The Semantic Puzzle

Pascal Hitzler

A (very personal) bit of ISWC08 trendspotting

As ISWC08 is drawing to a close, it dawns to me that something which Frank van Harmelen has been forecasting for years is now happening, seemingless without conscious effort. He calls it Approximate Reasoning – have a look at his ESWC06 keynote. The basic idea behind it is to do reasoning over ontologies with a different focus, namely by giving up some reasoning correctness in order to gain better scalability.

And indeed, at ISWC08 I have seen a number of things which fit exactly into this corner (while at the same time the authors/programmers might not even be aware of it).

  • As part of the Billion Triple Challenge, Axel Polleres presented the SAOR system, which does approximate OWL reasoning by means of forward chaining rules. Now you can’t do OWL reasoning (in a sound and complete way) with forward chaining rules (and Axel knows this), so in the end you’re losing some consequences. But at the same time you do get some consequences when having to deal with large amounts of data.
  • Eyal Oren, also at the Billion Triple Challenge, presented the MARVIN system which performs approximate RDF reasoning by means of massive parallelisation. MARVIN comes out of the EU project LarKC, which is actually pursuing approximate reasoning on a large scale (pun intended). Edit: This one actually won the 3rd prize at the challenge.
  • Among the results presented at ISWC08, I found those by Claudia D’Amato on Statistical Learning for Inductive Query Answering on OWL Ontologies really amazing. She and her collaborators managed to do OWL instance retrieval without any deduction algorithm. Instead they used Support Vector Machines and learned which (named) OWL classes individuals belong to. The learning was done from a small sample set (generated by a reasoner), but the network was able to generalise from the data to achieve about 90% of coverage. In my opinion, this is something conceptually new and it is really remarkable that it works.
  • In a regular paper Eyal Oren also reported on using Evolutionary Algorithms for RDF query answering.

The above is only a selection of approximate reasoning related things at ISWC08. There was also the Workshop on Nature inspired Reasoning for the Semantic Web where related ideas were discussed. At the colocated Web Reasoning and Rule Systems conference, RR2008, there will be two papers on approximate reasoning (incidentially, with me as coauthor).

I foresee the importance of such approaches rising substiantially in the future (and I think it’s a safe guess since Frank also seems to think so). The Billion Triple Challenge series could become one of the driving forums for this. There are exciting times ahead!

Author: Pascal Hitzler, AIFB, University of Karlsruhe (TH), Germany