Thinking Clearly .

At Semantic Technology 2009 we formally announced PelletDb, our new product that integrates Pellet with Oracle’s Semantic Database system, including the Oracle RDF query engine and OWL reasoner. We’re excited about PelletDb since it makes Pellet available to Oracle users, including its sound and correct OWL 2 reasoning, unique reasoning services like SPARQL-DL and explanations, etc. But we’re also excited because it makes Oracle’s enterprise-class information management facilities available to Pellet users and apps.

Today we’re releasing an extensive PelletDb whitepaper (PDF) that explains in detail what PelletDb is, how it works, who should use it, etc. It includes customer benefits, sample code, and a basic roadmap for future development. If you’re curious about how we’re fusing Pellet and Oracle, check out the whitepaper.

The PelletDb limited beta is on-track to begin 15 July, so please get in touch if you want to participate.

Two weeks ago at Semantic Technology 2009 conference Evren and Mike presented a 4 hour tutorial about building OWL-based applications with Pellet 2. About 50 people attended, which was a surprising turnout given that it was at the rump end of the conference, a notoriously difficult time slot.

After some polishing based on feedback, we’re making the tutorial materials, including sample code, slides, and a bundled download of Pellet, available for use in learning (or teaching others) how to use Pellet, both interactively and programmatically.

Enjoy!

In anticipation of our Pellet tutorial at the Semantic Technology Conference next week, we’ve made a new release candidate for Pellet 2.0 available for download. Pellet 2.0 RC7 improves on previous releases by resolving several exception-causing bugs reported by users, improving the lint tool’s support for the OWL 2 specification, and enhancing the inference explanation command line tool. The release also includes an update to Jena 2.6. This change is mostly backwards compatible for users with older Jena versions, but users depending on SPARQL query will need Jena 2.6. All of these changes are described in a Pellet Trac report.

Pellet Reasoner Plug-in for Protégé 4 has also been updated. Existing users should be prompted for an automatic upgrade to plug-in version 0.9.3.

Please continue to send your bug reports to the Pellet users mailing list. As always, you can influence the future of Pellet by contacting us to start a support relationship.

We’re excited about SemTech 2009 in June for many reasons, including the 5 talks we’re giving:

1. Introducing OWL 2: A Panel and Community Discussion, featuring Mike Smith, who’s one of the OWL 2 Test Suite editors; Ian Horrocks (Oxford), Ivan Herman (W3C), Deb McGuinness (RPI), and Zhe Wu (Oracle).
2. Faceted Browsing Tools where Mike Grove will talk about jSpace, our faceted visual query browser for SPARQL.
3. Government Sidebar, where Evren Sirin and Mike Smith will talk about HTN-DL Planner and the work we’ve done with Kevin Newman and John T. Carson from Lockheed Martin on planning UAVs;
4. Managing OWL: Using Oracle and Pellet for Massively Scalable, Highly Expressive OWL Infrastructure where Xavier Lopez from Oracle and I will talk about the work we’ve done to combine Oracle’s scalable reasoning with Pellet’s expressive reasoning in PelletDb, a new offering from us later this year;
5. A Programmer’s Introduction to Pellet: How to Build Ontology-based Semantic Applications where Evren and Mike Smith will give a 3-hour tutorial on how to build real OWL applications based on Pellet (where “real” means “uses inference in anger” and “is semantics-respecting”).

At SemTech 2008 our talks focused on R&D work we’d been doing around OWL reasoning with Pellet, probabilistic reasoning with Pronto, etc. This year our talks are much more tightly focused on industrial applications of Pellet, automatic planning, and SPARQL tools, as well as our standards work at W3C.

See you in San Jose!

In an earlier post, Evren talks about our implementation of integrity constraints using SPARQL queries where we are turning the constraints into queries which we then post to the KB in order to determine if there was a violation of the constraint.

I’ve been working on an internal project lately, and while we were having a code review the other day, we decided that adding some validation via integrity constraints would be useful.  The catch was that I’m using Sesame, in particular, Sesame 1.2.7 since that offers the best query performance of their whole line of software (at least it did the last time I checked).  And since I am using the older Sesame API, I’m without SPARQL support.  This makes it difficult for me to repurpose our IC prototype since it’s based on Jena and SPARQL.

So I worked on an implementation of our IC interface that was based on the Sesame API and used SeRQL.  This turned out to be vastly easier than I expected.  One of the workaround’s we used for the SPARQL-based implementation was the OPTIONAL/FILTER/!BOUND pattern because SPARQL does not provide a NOT keyword for encoding Negation as Failure.  As it turned out, I didn’t need to implement a workaround like this using SERQL. I was able to get by using the NOT & IN keywords with a subquery to get the same behavior. The resulting queries are very clear.  So with some code to translate the constraints into SERQL queries, and a Sail implementation backed by a Pellet KnowledgeBase, we get the same IC joy in Sesame projects as we do with Jena and SPARQL.

This is good fodder for the new SPARQL working group that we’re participating in (nominally, so far); I believe subqueries and negation are both being considered.  They would make great additions to the revised SPARQL.