ISO/IEC 21000-23:2022

Information technology - Multimedia framework (MPEG-21) - Part 23: Smart Contracts for Media

This document specifies the means (e.g. protocols and application programming interfaces) for converting MPEG-21 XML and RDF media contracts (ISO/IEC 21000-19, ISO/IEC 21000-20, and ISO/IEC 21000-21) to smart contracts executable on existing DLT environments.

Technologies de l'information — Cadre multimédia (MPEG-21) — Partie 23: Contrats intelligents pour les médias

General Information

• Status: Published
• Publication Date: 17-Nov-2022
• ICS: 35.040.40 - Coding of audio, video, multimedia and hypermedia information
• Technical Committee: ISO/IEC JTC 1/SC 29 - Coding of audio, picture, multimedia and hypermedia information
• Drafting Committee: ISO/IEC JTC 1/SC 29/WG 3 - MPEG Systems
• Current Stage: 6060 - International Standard published
• Start Date: 18-Nov-2022
• Due Date: 27-Jan-2023
• Completion Date: 18-Nov-2022

Overview - ISO/IEC 21000-23:2022 (MPEG-21 Part 23: Smart Contracts for Media)

ISO/IEC 21000-23:2022 defines a framework for converting MPEG-21 media contracts (expressed in XML and RDF using MPEG-21 CEL and MCO) into smart contracts executable on existing Distributed Ledger Technology (DLT) environments, and vice versa. The standard specifies the protocols, application programming interfaces (APIs), and components needed to enable bidirectional conversion between MPEG-21 Contract Expression Language (CEL) / Media Contract Ontology (MCO) documents and DLT-executable smart contracts, while supporting related runtime features such as token and payment management.

Key Topics and Technical Requirements

• Bidirectional conversion: Methods for converting MPEG-21 CEL/MCO contracts to smart contracts and converting smart contracts back to MPEG-21 CEL/MCO.
• Parser and generator APIs: Defined APIs for MPEG-21 CEL/MCO parsers and generators to automate transformations.
• Smart contract generator & parser: Components to produce DLT-targeted smart contract code and to interpret smart contracts back into MPEG-21 representations.
• DLT tokens and payments manager: Interfaces and workflow descriptions for integrating tokenization and on‑ledger payments with media contracts.
• Contractual object model: API surface for media contractual objects (Contract, Party, Deontic, Action, Object, Fact, etc.) as identified in the standard.
• Narrative contracts: Support for human-readable narrative constructs alongside machine-executable clauses.
• Reference software and conformance: Guidance on template contracts, example parsers/generators, OpenAPI bindings, demo implementations and conformance testing.
• Namespaces, conventions, and data modelling: Representation conventions (classes, namespace prefixes) to ensure consistent mapping between XML/RDF and smart contract semantics.

Practical Applications and Who Uses This Standard

ISO/IEC 21000-23 enables interoperability between traditional media-license representations and blockchain/DLT-based automation. Typical applications:

• Automated licensing and royalty payments - convert standardized media rights into smart contracts that trigger payments and rights delivery.
• Tokenization of media assets - map MPEG-21 contract terms to on-chain tokens and payment logic.
• Interoperable rights management - ensure consistent semantics between XML/RDF contract stores and DLT environments.
• Platform and middleware development - streaming platforms, rights-management systems, and blockchain integrators use the APIs and converters for deployment.

Primary users:

• Media companies, rights holders, and collective management organizations
• Blockchain/DLT developers and integration engineers
• DRM and content distribution platform architects
• Standards implementers and legal-technology teams

Related Standards

• ISO/IEC 21000-19, -20, -21 - MPEG-21 contract expression and ontology documents (CEL and MCO) that ISO/IEC 21000-23 maps to/from DLT smart contracts.

Keywords: ISO/IEC 21000-23, MPEG-21, smart contracts for media, media contracts, DLT, blockchain, CEL, MCO, XML, RDF, tokenization, API, contract conversion, OpenAPI.

