Enabling interoperable and rights-aware DRM using the Semantic Web
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Enabling interoperable and rights-aware DRM using the Semantic Web

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This presentation, which was carried out at the DRM track of SmartUniversity'07, presents a Semantic Web approach to Digital Rights Management. This approach is based on a Copyright Ontology, ...

This presentation, which was carried out at the DRM track of SmartUniversity'07, presents a Semantic Web approach to Digital Rights Management. This approach is based on a Copyright Ontology, implemented using OWL and DL reasoning.

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    Enabling interoperable and rights-aware DRM using the Semantic Web Enabling interoperable and rights-aware DRM using the Semantic Web Presentation Transcript

    • Enabling interoperable and rights-aware DRM using the Semantic Web Roberto García [email_address] Universitat de Lleida, Spain September 20, 2007 Sophia Antipolis, France
    • Where did you say you come from? Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Table of Contents
      • Introduction
        • Semantic Web
      • Objectives
      • Specification
      • Conceptualisation
      • Implementation
      • Evaluation
      • Conclusions
      • Future Work
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Introduction
      • Digital media: easy production and copy
      • Digital Rights Management (DRM)
      • Windows Media DRM, iTunes FairPlay, RealNetworks Helix, Sony MagicGate…
      DRM copy play … Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Introduction
      • Internet: easy distribution
      • DRM interoperability
      REL Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 DRM DRM DRM
    • Introduction
      • Need for a standard REL (Rights Expression Language)
      • Some efforts:
        • XML-based RELs
          • Formal syntax XML Schema for standard grammar
          • Informal semantics Rights Data Dictionaries
        • Creative Commons simple predefined licenses
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
      • XML-based RELs:
        • Limited expressivity
        • No interoperability mechanisms
        • Informal semantics, re-implement for each tool
      • Creative Commons:
        • Predefined and closed set of licenses
        • Non-commercial purposes
      Introduction Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Introduction
      • DRM Watch: “2005 Year in Review: DRM Standards” 1
        • “… consumer complaints have moved beyond overly restrictive DRMs to lack of interoperability among them…”
        • “… we see no production implementations …”
        • “… ContentGuards asserts its patents apply to any REL implementation in DRM…”
      • Electronic Frontier Foundation 2
        • “… fail to accommodate… copyright regimes.”
      1 http://www.drmwatch.com 2 http://www.eff.org Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Introduction
      • DRM standardisation difficulties
        • Internet/Web open and heterogeneous
        • Copyright complex domain
        • High level of abstraction (not bits or pixels)
      • Concentrate on the roots, formalise SEMANTICS
      ODRL “ Duplicate ” Reproduction Right Copy MPEG-21 “ Adapt ” CC “ Reproduction ” Copyright Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Introduction
      • Why semantics are needed?
      • Common scenario : web search and language ambiguity
        • Computers get confused because… …though we “see”:
        • " Smart University " (3rd edition) is an educational program dedicated to advanced technologies of Smart Card, e-ID, . ..
        • SMART (Sisterhood Mobilized for AIDS/HIV Research and Treatment) was founded in 1998...
        • SMART University welcomes all women infected or affected by HIV/AIDS who...
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Semantic Web
    • Introduction
      • Computers “see”:
        •  Smart University   
        • 
        • SMART University 
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Semantic Web
    • Introduction
      • XML allows some degree of automation
        • Data Interface: set of specific tags and grammar ( DTD , XMLSchem a)
          • < music >
          • < album format=“ mp3 ”>
          • < author type=“ group ”>Faithless</ author >
          • < title >Insomnia</ title >
          • ...
          • </ album >
          • </ music >
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Semantic Web
    • Introduction
      • With XML computers “see”:
          • < music >
          • < album format=“ mp3 ”>
          • < author type=“ group ”>  </ author >
          • < title >  </ title >
          • ...
