Graph Versioning System

Reto Bachmann-Gmür, Chris Dollin

Hewlett-Packard Development Company, L.P.

RDF and change

• Ontologies can model the time-dimension
• Ontologies rarely take into account that the described world is changing
• For many use-cases change aware ontologies aren't needed and would make things more complicated
• It's impossible to foresee everything that could change

Approaches

• Triple-oriented approach
• Decomposition-oriented approach

Architecture

• Deterministic lossless decomposition
  • RDF-Molecules
  • Functionally Grounded Nodes
• Metamodel: what, when, where

API: The Store

• class com.hp.hpl.jena.gvs.Store
  • GraphOverTime getGraphOverTime(Set<Source> sources);
  • void assertGraph(Source source, Graph graph, Date date);
  • void revokeGraph(Source source, Graph graph, Date date);
  • void updateGraph(Source source, Graph graph, Date date);
  • Set<Source> getSources();

API: Graph Over Time

• class com.hp.hpl.jena.gvs.GraphOverTime
  • Graph getGraph(Date moment);
  • void assertGraph(Source source, Graph graph, Date date);
  • Iterator<Date> previousChanges(Date d);
  • Iterator<Date> followingChanges(Date d);

Yet another Graph

• interface Graph extends Collection<Triple>
• Inmutable
• Identity criterion
• Java 5

Application

• Command line tools
• Services: HTTP, Aggregator

HTTP Access

• RESTful interface
• AJAX Application

Where to go?

• Access Control
• Documentation
• Performance
• Jena Model-Wrapper
• Oh, yeah? - feature
• Querying
• Resource oriented browsing
• Remote Synchronization
• Extracting Diffs

Perfomance improvement

• Strong hash on all molecules which can be predictably serialized and on all fg-nodes

Relations between components

Thanks

• ...