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RDFBrowser

CSCI 8350, Spring 2002,UGA. RDFBrowser. Bernhard Schueler. A tool to analyse metadata. Overview. Intention Implementation Demo Where are the semantics? Unfinished feature: Synonyms, Homonyms, Similarity between RDF-Graphs What is unique about RDFBrowser. Intention.

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RDFBrowser

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  1. CSCI 8350, Spring 2002,UGA RDFBrowser Bernhard Schueler A tool to analyse metadata

  2. Overview • Intention • Implementation • Demo • Where are the semantics? • Unfinished feature: Synonyms, Homonyms, Similarity between RDF-Graphs • What is unique about RDFBrowser Bernhard Schueler - RDFBrowser

  3. Intention • Provide a tool to analyze RDF-based metadata. • This includes everything, which is or will be developed on top of RDF. • This tool should allow for: • Convenient browsing, • Comparisons between files, focusing on helping the user find semantic similarities/differences, • Synonyms, homonyms, graph similarity. Bernhard Schueler - RDFBrowser

  4. Implementation – Parsing • Parsing of RDF files: ARP, Another RDF Parser, by Jeremy Carrol, HP.Uses XERCES XML-parser. • I use this parser to extract the triples of the RDF data model. Bernhard Schueler - RDFBrowser

  5. Implementation – Knowledge base • RDFBrowser uses AMZI! Prolog to store and query the RDF triples. • AMZI! Prolog provides interfaces to Java, C, C++, Delphi and more. It runs under Windows and UNIX. • Prolog can easily be abused as database. First-argument indexing provides a certain efficiency. • I considered it to be convenient, especially for advanced inferences, such as finding synonyms (which unfortunately is unfinished) Bernhard Schueler - RDFBrowser

  6. Implementation – GUI • The graphical user interface is realized using Java (JDK 1.3.1), especially the “Swing” library. • All parts of the system run at least under Windows and UNIX. Bernhard Schueler - RDFBrowser

  7. Demo • Not in here … but on the screen (hopefully). Bernhard Schueler - RDFBrowser

  8. Where are the semantics? • RDFBrowser tries to overcome syntactic barriers to help the user retrieve the semantics. • The ability to simultaneously browse files should highlight semantic relationships. • A feature to find synonyms, homonyms, and similar structures in the underlying RDF graph would provide semantic analysis of • Different descriptions of the same domain, • Descriptions of different domains. Bernhard Schueler - RDFBrowser

  9. RDF graph Bernhard Schueler - RDFBrowser

  10. RDF graph – a matching Bernhard Schueler - RDFBrowser

  11. 2 Graphs Bernhard Schueler - RDFBrowser

  12. Search space – Example Bernhard Schueler - RDFBrowser

  13. Search space - Exponential • The (sub-)graph isomorphism problem is in NP. • The size of the search space is larger than n! . Precisely: n(1+ (n-1)(1+(n-2)(1+(n-3)…2(1+1).And that’s only exact matches! • 9 Nodes: more than 362880 possible matchings. Bernhard Schueler - RDFBrowser

  14. Pruning: Ullmann vs. A* Bernhard Schueler - RDFBrowser

  15. My Approach • Only querying of subgraphs of a small user defined length makes sense in a browser. • Inexact matches are more likely than an exact match of 42 Nodes. Bernhard Schueler - RDFBrowser

  16. My Approach – Pruning • Heuristics for pruning the search tree: • Same labels of nodes and edges (URIs), • Accuracy (percent of not matched nodes), • Consider only reachable nodes. Bernhard Schueler - RDFBrowser

  17. *Indexing techniques • There are advanced techniques for indexing graphs to speed up the average case, e.g. based on the number of adjacent nodes. • But imagine the tree of your direct ancestors (excluding uncles and aunts). Everyone has 2 parents… Bernhard Schueler - RDFBrowser

  18. What is unique about RDFBrowser • Regarding the semantic information contained in RDF files this browsers weakness is its strength: • It does not consider anything on top of RDF, e.g. RDFS, DAML, OIL. • Thus, it can work with any of them. Bernhard Schueler - RDFBrowser

  19. Literature • Dennis Shasha, Jason T. L. Wang, Rosalba Giugno. Algorithmics and Applications of Tree and Graph Searching. • Jeremy Carrol. Matching RDF Graphs. Draft, July 2001. • Koebler, Schoening, Toran. The Graph Isomorphism Problem: Its structural complexity.Birkhaeuser, Boston, 1993. Bernhard Schueler - RDFBrowser

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