)
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ISO/IEC 21000-2:2003(E)
URL: Uniform Resource Locator (IETF Standard is RFC 1738)
URN: Uniform Resource Name (IETF Standard is RFC 2396)
XML: Extensible Markup Language (W3C Recommendation)
6 Digital Item Declaration Model
6.1 Purpose and Overview
The purpose of this clause is to describe a set of abstract terms and concepts to form a useful model for defining
Digital Items. Within this model, a Digital Item is the digital representation of “a work”, and as such, it is the thing
that is acted upon (managed, described, exchanged, collected, etc.) within the model. The goal of this model is to
be as flexible and general as possible, while providing for the “hooks” that enable higher level functionality and
interoperability. This, in turn, will allow the model to serve as a key foundation in the building of higher level models
in other MPEG-21 elements (such as Identification or IPMP). This model specifically does not define a language in
and of itself. Instead, the model helps to provide a common set of abstract concepts and terms that can be used to
define such a scheme, or to perform mappings between existing schemes capable of Digital Item Declaration, for
comparison purposes.
6.2 Abstract Model
Please note that in the descriptions below, the defined elements in italics are intended to be unambiguous terms
within this model. The prose descriptions define the semantic “meaning” of the terms, and the EBNF
representations define the precise intended relationship or structure between terms within the model.
6.2.1 Container
A container is a structure that allows items and/or containers to be grouped. These groupings of items and/or
containers can be used to form logical packages (for transport or exchange) or logical shelves (for organization).
Descriptors allow for the “labelling” of containers with information that is appropriate for the purpose of the grouping
(e.g. delivery instructions for a package, or category information for a shelf).
It should be noted that a container itself is not an item; containers are groupings of items and/or containers.
container ::= container* item* descriptor*
6.2.2 Item
An item is a grouping of sub-items and/or components that are bound to relevant descriptors. Descriptors contain
information about the item, as a representation of a work. Items may contain choices, which allow them to be
customized or configured. Items may be conditional (on predicates asserted by selections defined in the choices).
An item that contains no sub-items can be considered an entity -- a logically indivisible work. An item that does
contain sub-items can be considered a compilation -- a work composed of potentially independent sub-parts. Items
may also contain annotations to their sub-parts.
The relationship between items and Digital Items (as defined in ISO/IEC 21000-1:2001, MPEG-21 Vision,
Technologies and Strategy) could be stated as follows: items are declarative representations of Digital Items.
item ::= (item | component)* choice* descriptor* condition* annotation*
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ISO/IEC 21000-2:2003(E)
6.2.3 Component
A component is the binding of a resource to a set of descriptors. These descriptors are information related to all or
part of the specific resource instance. Such descriptors will typically contain control or structural information about
the resource (such as bit rate, character set, start points or encryption information) but not information describing
the “content” within.
It should be noted that a component itself is not an item; components are building blocks of items.
component ::= resource descriptor* anchor* condition*
6.2.4 Anchor
An anchor binds descriptors to a fragment, which corresponds to a specific location or part of a resource.
anchor ::= fragment descriptor* condition*
6.2.5 Descriptor
A descriptor associates information with the enclosing element. This information may be a component (such as a
thumbnail of an image, or a text component), or a textual statement.
descriptor ::= descriptor* (component | statement) condition*
6.2.6 Condition
A condition describes the enclosing element as being optional, and links it to the selection(s) that affect its inclusion.
Multiple predicates within a condition are combined as a conjunction (an AND relationship). Any predicate can be
negated within a condition. Multiple conditions associated with a given element are combined as a disjunction (an
OR relationship) when determining whether to include the element.
condition ::= predicate+
6.2.7 Choice
A choice describes a set of related selections that can affect the configuration of an item. The selections within a
choice are either exclusive (choose exactly one) or inclusive (choose any number, including all or none).
choice ::= selection+ descriptor* condition*
6.2.8 Selection
A selection describes a specific decision that will affect one or more conditions somewhere within an item. If the
selection is chosen, its predicate becomes true; if it is not chosen, its predicate becomes false; if it is left unresolved,
its predicate is undecided.
selection ::= predicate descriptor* condition*
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ISO/IEC 21000-2:2003(E)
6.2.9 Annotation
An annotation describes a set of information about another identified element of the model without altering or
adding to that element. The information can take the form of assertions, descriptors, and anchors.
annotation ::= assertion* descriptor* anchor*
6.2.10 Assertion
An assertion defines a full or partially configured state of a choice by asserting true, false or undecided values for
some number of predicates associated with the selections for that choice.
assertion ::= predicate*
6.2.11 Resource
A resource is an individually identifiable asset such as a video or audio clip, an image, or a textual asset. A
resource may also potentially be a phy
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