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 21000-23
First edition
2022-11
Information technology — Multimedia
framework (MPEG-21) —
Part 23:
Smart Contracts for Media
Technologies de l'information — Cadre multimédia (MPEG-21) —
Partie 23: Contrats intelligents pour les médias
Reference number
© ISO/IEC 2022
© ISO/IEC 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
© ISO/IEC 2022 – All rights reserved

Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols, and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 3
4 Conventions . 3
4.1 Classes representation . 3
4.2 Namespace prefixes . 4
5 Overview . 5
5.1 General aspects . 5
5.2 Relationships between MPEG-21 CEL/MCO and DLTs . 5
6 Bidirectional conversion between MPEG-21 CEL/MCO contracts and smart
contracts for media . 8
6.1 Conversion from MPEG-21 CEL/MCO contracts to smart contracts for media . 9
6.1.1 MPEG-21 CEL/MCO parser . 9
6.1.2 Smart contract generator . 10
6.1.3 DLT tokens and payments manager . 10
6.2 Conversion from smart contracts for media to MPEG-21 CEL/MCO contracts . 11
6.2.1 Smart contract parser . 11
6.2.2 MPEG-21 CEL/MCO generator . 11
7 Narrative contracts .12
8 API for media contractual objects .12
8.1 Contract . 13
8.1.1 Contract .13
8.1.2 Encryptable . 17
8.2 Party . 18
8.2.1 Party . 18
8.2.2 Person/User . 19
8.2.3 CELPerson . 20
8.2.4 MCOUser . .20
8.2.5 Organization . . . 21
8.3 Deontic .22
8.3.1 DeonticStructuredClause/DeonticExpression .22
8.3.2 TextClause .23
8.3.3 CELDeonticStructuredBlock . 24
8.3.4 CELDeonticStructuredClause . 25
8.3.5 CELCondition . 26
8.3.6 MCODeonticExpression . 27
8.3.7 Permission .28
8.3.8 CELPermission .29
8.3.9 MCOPermission .29
8.4 Action .30
8.4.1 Act/GenericAction/Action .30
8.4.2 Trade . 33
8.4.3 Provide . 33
8.4.4 Payment .34
8.4.5 Notify . 35
8.4.6 UserDefinedAction . 36
8.5 Object . 37
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8.5.1 Object . 37
8.5.2 Item . 37
8.5.3 IPEntity .38
8.5.4 Event . 39
8.5.5 Segment .40
8.5.6 Service .40
8.5.7 SubjectWrapperObject . 41
8.5.8 Track . 42
8.5.9 Interval. 43
8.6 Fact . 43
8.6.1 Constraint/Fact . 43
8.6.2 FactComposition .46
8.6.3 ActionEventFact . 47
8.6.4 TogetherWith .48
8.6.5 AccessPolicy .48
8.6.6 DeliveryModality .49
8.6.7 Device .50
8.6.8 IPEntityContext . 51
8.6.9 Language . 51
8.6.10 Length . 52
8.6.11 MaterialFormat . 52
8.6.12 Means.54
8.6.13 Runs .54
8.6.14 ServiceAccessPolicy. 55
8.6.15 ServiceChannelContext .56
8.6.16 SpatialContext . . 57
8.6.17 TemporalContext . 57
8.6.18 UserTimeAccess .58
8.6.19 UserDefinedFact . 59
9 API for MPEG-21 CEL/MCO parser .60
10 API for MPEG-21 CEL/MCO generator .60
11 Reference software and conformance .60
11.1 MPEG-21 template contracts . 62
11.1.1 Open Music Initiative use cases . 62
11.2 MPEG-21 Contract Expression Language .63
11.2.1 MPEG-21 CEL parser .63
11.2.2 MPEG-21 CEL generator .63
11.2.3 MPEG-21 CEL contracts to smart contracts for media (forward conversion) .63
11.2.4 Smart contracts for media to MPEG-21 CEL contracts (backward
conversion) .65
11.3 MPEG-21 Media Contract Ontology .66
11.3.1 MPEG-21 MCO parser . 67
11.3.2 MPEG-21 MCO generator .68
11.3.3 MPEG-21 MCO contracts to smart contracts for media (forward conversion) .68
11.3.4 Smart contracts for media to MPEG-21 MCO contracts (backward
conversion) .73
11.4 OpenAPI and demo . 75
11.4.1 OpenAPI . 75
11.4.2 MPEG-21 MCO OpenAPI server . 76
11.4.3 MPEG-21 CEL server . . 76
11.4.4 Demo . 76
Bibliography .78
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© ISO/IEC 2022 – All rights reserved

