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