          • </ album >
          • </ music >
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Semantic Web
    • Introduction
      • Interoperability problem
      • Global agreement required
        • Just formal syntax, no semantic interoperability tools
        • < music >
        • < album format=“ mp3 ”>
        • < author tipo=“ group ”> ...</ author >
        • < title >...</ title >
        • ...
        • </ album >
        • </ music >
      < song > < group >...</ group > < title >...</ title > < album >...</ album > <file>...</file> ... </ song > ? Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Semantic Web
    • Introduction
      • If the previous tool is presented a piece of data based on a new schema:
        • < song >
        • < group >Garbage</ group >
        • < title >Version 2.0</ title >
        • < album >Version 2.0</ album >
        • <file>...</file>
        • ...
        • </ song >
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Semantic Web
    • Introduction
      • That tool “sees”:
          • <  >
          • <  >  </  >
          • <  >    </  >
          • <  >    </  >
          • <  >...</  >
          • ...
          • </  >
      • Code interoperability rules case by case
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Semantic Web
    • Introduction
      • Semantic Web proposal
        • Web + Knowledge Representation
        • Web wide formal semantics
      • RDF : semantic net, graph model
      • RDF Schema : classes, inheritance,…
      • Web Ontology Language (OWL)
        • OWL-DL : scalable (decidable and tractable)
      • Semantic Web Rules
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Semantic Web
    • Introduction
      • RDF provides graph model:
      • Graph can model:
        • trees (XML)
        • tables (DBs)
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Semantic Web
    • Introduction
      • RDFSchema : OOP-like primitives
        • type
        • class, property
        • subclass, subproperty
        • domain, range
      Song Class Audio Class subClassOf http:// music .org / song1 type title Property attribute Property subPropertyOf Literal Class “ ...” title type domain range RDFSchema RDF type Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Semantic Web
    • Introduction
      • Web Ontology Language (OWL)
        • Logic reasoning
        • Primitives for semantic interoperability
          • Equivalent classes and properties equivalentClass , equivalentProperty
          • Disjoint classes disjointWith
          • Inverse, transitive, symmetric properties inverseOf , TransitiveProperty , SymmetricProperty
          • Cardinality maxCardinality , minCardinality
          • Unique value properties FunctionalProperty
          • Identificative properties InverseFunctionalProperty
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Semantic Web
    • Table of Contents
      • Introduction
      • Objectives
      • Specification
      • Conceptualisation
      • Implementation
      • Evaluation
      • Conclusions
      • Future Work
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Objectives
      • Semantic Web approach to DRM:
        • Knowledge Representation tools
        • Web Wide applicability
      • Benefits:
        • Formalise semantics
        • Facilitate interoperability and implementation
        • Overcome REL patent ?
        • Include copyright
        • Support full value chain
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Objectives
      • Ontology development based on Methontology :
        • Specification
        • Conceptualisation (and formalisation)
        • Implementation
        • Evaluation
      • XML Semantics Reuse
        • Profit from existing XML Schema based RELs
        • Formalise implicit semantics
        • XML Schema to Web Ontology
        • XML data to semantic data (RDF)
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Table of Contents
      • Introduction
      • Objectives
      • Specification
      • Conceptualisation
      • Implementation
      • Evaluation
      • Conclusions
      • Future Work
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Specification
      • Copyright domain analysis
      • Generic Ontology
        • WIPO 1 worldwide harmonisation
      • Literary, artistic and scientific works (not ideas)
      • Maybe derived, but always original
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 1 World Intellectual Property Organisation Copyright Treaty, 1996
    • Specification Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Specification
      • Applicable to the
        • “ Controlled P2P metadata diffusion scenario”
      Peer A Peer B <rdf:RDF> <rdf:RDF> <rdf:RDF> <rdf:RDF> Make Available Right <rdf:RDF> Reproduction Right Scenario Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Table of Contents
      • Introduction
      • Objectives
      • Specification
      • Conceptualisation
        • Creation, Rights and Action Model
      • Implementation
      • Evaluation
      • Conclusions
      • Future Work
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Conceptualisation
      • Complex domain, build model in three steps:
        • Creation Model
        • Rights Model
        • Action Model
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Conceptualisation Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Victor Hugo’s Les Misérables Creation Model
    • Conceptualisation
      • Work
        • “ Mozart's The Magic Flute”. ISWC
      • Manifestation
        • “ The printed scores”. ISBN
      • Performance
        • “ A scenic play”.