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.
The procedures used to develop this document and those intended for its further maintenance
are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria
needed for the different types of document should be noted. This document was drafted in
accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives or
www.iec.ch/members_experts/refdocs).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC
list of patent declarations received (see https://patents.iec.ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see
www.iso.org/iso/foreword.html. In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
A list of all parts in the ISO/IEC 21000 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards
body. A complete listing of these bodies can be found at www.iso.org/members.html and
www.iec.ch/national-committees.
v
© ISO/IEC 2022 – All rights reserved

Introduction
The Moving Picture Experts Group (MPEG) standards include a set of RDF ontologies for the
codification of intellectual property (IP) rights information related to media. The ISO/IEC 21000-19
Media Value Chain Ontology (MVCO) which facilitates rights tracking for fair, timely, and transparent
payment of royalties by capturing user roles and their permissible actions on a particular IP entity.
The ISO/IEC 21000-19/AMD1 Audio Value Chain Ontology (AVCO) which extends MVCO functionality
related to the description of IP entities in the audio domain (e.g. multitrack audio and time segments).
The ISO/IEC 21000-21 Media Contract Ontology (MCO) which facilitates the conversion of narrative
contracts to digital ones related to exploitation of IP rights, payments and notifications. With respect
to the latter, an equivalent standard has also been developed but using XML schemas, known as
ISO/IEC 21000-20 Contract Expression Language (CEL).
Furthermore, the axioms in these XML schemas and RDF ontologies can drive the execution of rights-
related workflows in controlled environments, for example, Distributed Ledger Technologies (DLTs),
where transparency and interoperability are favored toward fair trade of music and media. Thus, the
aim of this document is to provide the means (e.g. protocols and application programming interfaces)
for converting these XML and RDF media contracts to smart contracts executable on existing DLT
environments.
By doing this conversion in a standard way for several smart contract languages it is going to ensure
that MPEG schemas and ontologies prevail as the interlingua for transferring verified contractual data
from one DLT to another.
vi
© ISO/IEC 2022 – All rights reserved

INTERNATIONAL STANDARD ISO/IEC 21000-23:2022(E)
Information technology — Multimedia framework (MPEG-
21) —
Part 23:
Smart Contracts for Media
1 Scope
This document specifies the means (e.g. protocols and application programming interfaces) for
converting MPEG-21 XML and RDF media contracts (ISO/IEC 21000-19, ISO/IEC 21000-20, and
ISO/IEC 21000-21) to smart contracts executable on existing DLT environments.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
ISO/IEC 21000-19, Information technology — Multimedia framework (MPEG-21) — Part 19: Media Value
Chain Ontology
ISO/IEC 21000-20, Information technology — Multimedia framework (MPEG-21) — Part 20: Contract
Expression Language
ISO/IEC 21000-21, Information technology — Multimedia framework (MPEG-21) — Part 21: Media
contract ontology
3 Terms, definitions, symbols, and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
DLT
distributed ledger technology
distributed network of computers, ideally organized in a decentralized way, mutually agreeing on a
common state while tolerating failures (including malicious behavior) to some extent
3.1.2
smart contract
code deployed in a DLT or the source code from which such code was compiled
Note 1 to entry: The execution of smart contract instructions is distributed among the nodes of the DLT in which
it is deployed to. This execution is triggered via a DLT transaction and produces a change in the DLT state.
© ISO/IEC 2022 – All rights reserved

