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Q&A Session for “The RDFa initiative in Drupal 7, and how it will impact the Semantic Web”

By   /  May 6, 2010  /  No Comments

Q: How are the colleagues generated in the example? Manually nominated or picked up automatically by some social networking function?

Q: How are the colleagues generated in the example? Manually nominated or picked up automatically by some social networking function?

A: The example you are referring to is a typical website built with Drupal and Fields (formally known as CCK) where the users have created pages (of type person in the example) and they filled in all the information like name, picture and also they choose the list of colleagues from the list of other person described on the site. The colleagues haven’t been picked from a social network. This example only illustrating the generation of social network data with Drupal and its export in RDF. The other way around (importing) is something more tricky which is still at a prototype stage and should be available in the future for Drupal.

Q: How do we use http://opengraphprotocol.org/ of facebook as a source in Drupal?

A: Yes, you can use Open Graph protocol module for Drupal 7 I created a few days ago.

Q: Will you be persisting RDF data and if so by what mechanism?

A: Drupal core does not store RDF data as triples, but instead it generates the RDFa markup on the fly. Because the RDF mappings are defined ahead of time and not really RDFa specific, the data contained in a Drupal site can also be expressed in RDF triples and stored in an RDF store. In fact the RDF module which you can download for Drupal 7 already allows to get RDF/XML for each page of the site. There will be shortly a module to federate all this RDF data into a local store and expose it via a SPARQL endpoint.

Q: Please advise the whitepaper and example references you mentioned.

A: All the relevant links have been added to the webinar announcement.

Q: How big does the vocabulary in RDF & RDFa need to be before the general user population finds it useful?

A: I’m not sure to understand the question 100% but I’ll assume you’re talking about the amount of RDF triples on a given page. A few triples can make quite a difference for machines to understand what information they are looking at. To take a more practical example, you only need to have four elements in RDFa to have your page reusable by Facebook. Similarly, Yahoo! and Google only require a few triples to start making your data available as enriched search results. Typically less than 10 triples are enough to get a decent looking search result.

Q: So if we are not quite ready to try Drupal 7 in alpha, what do we need to install on Drupal 6 to play with RDFa?

A: I would recommend to wait until you can move to Drupal 7. RDF in support in Drupal 6 is quite difficult to set up, and there are feature like RDFa which are not really supported. Drupal 7 core has been design so that it’s possible to output RDFa and works better with RDF in general. Aside from that, Drupal 7 also has a lot of new features in term of usability, testing, APIs.

Q: Do you have any query interface built for querying RDF data?

A: That more of a generic RDF question which not only applies to Drupal but any application producing RDF data. See Freebase’s Parallax and Sparallax developed by DERI.

Q: Can you speak more about mapping and make some recommendations?

A: Drupal 7 core ships with some default RDF mappings for each built in content type like blog posts, articles, forums. You can change them or specify mappings for the new content types you might create on your site with the RDF module.

Q: Are there important RDFa standards to follow when setting up content types and fields so that they are represented consistently by search engines, etc?

A: Yahoo! and Google are still aligning their vocabularies. The best place to get the latest specifications is their webmaster documentations: Yahoo! SearchMonkey: Getting Started and Google Rich Snippets.

Q: When will a browser be able to follow RDF links?

A: Regular browsers like Firefox are already able to browse HTML pages which contain RDFa, except they are not yet able to understand what type of links they are traversing. For an RDF specific browser, see Tabulator.

Q: Also, what happens if/when there are changes made to RDF information types – how do they propagate and "push" the notification of changes to the sites displaying the data?

A: The syndication mechanism can be either a pulling of the information every so often like it is the case with regular RSS. A more sophisticated method can involve a pubsubhubbub setup where subscribers are notified every time there is a change. The work for integrating RDF and pubsubhubbub is currently on-going, see an example with sparqlPuSH

Q: Thanks for inviting me in this great seminar. I have an ontology which was implemented in OWL. May I import it into Drupal? What kind of modules I need to import using the specific ontology in Drupal, instead of generating RDF inside the Drupal?

A: The RDF mapping API in Drupal has been designed so it can deal with any ontology. The RDF external vocabulary importer in Drupal 6 was the first prototype of a module allowing to import any ontology into Drupal. It is currently being ported to Drupal 7 and you will be able to import your custom ontology to map your Drupal site data structure to your ontology.

Q: How ready is Drupal 7? I am an experienced developer but no Drupal experience

A: Drupal 7 is definitely usable: you can install it, create your site structure and create pages. It is not recommended to go production with it yet since there are still some known issue, but a good strategy is to start getting used to its new user interface and many other improvements; and start planning how you want to build your site with Drupal. Drupal 7 will be stable when all bugs are fixed, so if you are a developer you can help fix these remaining bugs. If you are not a developer there are many other ways you can contribute. New users are encouraged to download Drupal 7 and try it out.

Q: In your example you have the term ‘bear’ defined as a SKOS concept. I didn’t see any namespace in the markup. Would there be one or are all bears equal?

A: The namespaces in Drupal 7 are located at the very top of the HTML document, in the html tag. Drupal 7 includes the namespaces of Dublin Core, FOAF, SIOC, SKOS, etc. Developers can add their own custom namespaces via the RDF mapping API.

Q: Will Drupal 7 support discovery of vocabularies, and, help the administrator to choose the most appropriate vocabularity?

A: Yes, it will. The Produce and Consume Linked Data with Drupal! paper (PDF) goes well in details of the approach we are planning to use in Drupal 7.

Q: How easy will it be to tag a persons name in an article?

A: Drupal core does not deal with unstructured data within, say, the body of an article. People interested in this should look at modules like Calais or Zemanta which will detect these entities automatically for you.

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