ODBASE 0426.10.04

A Necessary Condition for Semantic Interoperability in

the Large

Philippe Cudré-Mauroux and Karl AbererSchool of Computer and Communication Sciences

Swiss Federal Institute of Technology (EPFL)

Overview

• Peer DBMS

• Semantic graphs

• Semantic interoperability in large-scale networks

• Generatingfunctionologic model

• Results

• Use case scenarios

• Conclusions

Peer Data Management

Author

Author

Creator

Creator

Creator

WinFS Images peersAuthor, Keyword…

Photoshop Images peersCreator, Subject …

Familiy X peerEvent

Creator Event

Creator Author

Author Creator

• Local translations enabling global agreements

0.1

0.9

0.8

On Translations

Q1=<GUID>$p/GUID</GUID> FOR $p IN /Photoshop_Image WHERE $p/Creator LIKE "%Robi%"

<Photoshop_Image> <GUID>178A8CD8865</GUID> <Creator>Robinson</Creator> <Subject> <Bag> <Item> Tunbridge Wells </Item> <Item>Royal Council</Item> </Bag> </Subject> …</Photoshop_Image>

Photoshop(own schema)

<WinFSImage> <GUID>178A8CD8866</GUID> <Author> <DisplayName> Henry Peach Robinson <DisplayName> <Role>Photographer</Role> <Author> <Keyword> Tunbridge </Keyword>…</WinFSImage>

WinFS (known schema)

T12 =<Photoshop_Image> <GUID>$fs/GUID</GUID> <Creator> $fs/Author/DisplayName </Creator></Photoshop_Image>FOR $fs IN /WinFSImage

Q2=<GUID>$p/GUID</GUID> FOR $p IN T12 WHERE $p/Creator LIKE "%Robi%"

Extending semantic integration techniques to decentralized settings!

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.

Schema-to-Schema Graph

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

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

Observations

• Theorem Peers in a set Ps are semantically interoperable iff Ss is

strongly connected, with Ss {s | p Ps, ps}

• Observation 1 A set of peers Ps cannot be semantically interoperable if

|Es| < |Vs|

• Observation 2 A set of peers Ps is semantically interoperable if

|Es| > |Vs| (|Vs|-1) - (|Vs|-1)

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

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)

Main results (1)

• Necessary condition for semantic interoperability in the large: j,k (jk-j(bc+cc)-k)pjk ≥ 0– Apparition of a giant strongly-connected component

Main results (2)

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

Main results (3)

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

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)

ODBASE 0426.10.04

A Necessary Condition for Semantic Interoperability in

the Large

Philippe Cudré-Mauroux and Karl AbererSchool of Computer and Communication Sciences

Swiss Federal Institute of Technology (EPFL)