3.1.3
smart contract language
programming language used for creating the code of a smart contract, that is then compiled in another
code deployable to a specific DLT
3.1.4
smart contract template
source code of a smart contract written using a specific smart contract language for defining a common
behavior.
3.1.5
smart contract specification
set of information needed for the deployment of a smart contract and for populating the data structures
that the smart contract instructions are interacting with
3.1.6
DLT address
product of a cryptographic schema operation used to represent identities in a DLT
3.1.7
DLT governance
specification indicating the set of rules followed by the specific DLT protocol
3.1.8
token
object stored in a DLT and managed through one or more smart contracts, representing unique tangible
or intangible media assets, possessions, and accountable items
3.1.9
fungible token
token being changeable with other tokens
3.1.10
non-fungible token
token being non interchangeable with other tokens
3.1.11
MPEG-21 CEL/MCO contract
contract represented using ISO/IEC 21000-19, ISO/IEC 21000-20 and ISO/IEC 21000-21 elements
3.1.12
media contractual objects
set of machine-readable objects extracted from a specific MPEG-21 CEL/MCO contract
3.1.13
smart contract for media
deployed smart contract that is the result of the conversion process from a specific MPEG-21 CEL/MCO
contract
3.1.14
parser
software component that extracts a set of media contractual objects from an MPEG-21 CEL/MCO
contract or a smart contract for media
3.1.15
generator
software component that from a set of media contractual objects generates an MPEG-21 CEL/MCO
contract or a smart contract specification
© ISO/IEC 2022 – All rights reserved

3.1.16
DLT tokens and payments manager
component deploying a smart contract for media on a specific DLT
3.1.17
contract developer
actor providing the means to generate an MPEG-21 CEL/MCO contract or a smart contract in a specific
smart contract language (e.g. smart contract templates)
3.1.18
DLT system engineer
actor providing the information needed to deploy a smart contract in a specific DLT (e.g. DLT addresses
and governance)
3.2 Abbreviated terms
MVCO media value chain ontology
AVCO audio value chain ontology
CEL contract expression language
MCO media contract ontology
CEL/MCO ISO/IEC 21000-19, ISO/IEC 21000-20, and ISO/IEC 21000-21
IP intellectual property
API application programming interface
4 Conventions
4.1 Classes representation
The following conventions derive from the Object-Oriented Programming paradigm. In this sense
Application Programming Interfaces (APIs) are represented in terms of Classes definitions and Objects.
An Object is an instantiation of a Class while a Class contains the following properties:
— Name of the represented object.
— Type of the represented object. An object Type may be:
— Abstract which is only showing essential information with respect to an interface, but it cannot
be implemented; or,
— Concrete which is a complete specification that can be implemented.
— Hierarchy with respect to the other objects; it also introduces the sub-class which is a class that
inherits the complete set of fields and methods of its super-class.
— Fields which describe the attributes associated to the represented object; Fields consist of a specific
Field Type and the number of Occurrences.
— Methods which are operations performed by manipulating the object Fields; Methods accept as
input a specific set of Parameter Types and provide as output a specific set of Return Types.
In the following, Table 1 shows the notation for representing Classes with respect to MPEG-21 CEL/
MCO objects, while Table 2 describes the Types used for Fields, Parameters and Returns.
© ISO/IEC 2022 – All rights reserved

