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					 Semantic Digital Rights Management for
 Controlled P2P RDF Metadata Diffusion

                          Roberto Garcia, Ph. D (1)
                        Giovanni Tummarello, Ph. D (2)

    (1) GRIHO – Human-Computer Interaction Research Group
               Universitat de Lleida, Spain

    (2) SEMEDIA – Semantic Web and Multimedia Group, Università
                    Politecnica delle Marche, Italy

                                                            Research Group on
         SEMEDIA                                            Human Computer
          Semantic Web and                                  Interaction and
                Multimedia                                  Databases
Scenario: P2P exchange of RDF information

 Information is a “resource” itself, exchanged
  like in file sharing applications
 A client might become a server at a later time
 Information is expressed in RDF, strictly based
  on the W3C RDF Semantics specifications [1]
    (important! It would be much simpler otherwise ;-) )

[1] RDF Semantics - W3C Recommendation 10 February 2004
Example: DBin (1)
Example: DBin (2)
         Interconnected communities
Users can join multiple groups:
 theyacquire knowledge to
 perform cross concerning
 The diffuse information across
 groups which are interested in
 the same resources (e.g.
 Madonna as a singer, Madonna
 as an actress.. A new pic is
 relevant to both)

          Seems   a wonderfully new, open scenario
          But restrictions are needed in some cases!
    Idea: I’ll tell you if you sign this agreement

 Deterministically derive HASHES for parts of the
  RDF Graph
 Use Semantic Digital Right Management
  ontology to specify the policy and an OWL
  reasoner to verify
 Give out the information if the other party agrees
  to put his/her digital signature on the RDF
  reppresentation of the

             POLICY +Information HASH
Minimum Self-contained Graph (MSG)

Involves (Def) :An RDF statement involves a name if it has that name
     as subject or object.

MSG (Def). Given an RDF statement s, the Minimum Self-contained
   Graph (MSG) containing that statement, written MSG(s), is the set
   of RDF statements comprised of the following:
  The statement in question;
  Recursively, for all the blank nodes involved by statements
   included in the description so far, the MSG of all the statements
   involving such blank nodes;
MSG surrounding a URI: example

                  MSG(statement) (approx
                  def). The “blank node closure”
                  of the statement.
     MSG decomposition of RDF Graphs

   Theorem 1. If s and t are distinct statements and t belong to
    MSG(s), then MSG(t) = MSG(s).
   Theorem 2. Each statement belongs to one and only one MSG.
   Corollary 1. An RDF model has a unique decomposition in MSGs.
MSG decomposition of a graph: example
    Deterministic, content based Identifiers for MSGs

    MSGs are perfectly valid, standalone RDF graphs.

    As such they can be processed with algorithms such as canonical serialization.
     [Carrol 2004]

    The canonically serialized MSG is a binary file, as such it can be hashed

    Given an hash function with appropriate characteristics, the resulting hash value
     forms a deterministic, content based identifier for the MSG itself

    remote peers derive the same ID for the same MSG in their DB.

    Sets of such IDs are used to identify the information covered in the
    RDF graph decomposition and identifiers

Graph MSGID list = Sort (MSG ID 1 , MSG ID 2, ..)
Graph ID= Hash(MSGID)

                                              MSG ID = MD5(Canonical(MSG))
                                                     = 45FA76B61FC0
    RDF/MSG decomposition applications (1)
   a graph can be incrementally and differentially (!)
    transferred between two parties one MSG at a time.
   Distributed P2P scenario : RDFGrowth Algorithm [1]
   1 to 1 efficient Syncronization: RDFSync Algorithm (new!)

                                        RDFSync algorithm
                                        Traffic VS delta changes

                                        [1] G. Tummarello, C. Morbidoni, J. Petersson, F.
                                        Piazza, M. Mazzieri, P. Puliti, "Toward widely
                                        deployable Semantic Web P2P: tools, definitions
                                        and the RDFGrowth algorithm", Workshop on
                                        Semantic Web Technology for Mobile and
                                        Ubiquitous Applications at ISWC 2004, November
                                        2004, Hiroshima, Japan.
   RDF/MSG decomposition applications (2)
         Signing a Minimum Selfcontained Graph (MSG)

                                           IdKtR...j4c=                    mbz:artistid=15290


                                                                   mus:plays                    rdf:type


                                                     mus:Band                  MD5:123123

G. Tummarello, C. Morbidoni, P. Puliti, F. Piazza, "Signing individual fragments of an RDF graph", 14th
    International World Wide Web Conference WWW2005, Poster track, May 2005, Chiba, Japan
 RDF/MSG decomposition applications (3)

 This paper! 
 A procedure to serve information in RDF
  subject to a previous agreement on the
  use of that very information
             The exchange procedure
A client R requests information from a server S

   R makes a request to S.

   S receives the request, creates the RDF for the answer, calculates its MSG IDs and uses
    them in a new RDF file which defines its usege restrictions (see later). Sends this new
    RDF, from here on called proposal, to R.
    Optionally: signs the proposal so to provide S with the guarantee that if agreed, the answer
    will actually be provided within the specified terms

   R receives the proposal and, if it agrees to the terms, signs it and returns it to S.
    Optionally: thanks to the properties of MSGs, R can check if the answer correspond to
    information which is already locally known. In this case R could drop the request as not
    interesting, or proceed, e.g., in case it is important for R to prove that the information was
    in fact legally acquired.

   S receives the signed proposal, stores it and replies with the answer computed in 2).
    Optionally: the signed proposal might be countersigned to allow R to prove that the
    information was obtained by legal means.
       Semantic Digital Rights Management to
             define usage restrictions
    ISO/IEC MPEG-21: about DRM on multimedia
    components: Rights Expression Language (REL) which
     uses terms explained in the Rights Data Dictionary
    Lack of formal semantics!
           the Copyright Ontology (OWL DL based) [1]
    As it deals with Reproduction rights and it is in OWL , fits
     great with this our purpose!

[1] García, R.: "A Semantic Web Approach to Digital Rights Management". PhD Thesis, Technologies
Department, Universitat Pompeu Fabra, Barcelona, ES, 2006.
An example licence instance
                                    P2PDiff                       2005-11-20
    urn:p2p:granter     agent                    pointInTIme
                                     Agree                        T13:15+01

    urn:p2p:granted        agent

    urn:p2p:granted    agent        P2PDiff      theme
      2006-01-01                                  origin
                       start                                   urn:p2p:peerA
         P6M          duration                 recipient       urn:p2p:peerB
                                 condition          0..2

       rdf:value 3                  P2PDiff
       currency €                   Transfer
                      Licences are classes
     urn:p2p:granted   agent         recipient urn:p2p:granter
 To check an action: create an instance and use a DL classifier!
   A simple applications of RDF decomposition

   OWL based copyright ontology fits the task and stays in
    the domain of Semantic Web Tools

   To make it into a “legally binding” exchange mechanism,
    specific laws might be needed
              Thanks for your attention
                                  Research Group on
         SEMEDIA                  Human Computer
                                  Interaction and
Semantic Web and Multimedia

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