Semantic Representation and Enforcement of Electronic Contracts on Audiovisual Content
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Semantic Representation and Enforcement of Electronic Contracts on Audiovisual Content by V´ıctor Rodr´ıguez Doncel Submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy Universitat Polit`ecnica de Catalunya Department d’Arquitectura de Computadors Advisor: Dr. Jaime Delgado Merc´e Barcelona, February 2010 ii Abstract This Thesis presents a computer representation language for agreements on multimedia content and the mechanisms to exe- cute the agreements in the framework of a content distribution system. The presented model is able to represent complex clause terms and can be interpreted by logic reasoners. This work is assumed to be in the wider context of a multimedia distribution system, and it has been integrated with other elements defined in the international standard ISO/IEC 21000. This Thesis presents a computer representation language for agreements on multimedia content and the mechanisms to execute them in the frame- work of a content distribution system. Content distribution systems trade audiovisual material in exchange of economic compensation in a framework of secure transactions between iden- tified users, what is generally known as Digital Rights Management (DRM) systems. Some DRM platforms have been deployed by private initiatives fol- lowing closed specifications not intended to interoperate with other systems and not conforming to the standards. Some other initiatives, resulted from the cooperation of corporations and universities in consortia have chosen open design solutions and even open implementations to deploy the content exchange systems. One of the most notable frameworks for the creation, protection, distribution and rendering of multimedia content has been that of MPEG (Moving Pictures Experts Group), whose specification is open, has partial code availability and it has been sanctioned as a collection of International Standards promulgated by the International Organization for Standardization (ISO) with worldwide effect. Nevertheless, neither the MPEG framework -which is the reference plat- form taken for this work- nor the other existing DRM systems handle consis- tently the complete intellectual property value chain and they tend to focus almost exclusively on distributor to consumer transactions. Consequently, iii iv the DRM platforms express the transactions agreements with language el- ements enough to represent well end user licenses but only these. These digital licenses are written in the so called Rights Expressions Languages (REL), well defined XML documents, from which the MPEG-21 REL is a paradigm and the reference of this Thesis. REL licenses are issued by the right owners of the intellectual property protected material to authorise the execution of a certain action by a certain user, who in exchange has pos- sibly paid an amount of money called fee. These authorised actions result almost always in the rendering operation, which is the most common task for an end user or consumer. However, some intermediate operations are needed to achieve the final product, operations which start with the work conception -from an intellectual property point of view- and continue pos- sibly with adaptations, performances, productions and editions before the final product is broadcasted or distributed. These operations are executed by different actors exchanging also content in economical transactions regu- lated in narrative contracts and which so far have been somewhat neglected by the existing RELs. It is a position of this work that the MPEG-21 REL can be used to repre- sent and enforce the agreements of these transactions if the language is prop- erly extended or even substituted with a new semantic representation. For this regard, it is fundamental the analysis of the intellectual property value chain and its most precise description. The intellectual property value chain is described with the Media Value Chain Ontology proposed in the Thesis, a representation in OWL (Ontology Web Language) of the workflow of mul- timedia content and the successive transfers of intellectual property. Based on the international consensus on intellectual property, the Media Value Chain Ontology describes the different kinds of intellectual property objects (original works, manifestations, instances etc.), the different acknowledged roles intervening in the process (creator, distributor etc.), and the different actions relevant to the intellectual property (both a public communication and a marketing campaign may be relevant in the commercial process but only the first regarding the intellectual property). It also covers the precise relations between these entities, and it provides as well the mechanisms to represent