Table 1 — Classes notation with respect to MPEG-21 CEL/MCO
Class CEL MCO
Name Type and Hierarchy
ClassName1 Abstract or Concrete, sub-class of referenceToCELObject1 referenceToMCOObject1
ClassName2
Fields
Type Field and Description Occ.
FieldName1Type FieldName1 0, 1 or referenceToCELObject2 referenceToMCOObject2
1, n
Methods
Parameters Method and Description Return
ParameterType1 method1() ReturnType1
Table 2 — Types used for Fields, Parameters and Returns
Type Description
string A sequence of characters
ushort An unsigned integer number represented through 2 bytes
ulong An unsigned integer number represented through 4 or 8 bytes
float A floating-point number, that is a number that can contain a
fractional part, represented through 4 or 8 bytes
enum A set of enumerated named elements
boolean A dyadic value with two possible values, True and False
typeName [] An array of elements of type typeName
map( A key value mapping where the key of type typeName is used
typeName1, to retrieve a value of type typeName2
typeName2)
void A type used to represent "no data"
idref A type used to represent a reference to a specific object, e.g.
class instance. The form of classNameIdref is used to reference
objects that instantiate the class className, e.g. contractIdref
refers to objects that instantiate the contract class.
4.2 Namespace prefixes
Table 3 below shows the namespace prefixes for the MPEG-21 CEL/MCO standards and other related
schemas together with their references.
Table 3 — Mapping of prefixes to namespaces for the MPEG-21 CEL/MCO standards and other
related schemas
Prefix Corresponding namespace References
[1]
dc https:// purl .org/ dc/ elements/ 1 .1/ ISO 15836
[2]
dii u r n : mp e g : mp e g 21: 20 02: 01 -DI I -NS # ISO/IEC 21000-3
[3]
vcard http:// www .w3 .org/ 2006/ vcard/ ns # IETF RFC 2426
mvco https:// purl .oclc .org/ NET/ mvco .owl # ISO/IEC 21000-19
avco https:// purl .oclc .org/ NET/ aumvco .owl # ISO/IEC 21000-19/Amd1
cel-core u r n : mp e g : mp e g 21: c e l : c or e: 2015 # ISO/IEC 21000-20:2016
cel-ipre u r n : mp e g : mp e g 21: c e l : ipr e: 2015 # ISO/IEC 21000-20:2016
© ISO/IEC 2022 – All rights reserved

TTaabbllee 33 ((ccoonnttiinnueuedd))
Prefix Corresponding namespace References
cel-pane u r n : mp e g : mp e g 21: c e l : p a ne: 2015 # ISO/IEC 21000-20:2016
cel-rele u r n : mp e g : mp e g 21: c e l : r e le: 2015 # ISO/IEC 21000-20:2016
mco-core u r n : mp e g : mp e g 21: mc o: c or e: 2015 # ISO/IEC 21000-21:2017
mco-ipre u r n : mp e g : mp e g 21: mc o: ipr e: 2015 # ISO/IEC 21000-21:2017
mco-pane u r n : mp e g : mp e g 21: mc o: p a ne: 2015 # ISO/IEC 21000-21:2017
mco-rele u r n : mp e g : mp e g 21: mc o: r e le: 2015 # ISO/IEC 21000-21:2017
5 Overview
5.1 General aspects
MPEG-21 CEL/MCO schemas and ontologies can be used by music and media value chain stakeholders
to share and exchange, in an interoperable way, all metadata and contractual information connected
to creative works, leading to transparent payment of royalties and reduced time spent searching for
the right data. The latter is due to inference and reasoning capabilities inherently associated with
ontologies. That is, knowledge and data can be derived by evidence and logic based on rich semantic
copyright models expressed by MPEG-21 CEL/MCO schemas and ontologies. In this way, the data
derived are unambiguously interpretable, facilitating efficient processing in business-to-consumer
(B2C) and business-to-business (B2B) music and media value chains.
Furthermore, for contractual music and media asset trading, smart contracts can be used to encode
the terms and conditions of a contract. They validate contractual agreements between stakeholders
before a DLT value transfer is enabled. In other words, smart contracts could allow music and media
royalties to be administered almost instantaneously and manage usage allowances and restrictions.
Rather than passing through intermediaries, revenue from a stream or download could be distributed
automatically to rights holders, according to agreed terms and conditions (e.g. splits), as soon as an
asset is downloaded or streamed.
Therefore, the challenge is converting MPEG-21 CEL/MCO standardized schemas and ontologies to
smart contracts that can be executed on existing DLT environments, thus enriching DLT environments
with inference and reasoning capabilities inherently associated with ontologies. Note that this process
will increase trust among music and media value chain stakeholders for sharing data in the ecosystem
since the data will be cryptographically secured and verified on a DLT. By addressing this challenge in
a standard and agnostic way, with respect to smart contract languages and thus DLT environments,
it would also ensure that MPEG-21 CEL/MCO schemas and ontologies prevail as the interlingua for
[4]
transferring verified contractual data from one DLT to another .
5.2 Relationships between MPEG-21 CEL/MCO and DLTs
This subclause describes the relationships between MPEG-21 CEL/MCO elements and DLTs components,
for the conversion of MPEG-21 CEL/MCO contracts to smart contracts for media and vice versa. Smart
contracts for media are distinguished from generic smart contracts since they are the result of the
conversion process from a specific MPEG-21 CEL/MCO contract.
For the description of above-mentioned relationships, the main elements identified for MPEG-21 CEL/
MCO are the contract, the party, the IP entity, and the deontic expression. The counterparts in a DLT-
based scenario have been identified as shown in Table 4.
© ISO/IEC 2022 – All rights reserved

