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Semantic Digital Rights Management for
Controlled P2P RDF Metadata Diffusion
Roberto Garcia, Ph. D (1)Giovanni Tummarello, Ph. D (2)
SEMEDIASemantic Web and
Multimedia http://semedia.deit.univpm.it
(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 Human Computer Interaction and Databases
Scenario: P2P exchange of RDF informationScenario: P2P exchange of RDF information
Information is a “resource” itself, exchanged Information is a “resource” itself, exchanged like in file sharing applicationslike in file sharing applications
A client might become a server at a later timeA client might become a server at a later time Information is expressed in RDF, strictly based Information is expressed in RDF, strictly based
on the W3C RDF Semantics specifications [1] on the W3C RDF Semantics specifications [1] (important! It would be much simpler otherwise ;-) )(important! It would be much simpler otherwise ;-) )
[1] RDF Semantics - W3C Recommendation 10 February 2004 [1] RDF Semantics - W3C Recommendation 10 February 2004
http://www.w3.org/TR/rdf-mt/http://www.w3.org/TR/rdf-mt/
Example: DBin (1) Example: DBin (1)
Example: DBin (2) Example: DBin (2)
Interconnected communitiesInterconnected communities
Users can join multiple groups:Users can join multiple groups:
they acquire knowledge to they acquire knowledge to perform cross concerning perform cross concerning queriesqueries
The diffuse information across The diffuse information across groups which are interested in groups which are interested in the same resources (e.g. the same resources (e.g. Madonna as a singer, Madonna Madonna as a singer, Madonna as an actress.. A new pic is as an actress.. A new pic is relevant to both)relevant to both)
Seems a wonderfully new, open scenario Seems a wonderfully new, open scenario But restrictions are needed in some cases!But restrictions are needed in some cases!
Idea: Idea: I’ll tell you if you sign this agreementI’ll tell you if you sign this agreement
Deterministically derive HASHES for parts of the Deterministically derive HASHES for parts of the RDF GraphRDF Graph
Use Semantic Digital Right Management Use Semantic Digital Right Management ontology to specify the policy and an OWL ontology to specify the policy and an OWL reasoner to verifyreasoner to verify
Give out the information if the other party agrees Give out the information if the other party agrees to put to put his/her digital signaturehis/her digital signature on the RDF on the RDF reppresentation of the reppresentation of the
POLICY +Information HASHPOLICY +Information HASH
Minimum Self-contained GraphMinimum Self-contained Graph (MSG) (MSG)
Involves (Def)Involves (Def) :An RDF statement :An RDF statement involvesinvolves a name if it has that name a name if it has that name as subject or object.as subject or object.
MSG (Def).MSG (Def). Given an RDF statement Given an RDF statement ss, the , the Minimum Self-contained Minimum Self-contained GraphGraph (MSG) containing that statement, written MSG( (MSG) containing that statement, written MSG(ss), is the set ), is the set of RDF statements comprised of the following:of RDF statements comprised of the following:
The statement in question;The statement in question; Recursively, for all the blank nodes Recursively, for all the blank nodes involvedinvolved by statements by statements
included in the description so far, the MSG of all the statements included in the description so far, the MSG of all the statements involving such blank nodes;involving such blank nodes;
MSG surrounding a URI: exampleMSG surrounding a URI: example
MSG(statement) (approx MSG(statement) (approx def). def). The “blank node closure” The “blank node closure” of the statement.of the statement.
MSG decomposition of RDF GraphsMSG 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: exampleMSG decomposition of a graph: example
Deterministic, content basedDeterministic, content based Identifiers for MSGs 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 licences.
RDF graph decomposition and identifiersRDF graph decomposition and identifiers
MSG ID = MD5(Canonical(MSG))MSG ID = MD5(Canonical(MSG))
= 45FA76B61FC0= 45FA76B61FC0
Graph MSGID list = Sort (MSG ID 1 , MSG ID 2, ..)Graph MSGID list = Sort (MSG ID 1 , MSG ID 2, ..)
Graph ID= Hash(MSGID)Graph ID= Hash(MSGID)
RDF/MSG decomposition applications (1)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.
mus:Band
mbz:artistid=15290
MD5:123123
mus:Song
mus:is_part_of
mus:file
rdf:type
rdf:type
mus:plays
rdf:statement
http://public../69..bd.pem
IdKtR...j4c=
rdf:type
dbin:Base64sigvalue
rdf:subject
rdf:predicate
rdf:object
dbin:X509Certificate
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 (2)RDF/MSG decomposition applications (2)Signing a Minimum Selfcontained Graph (MSG)Signing a Minimum Selfcontained Graph (MSG)
This paper! This paper! A procedure to serve information in RDF A procedure to serve information in RDF
subject to a previous agreement on the subject to a previous agreement on the use of that very informationuse of that very information
RDF/MSG decomposition applications (3)RDF/MSG decomposition applications (3)
The exchange procedureThe exchange procedureA 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 multimediaISO/IEC MPEG-21: about DRM on multimedia components: Rights Expression Language (REL) which components: Rights Expression Language (REL) which
uses terms explained in the Rights Data Dictionary uses terms explained in the Rights Data Dictionary
(RDD)(RDD) Lack of formal semantics! Lack of formal semantics!
the Copyright Ontology (OWL DL based) [1]the Copyright Ontology (OWL DL based) [1] As it deals with As it deals with Reproduction rightsReproduction rights and it is in OWL , fits and it is in OWL , fits
great with this our purpose!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. http://rhizomik.net/~roberto/thesis
An example licence instanceAn example licence instance
Licences are classesLicences are classes
To check an action: create an instance and use a DL classifier!To check an action: create an instance and use a DL classifier!
ConclusionsConclusions
A simple applications of RDF decompositionA simple applications of RDF decomposition
OWL based copyright ontology fits the task and stays in OWL based copyright ontology fits the task and stays in the domain of Semantic Web Toolsthe domain of Semantic Web Tools
To make it into a “legally binding” exchange mechanism, To make it into a “legally binding” exchange mechanism, specific laws might be neededspecific laws might be needed
Thanks for your attentionThanks for your attention
SEMEDIASemantic Web and Multimedia
Research Group on Human Computer Interaction and Databases