1. ODBASE 0426.10.04 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 Author Creator WinFS Images peers Author, Keyword… Photoshop Images peers Creator, Subject … Familiy X peer Event Creator  Event Creator  Author Author  Creator Local translations enabling global agreements 0.1 0.9 0.8

4. On Translations Q1= $p/GUID FOR $p IN /Photoshop_Image WHERE $p/Creator LIKE "%Robi%" 178A8CD8865 Robinson Tunbridge Wells Royal Council … Photoshop (own schema) 178A8CD8866 Henry Peach Robinson Photographer Tunbridge … WinFS (known schema ) T12 = $fs/GUID $fs/Author/DisplayName FOR $fs IN /WinFSImage Q2= $p/GUID FOR $p IN T12 WHERE $p/Creator LIKE "%Robi%"  Extending semantic integration techniques to decentralized settings!

5. 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.

6. Schema-to-Schema Graph Inter-organization of the different schemas used by the peers - Logical model - Directed - Weighted - Redundant

7. 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

8. Observations Theorem Peers in a set P s are semantically interoperable iff S s is strongly connected, with S s  {s |  p  P s, p  s} Observation 1 A set of peers P s cannot be semantically interoperable if |E s | < |V s | Observation 2 A set of peers P s is semantically interoperable if |E s | > |V s | (|V s |-1) - (|V s |-1)

9. 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

10. 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: z 2 ≥ z 1 (second and first order neighbors)

11. Main results (1) Necessary condition for semantic interoperability in the large:  j,k (jk-j(bc+cc)-k)p jk ≥ 0 –Apparition of a giant strongly-connected component

12. Main results (2) Size of the out-component –Propagation of a query through the semantic graph –

13. Main results (3)

14. 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

15. 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)

16. ODBASE 0426.10.04 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)