Table 4 — Relationships between MPEG-21 CEL/MCO elements and DLTs components
MPEG-21 CEL/MCO DLTs
Contract Smart contract for media
Party DLT address
IP entity Non-fungible token
Deontic expression Non-fungible token
Furthermore, in Figure 1, as for example, the relationships between MPEG-21 MCO and DLTs are
depicted, albeit similar relationships apply between MPEG-21 CEL and DLTs. These relationships are
further explained in the following.
© ISO/IEC 2022 – All rights reserved

a) ISO/IEC 21000-21:2017 Media Contract Ontology
b) Relationship between ISO/IEC 21000-21:2017 Media Contract Ontology and DLTs
Key
smart contract and/or token
DLT identity
text
refers to
Figure 1 — Relationships between MPEG-21 MCO elements and DLTs components
1) Contract – Smart contract for media: the MPEG-21 CEL/MCO contract element is the one that
includes or refers to the digitalized contractual information extracted from a narrative contract.
Whilst the smart contract for media is the result of the conversion process from the MPEG-21 CEL/
MCO contract. Thus, the counterpart of an instance of an MPEG-21 CEL/MCO contract is a unique
smart contract for media deployed on a specific DLT.
2) Party – DLT address: a Party element is the representation of the identity of a user or organization
bound by the narrative contract. Since identities in DLTs are represented through addresses, the
© ISO/IEC 2022 – All rights reserved

Party element counterpart is a DLT address. Thus, a Party identity represented by a DLT address
may also be authenticated in the DLT and referenced in a smart contract for media.
3) IP entity – Non-fungible token: an IP Entity element is the representation of an asset, and the
reference to this asset can be stored on a DLT. This representation of an asset may be serialized
according to the concept of non-fungible tokens. Thus, in smart contracts an IP Entity may be
represented by a token. Then, the entire set of information related to a specific IP Entity is linkable
to the associated token. Two reasons support this approach:
i) the linkage between IP Entities and related smart contracts for media is maintained at a high
level, particularly when DLTs offer append-only data storage and not a more complex one;
ii) it makes feasible the process of auditing, exploiting at best the immutability feature of DLTs;
the history of all operations executed over an IP Entity, indeed, can be found in one place.
4) Deontic expression – Non-fungible token: a Deontic Expression encompasses the properties of
an agreed machine-readable contract clause regulating the actions of the Parties (e.g. obligations,
permissions, and prohibitions). This representation of a clause may also be serialized according to
the concept of non-fungible tokens. The reasons for supporting this approach are:
i) it enables a unique way for storing clauses on DLTs, that is also beneficial in terms of
interoperability, for sharing these clauses with other DLT-based applications;
ii) it allows the transfer of value in the form of obligations, permissions and prohibitions, similarly
to how cryptocurrency transfers are done.
6 Bidirectional conversion between MPEG-21 CEL/MCO contracts and smart
contracts for media
This clause describes the bidirectional conversion processes between MPEG-21 CEL/MCO contracts
and smart contracts for media. In Figure 2 it is shown the forward conversion from MPEG-21 CEL/MCO
contracts to smart contracts for media, while, in Figure 3 it is shown the backward conversion from
smart contracts for media to MPEG-21 CEL/MCO contracts.
Both processes interact with several actors and DLTs where a smart contract for media would be
(forward conversion) or has been (backward conversion) deployed. In the following subclauses, a set
of interrelated components are described, each of which consists of a grouping of related functionality
encapsulated behind a well-defined interface (e.g. inputs and outputs).
The smart contract for media may store instances of the MPEG-21 CEL/MCO contract elements either:
— in data structures of the smart contract for media; or
— in non-fungible tokens referenced by the smart contract for media, which are stored on the same
DLT but managed through a different smart contract.
By storing these elements in that way, this document also facilitates the backward conversion from
[5] [6]
smart contracts for media to MPEG-21 CEL/MCO contracts in the XML /RDF form. In turn, MPEG-21
CEL/MCO contracts may be transformed into narrative contracts.
© ISO/IEC 2022 – All rights reserved

