ODBASE 0426.10.04

1
ODBASE 04 26.10.04

• A Necessary Condition for Semantic
  Interoperability in the Large
• Philippe Cudré-Mauroux and Karl Aberer
• School of Computer and Communication Sciences
• Swiss Federal Institute of Technology (EPFL)

2
Overview

• Peer DBMS
• Semantic graphs
• Semantic interoperability in large-scale networks
• Generatingfunctionologic model
• Results
• Use case scenarios
• Conclusions

3
Peer Data Management

• Local translations enabling global agreements

Photoshop Images peersCreator, Subject
Familiy X peerEvent
WinFS Images peersAuthor, Keyword
Creator
Author
Creator
Author
Creator
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On Translations
Q2ltGUIDgtp/GUIDlt/GUIDgt FOR p IN T12 WHERE
p/Creator LIKE "Robi"
Q1ltGUIDgtp/GUIDlt/GUIDgt FOR p IN
/Photoshop_Image WHERE p/Creator LIKE "Robi"
Photoshop (own schema)
WinFS (known schema)
ltPhotoshop_Imagegt ltGUIDgt178A8CD8865lt/GUIDgt
ltCreatorgtRobinsonlt/Creatorgt ltSubjectgt ltBaggt
ltItemgt Tunbridge Wells lt/Itemgt
ltItemgtRoyal Councillt/Itemgt lt/Baggt
lt/Subjectgt lt/Photoshop_Imagegt
ltWinFSImagegt ltGUIDgt178A8CD8866lt/GUIDgt ltAuthorgt
ltDisplayNamegt Henry Peach Robinson
ltDisplayNamegt ltRolegtPhotographerlt/Rolegt
ltAuthorgt ltKeywordgt Tunbridge
lt/Keywordgt lt/WinFSImagegt
T12 ltPhotoshop_Imagegt ltGUIDgtfs/GUIDlt/GUIDgt
ltCreatorgt fs/Author/DisplayName
lt/Creatorgtlt/Photoshop_ImagegtFOR fs IN
/WinFSImage

• ? Extending semantic integration techniques to
  decentralized settings!

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A Handful of Systems

• GridVine -- EPFL
• P-Grid access structure
• Principle of data independence
• Semantic Web compliant
• Semantic Gossiping
• Many other interesting systems
• Hyperion -- univ. Toronto
• Piazza -- univ. Washington
• Edutella -- univ. Hannover
• Mobile PDBMS -- univ. Trento
• Semantic Link Networks -- ICT China
• Etc.

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Schema-to-Schema Graph

• Inter-organization of the different schemas used
  by the peers
• Logical model
• Directed
• Weighted
• Redundant

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The Semantic Connectivity Graph

• Definition (Semantic Interoperability)
• Two peers are said to be semantically
  interoperable if they can forward queries to each
  other in the Schema-to-Schema graph, potentially
  through series of semantic translation links
• Idea
• As for physical network analyses, create a
  connectivity layer to account for semantic
  interoperability
• The semantic connectivity Graph S
• Unweighted, irreflexive and non-redundant version
  of the Schema-to-Schema graph

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Observations

• Theorem
• Peers in a set Ps are semantically
  interoperable iff Ss is strongly connected, with
  Ss ? s ?p ? Ps, p?s
• Observation 1
• A set of peers Ps cannot be semantically
  interoperable if
• Es lt Vs
• Observation 2
• A set of peers Ps is semantically
  interoperable if
• Es gt Vs (Vs-1) - (Vs-1)

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Semantic Interoperability in the Large

• Question
• How can we analyze semantic interoperability in
  large-scale Peer DBMS?
• Idea use percolation theory to detect the
  emergence of a strongly connected component in S
• Necessary condition for vertex-strong
  connectivity
• Necessary condition for semantic interoperability

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The Model

• Adaptation of a recent graph-theoretic framework
• Newman, Strogatz, Watts 2001
• Large-scale semantic graphs as random graphs with
  arbitrary degree distribution
• Exponentially distributed, small-world,
  scale-free graphs
• Specificities of our model
• Strong clustering (clustering coefficient cc)
• Bidirectionality (bidirectionality coefficient
  bc)
• Based on generatingfunctionality
• Percolation z2 z1 (second and first order
  neighbors)

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Main results (1)

• Necessary condition for semantic interoperability
  in the large ?j,k (jk-j(bccc)-k)pjk 0
• Apparition of a giant strongly-connected
  component

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Main results (2)

• Size of the out-component
• Propagation of a query through the semantic graph

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Main results (3)
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Use Case Scenarios

• Analyzing semantic interoperability in Peer DBMS
• Ways to determine statistical properties of the
  semantic graph
• Indexation using a common access structure (e.g.,
  DHT)
• Semantic crawlers
• Semantic random walkers
• Fostering semantic interoperability in the large
• Iterative approach
• Determine the semantic connectivity state
• Create semantic translations to reach
  super-critical phase

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Conclusions

• New focus on large-scale semantic systems
• From bilateral to multilateral analyses
• One possible avenue semantic connectivity graph
• Percolation theory
• Initial analysis
• Extensions to weighted models to predict quality
  of query dissemination
• Implementation in real systems on its way
• GridVine (EPFL)
• PicShark (EPFL -- Microsoft Research)

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ODBASE 04 26.10.04

• A Necessary Condition for Semantic
  Interoperability in the Large
• Philippe Cudré-Mauroux and Karl Aberer
• School of Computer and Communication Sciences
• Swiss Federal Institute of Technology (EPFL)