Steve Cassidy

RDF, the core data format for the Semantic Web, is increasingly being deployed both from automated sources and via human authoring either directly or through tools that generate RDF output. As individuals build up large amounts of RDF data and as groups begin to collaborate on authoring knowledge stores in RDF, the need for some kind of version management becomes apparent. While there are many version control systems available for program source code and even for XML data, the use of version control for RDF data is not a widely explored area. This paper examines an existing version control system for program source code, Darcs, which is grounded in a semi-formal theory of patches, and proposes an adaptation to directly manage versions of an RDF triple store.

Paper presented at ICSOFT 2007, Barcelona, Spain, July 2007. Download PDF

Gnowsis is a Semantic Web desktop System which means it aggregates various bits of personal data into an RDF store and provides a browser for the store. It is able to look at MP3-ID3 tags, email (in Outlook or Thunderbird), bookmarks in Firebird and at the file system. It will do full text indexing and provides a web server interface for browsing the store.

Which is weird because that’s just how Giggle is evolving at the moment. I’ve begun to build in an RDF store which in the first instance will just contain the individual weblog posts and their metadata (date, title, etc). The web pages and RSS feeds will then be generated from this store rather than from the tangle of variables in the current implementation. The page generation will still be template based but now the templates include references to the rdf store rather than simple variable references. One outcome of this is less of a need to precompute lots of variables for the templates (eg. the time of the post in minutes), instead letting the templates compute things from the store if they want to. Currently my new templates are coded as procedures which generate text (eg. HTML) and I’m using xmlgen to do the work internally.

Once I have an RDF store I can begin to put other bits of data in there. CANTCL already works on an RDF store populated from the package metadata. I could scan Tcl packages that I’ve written to generate something like my Tcl page. Drop some RDF annotated jpeg images into a directory and I could have a photoblog; scan my MP3 library, read my bookmarks, grok my calendar. The key to making this easy to use, which derives from the original blosxom idea, is to leave the data in it’s original format (or invent a simple text file format) and leverage the file system to build structure into the weblog.

I gave a talk last night at the MQ Technology Trends seminar series on the semantic web, my slides are here for those who wanted them.

In putting together the talk I think I understand my own view of SW a little better which is that the exciting thing is ubiquitous access to lots of useful data. The question of semantics keeps creeping in and while it’s important to be able to make inferences and use shared vocabularies, I’m not entirely convinced that there is any need for ‘real semantics’ to make interesting applications work. We need shared terminology and schema for sure, but there’s no more semantics there than when I use an XML schema to allow me to interoperate with others.

The big vision of autonomous agents crawling the web exchanging proofs and doing serious stuff for us will obviously face bigger problems than the vertical applications that can use agreed vocabularies. This is more like traditional AI applications and will obviously need some more knowledge representation which can be called semantics. However, I feel that all sorts of interesting things can be done without going this deep. Just look at what has become possible with RSS in the past few years; it’s the ubiquity of the data that makes things possible and without the ubiquitous data it’s hard to imagine the applications.

So, let’s continue the grass roots effort to populate the world with snippets of RDF metadata about anything that seems interesting. Get yourself a FOAF file, publish some RSS, add metadata to your photographs, publish your calendar. Now ponder what to do with all this glorious data!

The RDF query/manipulation proposals are coming out of the
woodwork on www-rdf-rules:

• XR does RDF extraction from
  XML
• Rx4RDF is ” a
  specification and reference implementation for querying, transforming
  and updating W3C’s RDF by specifying a deterministic mapping of the RDF
  model to the XML data model defined by XPath.”