Naming Properties and Relations

Sep 13, 2009

This post is about how to name properties and relations in RDF schemas. Or rather, about how different ontology developers use different conventions and how this can sometimes be confusing.

Part of the work that I’ve been doing over the last few months at TSO has been for OPSI, who want to provide information about UK legislation for reuse through an API as well as eventually through a new end-user service. The Single Legislation Service API is now available, in beta, if you want to take a look.

One way in which we’re providing information about legislation is using RDF/XML. An example is the Criminal Justice Act 1993 Section 67, for which RDF is available at http://legislation.data.gov.uk/ukpga/1993/36/section/67/data.rdf. For now, we’ve made the decision to not attempt to create any of our own ontologies for the RDF, but to reuse ones that are already out there.

SPARQL & Visualisation Frustrations: Aggregation and Projection

Sep 12, 2009

Today, I’m going to moan about the lack of features in SPARQL that are necessary to do many kinds of data analysis and visualisation. Going from raw data, held in RDF, to data like

  • the average traffic flow along the M5
  • the total amount claimed by each MP
  • the number of corporate insolvency notices published each day

cannot be done with SPARQL on its own. These calculations involve aggregation, grouping and projection which are planned for SPARQL vNext, but not here yet (at least, not in any standard way or in every triplestore).

Here’s the pretty graph to illustrate today’s rant:

Corporate insolvency notices per day from the London Gazette since 1st May 2008, averaged over 20 days

On Resolvability

Aug 28, 2009

In my last post about RDFa and HTML I talked about how one of the gulfs that separates the HTML5 and Semantic Web communities is the attitude to the resolvability of property (and class) URIs.

I’m currently experimenting with introducing the ability to automatically locate information about properties and other resources that are referenced within triples to rdfQuery, so now is a good time, as far as I’m concerned, to look more closely at what the ability to resolve properties gives you and how to avoid problems if the property URI is (temporarily or permanently) unresolvable or resolvable to something new.

I’m going to attempt to answer:

  • How do or might applications use property and class URIs?
  • How can data and ontology publishers assist them in doing so?
  • What should frameworks (such as rdfQuery) do to help application developers?

More Crime

Aug 23, 2009

I wrote previously about a visualisation using Home Office data to navigate around categories of offences. The second interesting set of data from the Home Office that I found, tucked away in a small link on a page about Crime Reduction Toolkits was a spreadsheet of recorded crime statistics between 1898 and the present day. Each column is a different category of offence (I won’t say class because they don’t map onto the Classes from the spreadsheet of notifiable offences).

This time I wanted to try out the jQuery sparklines plug-in to illustrate how crime notifications have changed over time. The resulting page is available at http://www.jenitennison.com/visualisation/crime.html; here’s a screenshot for Bigamy:

Summary statistics for rate of Bigamy within the UK

HTML5/RDFa Arguments

Aug 21, 2009

When I came back from holiday, I caught up with the recent discussions around RDFa and HTML5. It’s exhausting reading so many posts repetitively reiterating the positions of people who all have the best of intentions but fundamentally different priorities. And such a shame that so much energy is spent on fruitless discussion when it could be spent at the very least improving specifications, if not testing, implementing, experimenting or otherwise in some very minor way changing the world.