Figure 2 — Conversion workflow from MPEG-21 CEL/MCO contracts to smart contracts for
media
Figure 3 — Conversion workflow from smart contracts for media to MPEG-21 CEL/MCO
contracts
6.1 Conversion from MPEG-21 CEL/MCO contracts to smart contracts for media
The process of conversion from an MPEG-21 CEL/MCO contract to a smart contract for media involves
the execution of several components and the interaction with three actors and a DLT. This process is
graphically illustrated in Figure 2.
6.1.1 MPEG-21 CEL/MCO parser
The MPEG-21 CEL/MCO parser component gets as input an MPEG-21 CEL/MCO contract, provided
by an MPEG-21 CEL/MCO contract developer, and produces a set of media contractual objects. It is
expected that the MPEG-21 CEL/MCO contract has been checked to be syntactically and semantically
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valid. Otherwise, the validation result provided by the MPEG-21 CEL/MCO parser returns two levels of
information:
1. Errors: syntactic or semantic errors are identified.
2. Warnings: elements of information that may be lost during the conversion process.
Input:
— MPEG-21 CEL/MCO contract: it consists of XML/RDF documents containing one or several MPEG-
21 CEL/MCO elements that represent a contract.
Output:
— Media contractual objects: a structured set of information related to the deontic expressions,
actions, entities, and constraints extracted from an MPEG-21 CEL/MCO contract.
These media contractual objects are only dependent upon the MPEG-21 CEL/MCO standards and as
such are agnostic with respect to any specific DLT.
6.1.2 Smart contract generator
The smart contract generator component produces a smart contract specification by combining
information related to an MPEG-21 CEL/MCO contract in the form of media contractual objects with
some specific smart contracts templates. This component is meant to be dependent on the smart
contract language.
Inputs:
— Media contractual objects: a set of media contractual objects is needed to define the information
that is contained in the smart contract for media.
— Smart contract templates: the DLT smart contract developer (e.g. the person skilled in the specific
DLT smart contract language) elaborates a set of specific smart contract templates to be utilized in
the conversion process.
Output:
— Smart contract specification: a set of elements that represent the information needed by the DLT
tokens and payments manager component to deploy the smart contract for media.
This smart contract specification includes information produced based on the objects found while
traversing the set of media contractual objects. If MPEG-21 CEL/MCO obligations including payments
are found, then the smart contract generator produces the information needed for creating revenue
functions for each party involved. For instance, if a party is obliged to share its revenue with another
party, then a smart contract method performs the revenue sharing function (e.g. royalties flow).
Moreover, for each MPEG-21 CEL/MCO deontic expression and IP entity found in the media contractual
objects, the smart contract generator produces the information needed for creating a new non-fungible
token.
6.1.3 DLT tokens and payments manager
The purpose of the DLT tokens and payments manager component is to deploy the sma
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