      • Fixation
        • “ A sound recording”. ISRC
      • Communication
        • “ An Internet stream”.
      • Instance
        • “ A CD”. UPC
      •  has Derivation ┙
      •  has Manifestation ┙
      •  has Performance ┙
      •  ha sFixation ┙
      •  ha sCommunication ┙
      •  ha sInstance ┙
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Creation Model
    • Conceptualisation Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Rights Model
      • End-users do not hold rights
        • Usage licenses
        • Special permissions:
          • Quotation
          • Education
          • Information
          • Official Act
          • Private Copy
          • Parody
          • Temporary Reproduction
      Conceptualisation Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Rights Model
      • Actions, the building blocks
      Conceptualisation Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Action Model
      • Actions governed by Economic Rights:
        • Reproduction Right : copy
        • Distribution Right : distribute; sell, rent, lend
        • Public Performance Right : perform
        • Fixation Right : record
        • Communication Right : communicate; retransmit, broadcast, make available
        • Transformation Right : transform; adapt, translate
      Conceptualisation Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Action Model
    • Conceptualisation
      • End-user actions, to use a…
        • manifestation: buy
        • instance: buy
        • performance: attend
        • communication: access
          • broadcast: tune
          • something made available: access
      • picture, sculpture
      • book, CD, DVD
      • projection, recital, exhibition
      • TV channel, radio station
      • web page, stream
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Action Model
      • Altogether: model copyright value chains
        • E.g. “serials adapted from literary works”
      Conceptualisation Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Action Model
      • Actions for users’ special permissions:
        • Quotation Right : quote , limited extent copy , usually requiring an attribute action
        • Private Copy Right : copy producing a reproduction for private consumption
        • Education Right : educational act , any copy , communicate or perform with educational or research purposes
        • Temporary Reproduction Right : a copy that produces a temporal reproduction
      Conceptualisation Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Action Model
      • Case roles (linguistics): relate actions to involved entities
      Conceptualisation Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Action Model
      • License building primitives:
        • Event Patterns : to state what is obliged, permitted or prohibited
          • Built from actions and case roles
      Conceptualisation Scenario All copy events performed by agent “ granted ” who copies “ content01 ” from “ PeerA ” to two peers from the set “ PeerB, PeerC, PeerD ” at any time point six months after “ 2007-06-01 ” Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Action Model
      • License building primitives:
        • Agree : model permissions
          • theme points to the permitted event pattern
      Conceptualisation Scenario Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Action Model
      • License building primitives:
        • consequence : model obligations
          • Points to the obliged event pattern
      Conceptualisation Scenario Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Action Model
      • License building primitives:
        • condition : model a priori conditions
          • Points to the condition event pattern
        • Disagree : model prohibitions
          • theme points to the prohibited event pattern
        • Other concepts:
          • Transfer: model interchanges, commercial or not.
          • Time
          • Location
          • ...
      Conceptualisation Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Action Model
      • Rules, examples:
        • First sale exhaustion: ∀ s:Sell, ∀ i:Instance theme(s,i) -> ¬ ∃ s’:Sell theme(s’,i) ∧ s≠s’
        • Assign author rights on Manifest:
      Conceptualisation Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Action Model
    • Table of Contents
      • Introduction
      • Objectives
      • Specification
      • Conceptualisation
      • Implementation
      • Evaluation
      • Conclusions
      • Future Work
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Implementation
      • One conceptual model, many implementations
      • Semantic Web implementation with OWL
      • OWL-DL variant
        • enables tractable and decidable reasoning for use-license checking, scalability
      • Additionally, Semantic Web rules
      OWL Full OWL DL OWL Lite + expressivity - complexity Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Implementation
      • Rights and License Patterns implemented as Classes
        • Copyright, Reproduction Right, Copy, CopyPattern,...
