RDFa

Back in June, Google, Bing and Yahoo! announced a joint effort to build a schema for describing content the web. The first schema.org workshop took place last week in Mountain View, CA. I had the chance to participate in the event, and meet the folks behind schema.org as well as other members of the web community such as Tantek Celik (Microformats), Ian Hickson (HTML5), Ben Adida & Ivan Herman (RDFa), Dan Brickley (FOAF) and many others. RV Guha from Google announced several interesting schema.org partnerships:

• The office of CTO at the White House is planning to annotate educational content, lectures, reporting and open job listings using schema.org.
• The Learning Resource Metadata Initiative (LRMI), an industry-specific framework to make quality educational resources easily searchable for teachers and learners, is planning to build an extension for schema.org.
• schema.org has added support for rNews, a standard for embedding news publishing metadata into web pages developed by the International Press Telecommunications Council (IPTC)

Lots going on around schema.org! You can read Eric Franzon's report for more details: Schema.org Workshop – A Path Forward.

In Drupal 7 we often use multiple types to describe pieces of content, for example a node is a sioc:Post and a foaf:Document, a comment a sioc:Post and a sioct:Comment. This is useful when you want to be generic and specific at the same time, or when a consumer only recognizes one vocabulary and not the other. For example imagine that you want to combine Facebook's Open Graph protocol and schema.org vocabularies onto the same page elements so that your blog posts are recognized by Facebook, Google and Bing. Another use case is a news website using rNews, a proposed standard developed by the IPTC for annotating news-specific metadata. There is great incentive for such news website to also be indexed by the major search engines, which will only recognize the schema.org vocabularies.

Update: alex b posted another interesting use case on the schemaorg-discussion mailing list:

I can imagine that some businesses may fit into more than one Schema
tag. Will there be a problem with applying more than one? For
example I might want to apply the following tags to a car dealer:
AutoDealer,
AutoRepair, AutoPartsStore if they perform all of these functions of
course. Is this going to fly or is this something we're not
supposed to do?

From the use cases above, it is clear that the ability to combine vocabularies is essential for allowing a decentralized extensibility on the Web.

Today it's about time to make my M.Sc. thesis available online. The review process took a long while, but I finally graduated from DERI, National University of Ireland, Galway last October. That's more than a year after I submitted my thesis and actually left Galway to move to Boston.

A couple of days after Dries Buytaert gave his keynote at DrupalCon San Francisco and reaffirmed his support for the Semantic Web in Drupal, Facebook co-founder Mark Zuckerberg announced at the f8 developer conference the brand new Open Graph protocol, a technology to turn webpages into social objects and capture them in a social graph. The announcement was backed up by a lot of PR and according to Facebook, 50,000 websites have already implemented OGP including IMDb, NHL, Posterous, Pandora, Rotten Tomatoes, Yelp and more. There is plenty to read about the marketing around this announcement, but I'm going to keep this post at a technical level only.

The first alpha release of Drupal 7 will be created next Friday Jan 15th. We've already incorporated most of the feedback we received from the semweb community so far, but I wanted to give the community a last chance to review the RDFa markup and the default RDF mappings we use before it's too late. I should emphasize that all the markup and default RDF mappings that we ship in core will be pretty much set in stone after the stable release of Drupal 7, hence this call for feedback. Site administrators who care about semantics will be able to alter these mappings by installing extra modules, but many people (read several 10K sites) will just install Drupal 7 and not care about the semantics it generates. Therefore we want to make sure the RDFa generated by Drupal out of the box is somewhat correct and does not make folks from the semantic/pedantic web community angry :) - we've tried to keep the semantics as generic as possible for that reason.

RDF mappings

I've created a diagram representing the default semantics of the core data structure which has been committed and I would appreciate feedback on the RDF terms we've used.

RDFa markup

To make the RDFa markup review process easier, I've updated the usual testing site at http://drupalrdf.openspring.net/. It features a blog post with some comments which represents a typical Drupal 7 page annotated with RDFa. Some other pages have been randomly generated to be able to test the tracker which acts as a very simple sitemap in RDFa.

I had the pleasure to give a presentation of the paper "Produce and Consume Linked Data with Drupal!" at ISWC2009 last, and I was very honored we won the Best Semantic Web in Use Paper award! The 30 minutes of presentation + Q/A passed very quickly and I didn't have much time to expand on the status of RDF in Drupal 7 vs. Drupal 6 after describing the inner workings of the modules we developed. I'm sure this will also interest some people outside the attendees. First of all, the current stable version of Drupal is Drupal 6 (the latest version at the time of this writing being Drupal 6.14). This is the version on which we started to implement the contributed modules presented at ISWC2009, namely RDF CCK, RDF external vocabulary importer (Evoc), SPARQL Endpoint and RDF SPARQL Proxy. Contributed modules means they do not get included in the core Drupal package, but people can download them from drupal.org for free and drop them on their server so Drupal core can be extended. These 4 modules work pretty well on Drupal 6, you can get RDF export in RDF/XML, N-Triples, turtle, json. However generating RDFa is not very easy as it requires to patch the CCK on which we rely to generate the content pages and store the various field data. We made sure this would not be a problem in the next version of Drupal (Drupal 7) which is still under development, and due to be released sometime next year.

Produce and Consume Linked Data with Drupal! is the title of the paper I will be presenting next week at the 8th International Semantic Web Conference (ISWC 2009) in Washington, DC. I wrote it at the end of M.Sc. at DERI, in partnership with the Harvard Medical School and the Massachusetts General Hospital which is where I am now working.

It presents the approach for using Drupal (or any other CMS) as a Linked Data producer and consumer platform. Some part of this approach were used in the RDF API that Dries committed a few days ago to Drupal core. I have attached the full paper, and here is the abstract:

Currently a large number of Web sites are driven by Content Management Systems (CMS) which manage textual and multimedia content but also - inherently - carry valuable information about a site's structure and content model. Exposing this structured information to the Web of Data has so far required considerable expertise in RDF and OWL modelling and additional programming effort. In this paper we tackle one of the most popular CMS: Drupal. We enable site administrators to export their site content model and data to the Web of Data without requiring extensive knowledge on Semantic Web technologies. Our modules create RDFa annotations and - optionally - a SPARQL endpoint for any Drupal site out of the box. Likewise, we add the means to map the site data to existing ontologies on the Web with a search interface to find commonly used ontology terms. We also allow a Drupal site administrator to include existing RDF data from remote SPARQL endpoints on the Web in the site. When brought together, these features allow networked RDF Drupal sites that reuse and enrich Linked Data. We finally discuss the adoption of our modules and report on a use case in the biomedical field and the current status of its deployment.

We're half way through the sprint and we just heard that Google has announced support for RDFa. What a coincidence, surely another sign proving Drupal's heading in the right direction! Now is time for some update on the sprint.

During day 1, we decided to split the group into two in order to enable some parallel developement and to make use of the 2 main skills we had at hand: RDF semantics and Drupal coding.

This is the video which was presented during DrupalCon DC 2009 at the Practical Semantic Web and Why You Should Care session.

Exciting times for the Semantic Web in Drupal...

Harvard IIC and SCF

Today is my first day at Harvard's Initiative in Innovative Computing where I'll work on the Drupal based Science Collaboration Framework (SCF) project with Tim Clark, Sudeshna Das and Benjamin Melançon. I had the chance to meet Tim last year when he visited DERI and presented the SCF project. We'll work on aligning the efforts which were put into SCF with the efforts of the Drupal community in terms of RDF. We will see what requirements are emerging from a project such as SCF and contribute them back to the Drupal community.