authorisations and bans. The formalization of the model under the terms of Description Logics allows performing reasoning operations and the implementation of advanced authorisation mechanisms of the licenses expressed with the ontology. This Thesis proposes the conversion of narrative contracts (contracts written in plain English) in the audiovisual market to the format of digital licenses. This conversion, on despite of the unavoidable loose of informa- v tion, may be of interests if as a result of it, the transaction can take place in the digital environment and governed by the derived digital license. This is achieved by means of a rich knowledge representation schema, where the obligations and permissions exchanged in a contract are dealt as expressions of the deontic logic, and they can determine the behaviour of the distribu- tion platform. A semantic authoriser is proposed which is able to execute rules, evaluate the conditions and the context and give the proper response. To minimize the loose of information, the non enforceable contract clauses are structured into a standard electronic format called eContracts. This eContracts format, neutral regarding the contract theme, is enriched with the elements of the Media Value Chain Ontology to provide an adequate representation. The representation of the value chain proposed here, as well as the con- version from contracts to licenses, has been a part of different projects and has worked tightly integrated with other elements of wider Digital Rights Management systems. In practice, and in order to easily access to the on- tology features, an API (Application Programming Interface) in Java is also proposed. On top of it, several applications have been developed. The most paradigmatic acts as a server, and being located in a remote server it is able to receive registration requests and resolve queries intelligently. Users request their registration in the ontology server, which automati- cally maps their unique identifier to an instance of the ontology. But users also request the registration of their intellectual property objects, and the permissions they declare, which are also stored in the ontology as new class instances. With all this information and the basis knowledge in the model, the ontology server is able to resolve queries. These queries serve the different elements in the DRM architecture to validate their intellectual property operations. For example, the ontology server is able to answer which legal nature has a given resource, who is the rights owner of the resource, which is its provenance (the provenance being the intellectual property object from which it derives), which actions are allowed, etc. The representation of the value chain presented in this Thesis is a com- plete work but its applications can still be further developed. The authori- sation mechanisms can be put in practice with more complex rules, taking advantage of the interoperability of the Semantic Web data. vi Contents 1 Introduction 1 1.1 Aimsandobjectives ....................... 1 1.2 Methodology ........................... 3 1.3 Thesisoutline........................... 4 I State of the Art and Legal Framework 5 2 Legal Framework 7 2.0.1 International treaties on Intellectual Property . 7 2.0.2 Legal Framework on Intellectual Property . 9 2.0.3 Features of the Intellectual Property Law . 10 3 Knowledge representation towards reasoning 13 3.1 Logicsystems........................... 15 3.1.1 PropositionalLogic. 15 3.1.2 FirstOrderPredicateLogic . 17 3.1.3 ModalLogic ....................... 21 3.2 DescriptionLogics . 22 3.2.1 DescriptionLogicsemantics . 23 3.3 TheSemanticWeb ........................ 26 3.3.1 TheSemanticWebvision . 26 3.3.2 The Semantic Web technologies . 28 3.4 PracticaluseofOntologies. 44 4 Contract representation 47 4.1 Digital Representation of Contracts . 47 4.1.1 Objectives of a contract representation . 47 4.1.2 A sample audiovisual contract . 49 4.1.3 Overview of digital representations of contracts . 52 vii viii CONTENTS 4.1.4 Contracts Expression Language . 53 4.1.5 OASISeContracts . 55 4.2 Value Chain Representations . 56 4.2.1 Functional Requirements for Bibliographic Records . 57 4.2.2 Conceptual Reference Model and others . 61 5 Rights Expression Languages in DRM systems 63 5.1 DRMSystems........................... 63 5.1.1 OverviewofsomeDRMsystems . 64 5.1.2 Common elements in DRM systems . 71 5.2 MPEG-21 as a Framework for DRM Systems . 73 5.2.1 OverviewofMPEG-21 . 73 5.2.2 MXM as a MPEG-21 implementation . 76 5.3 Right Expression Languages . 81 5.3.1 MPEG21REL ..................... 81 5.3.2 ODRL........................... 86 5.3.3 OtherRELlanguages . 87 5.3.4 SemanticRELs ...................... 94 II Contribution 97 6 The Media Value Chain Ontology 99 6.1 Industrial Value Chain and Intellectual Value Chain