      • Uses implemented as Instances
        • u
      • if u ∈ Copy Pattern then license pattern authorises u
      Reproduction Right Copy Copyright Copy Pattern u ? Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Implementation
      • License Pattern Class built from constraints on kind of actions, agents, time points, locations, etc.
      • OWL Building Blocks
        • Classes for actions (e.g. Copy)
        • Logical operators (AND, OR, NOT)
        • OWL Restrictions , constraints on case roles (e.g. agent all values from PublisherSubscribers)
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Implementation
      • Copy pattern restricted to:
        • digital object ( theme )
        • group of users ( agent )
      • or
        • non-commercial ( aim )
      • depending on
        • time range ( pointInTime )
      Scenario Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Implementation
      • Description Logic notation for the commercial copy pattern:
        • Pattern ≡ Copy ⊓ ∀ pointInTime .≥ 2007-01-01,≤ 2007-06-30 ⊓ ∀ agen t.PublisherSubscribers ⊓ (≥ 1 agent ) ⊓ ∃ theme .{urn:doi.10.1032/…} ⊓ (≤ 1 theme )
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Implementation
      • Patterns permitted by Agree actions and prohibited by Disagree ones.
      • Algorithm:
        • If disagreed  not allowed
        • If agreed and not disagreed  allowed
        • If not agreed  not allowed
      • Disagree precedence allows:
        • Revocation
        • More complex patterns
        • Avoid DL reasoners limitations (details Annex A)
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Implementation Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Copy all copy actions Pattern 2 Pattern 2’ Allowed Pattern 1 Agree Disagree Agree
    • Implementation
      • OWL-DL reasoners services:
        • Satisfiability : consistency, license verification
        • Subsumption : compute subclasses
          • License interactions
          • License search
        • Instance Checking : class an individual belongs to
          • Check uses against licenses
        • Other:
          • Debugging , justifications for conclusions
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007 Pattern A Pattern B Pattern Use
    • Implementation
      • OWL-DL limitations:
        • No explicit variables
        • Difficult to model rules (if … then …)
      • Semantic Web rules
        • Variables
        • Classical rules
        • Built-ins (math, comparisons, date/time ops,...)
        • Integrates OWL
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Table of Contents
      • Introduction
      • Objectives
      • Specification
      • Conceptualisation
      • Implementation
      • Evaluation
      • Conclusions
      • Future Work
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Evaluation
      • Map MPEG-21 and ODRL ontologies to Copyright Ontology
        • Based on XML Semantics Reuse Methodology
          • XML Schemas  OWL Ontologies
          • XML instances  RDF metadata
      • MPEG-21, ISO/IEC 21000
        • Part 5 – REL, XML Schemas:
          • Core  RELOnto-R
          • Standard Extensions  RELOnto-SX
          • Multimedia Extensions  RELOnto-MX
        • Part 6 – RDD, informal ontology  RDDOnto
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Evaluation
      • ODRL 1.1 (OMA V1.0 DRM REL)
        • XML Schemas:
          • Expression Language  ODRLOnto-EX
          • Data Dictionary  ODRLOnto-DD
      • Benefits
        • Check Copyright Ontology coverage
        • Apply semantic tools existing RELs
          • Validate MPEG-21 RDD standard
          • Implement Data Dictionary inheritance
          • License checking
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Evaluation
      • Build SemDRMS Semantic Digital Rights Management System
        • Controlled P2P metadata diffusion
      Peer A SemDRM copy make available Licenses Store DL Reasoner Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Evaluation
      • Digital Media Project (DMP)
        • Traditional Rights and Usages informal descriptions, difficult to incorporate into DRM systems
          • Quote
          • Private Copy
          • Time Shift
          • ...
      • Copyright Ontology: profit from copyright model and capture rights exceptions
        • No enforcing mechanisms, accountability
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Evaluation
      • Quote scenario
        • Right exception model:
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Evaluation
      • Concrete quote action:
        • Tim wants to quote 10 seconds of a work by John
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Evaluation
      • Checking:
      • Result:
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Evaluation
      • Private Copy scenario
        • Right exception model:
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Evaluation
      • Concrete private copy action:
        • Peter wants to produce a personal copy of “My best quote of the year”
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Evaluation
      • Checking:
      • Result
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Table of Contents
      • Introduction
      • Objectives
      • Specification
      • Conceptualisation
      • Implementation
      • Evaluation
      • Conclusions
      • Future Work
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Conclusions
      • Concentrate on semantics
      • Ontology , more expressivity
      • Include copyright
      • Facilitate implementation and interoperability
        • Reuse DL reasoners for license checking
        • RELs ontologies, XML Semantics Reuse
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Table of Contents
      • Introduction
      • Objectives
      • Specification
      • Conceptualisation
      • Implementation
      • Evaluation
      • Conclusions
      • Future Work
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Future Work
      • Full SemDRMS based on OWL-DL Copyright Ontology
      • Complete Mappings to Copyright Ontology
        • MPEG-21 REL Ontologies
        • ODRL Ontologies
        • Creative Commons
      • Security and trust through RDF signatures
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • More details: http://rhizomik.net/ontologies/copyrightonto http://rhizomik.net/semdrms http://rhizomik.net/~roberto/thesis Smart University DRM, from research to implementations Thank you for your attention Roberto García [email_address] Universitat de Lleida, Spain
    • Smart University DRM, from research to implementations Annex A Implementation Details How to deal with licenses using Description Logic reasoners
    • Implementation
      • Pattern ⊑ Copy
      • Pattern ≡ ∀ pointInTime.≥ 2006-01-01, ≤ 2006-06-30 ⊓ ∃ agent.{granted} ⊓ ∃ origin.{peerA} ⊓ ∃ theme.{fragment01} ⊓ (≤ 2 recipient) ⊓ ∀ recipient.{peerB, peerC, peerD}
      Scenario Agree Problem Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Implementation
      • Problem : Open World Assumption (OWA)
      • OWA sensible constructs:
        • m ax Cardinality (≤ n): new facts can make cardinality ≥ n
        • allValuesFrom ( ∀ R.C): new facts where R.(¬C)
      • OWA insensible constructs:
        • m in Cardinality (≥ n): once ≥ n, new facts cannot make cardinality ≤ n
        • someValuesFrom ( ∃ R.C): once R.C, new facts cannot make ¬( ∃ R.C)
      0 1 3 2 maxCardinality 2 (n ≤ 2) minCardinality 3 (n ≥ 3) New facts “ OPEN WORLD” Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Implementation
      • Metalevel negation to overcome OWA
      • Agree OWA insensible constructs
        • ∃ , ≥,…
      • Disagree “negated” OWL sensible constructs
        • ∀ R.C  ∃ R.¬C
        • ≤ n  ≥ n+1
      • Allowed(u)  Agree.theme(u) ⊓ ¬Disagree.theme(u)
      Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Implementation
      • Pattern’ ⊑ Copy
      • Pattern’ ≡ ∀ pointInTime.≥ 2006-01-01, ≤ 2006-06-30 ⊓ ∃ agent.{granted} ⊓ ∃ origin.{peerA} ⊓ ∃ theme.{fragment0001}
      • Pattern’’ ≡ Pattern’ ⊓ ( ( ≥ 3 recipient) ⊔ ∃ recipient.( ¬ {peerC, peerD, peerB}) )
      Scenario Agree Disagree Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007
    • Implementation Scenario [ a Copy; agent :granted; origin :peerA; theme :fragment02 ; recipient :peerB ] [ a Copy; agent :granted; origin :peerA; theme :fragment01; recipient :peerC, :peerD ] [ a Copy; agent :granted; origin :peerA; theme :fragment01; recipient :peerB , :peerC, :peer E ] Allowed Copy Pattern ’ Pattern’’ Enabling interoperable and rights-aware DRM using the Semantic Web – © Roberto García 2007