Matt Butcher, author of Drupal 6 JavaScript and jQuery from Packt Publishing talks with Mike about the book and numerous topics regarding Drupal, JavaScript, and jQuery.

Matt is a senior programmer with Palantir and often writes about Drupal and other open source technologies on his blog, http://technosophos.com (listen to the podcast to learn what "technosophos" means). This is Matt's second Drupal book - he also wrote Learning Drupal 6 Module Developement in 2008.

The interview covers Drupal behaviors and its JavaScript templating system as well as some of the other ways Drupal developers can leverage JavaScript.

Packt has provided DrupalEasy with a couple of copies of the book to give away to listeners - listen to the interview to learn how you can get your hands on a free copy!

In the first three parts of this series, we've looked at what RDF will do for you as both a consumer and a provider of RDF data and we've had a quick primer on what exactly implementing RDF entails. Turning our attention back to Drupal, this article will take a look at the state of RDF in Drupal 6 and some of the available contribued modules. Tomorrow's article will take a look at what the next version of Drupal will offer in terms of RDF.

Drupal 6 does not have any RDF functionality in core. If you want to implement anything having to do with RDF in Drupal 6, you'll need to utilize contributed modules. Only a few of the RDF-related contribued modules for Drupal have even had official releases - the majority of them are still somewhere in the development process.

While reviewing the existing RDF modules for Drupal 6, I found that I could categorize them into two categories - "Provider Modules" and "Consumer Modules". Those in the former category are designed primarily to help you RDF-ize your site's content. Modules in the "Consumer" category are generally designed to help you consume, use, and display RDF data from various sources. In some cases, there is some overlap, so this categorization is more for convenience than anything else.

Provider Modules

RDF

The RDF module is the mothership of RDF modules for Drupal 6, providing a "uniform API and storage abstraction layer" (http://groups.drupal.org/node/8930) for RDF data. One of the cool things you can do with this module on its own is to RDF-ize your RSS feeds. Arto Bendiken, the author of the RDF module, provides step-by-step instructions for doing just this in his blog.

RDF External Vocabulary Mapper (EVOC)

This module provides a way to import external RDF ontologies into Drupal for use by other modules (RDF CCK, for one). For example, if you want to markup your event content using the RDF Calendar ontology, you can import it using this module, then it will be available to the RDF CCK module. Out of the box, this module provides support for the Dublin Core, Friend-of-a-Friend, and SIOC ontologies.

RDF CCK

This module allows you to provide your content in RDF format. It provides a "node/<nid>/rdf" page for desired content types; it does not provide RDFa output without a patch to CCK. This module is dependent on the following modules: CCK, RDF, RDF External Vocabulary Mapper, and SPARQL. If you're looking to output RDF or RDFa for your site's custom content types, this module is your best shot.

SIOC

The Semantically-Interconnected Online Communities (SIOC) ontology is often used to RDF-ize user forums, providing the ability to markup posts and comments by category, author, and other attributes. The SIOC module provides links to export RDF data for much of Drupal's default content, including nodes, users and comments. The module does not depend on the RDF (or any other) module and doesn't allow site admins to map RDF concepts to their site's content. On the upside, it is extremely easy to set up (there's virtually none) and provide RDF export data for a site's content using the SIOC, Dublin Core, and Friend-of-a-Friend ontologies. This module is kind of a lone wolf, not relying on any other RDF-related module.

Calias

This fantastic and mature module integrates with Thomson Reuters' amazing Calias web service to provide your content with more RDF data than most sites know what to do with. The RDF data is mainly provided in the form of Drupal vocabulary terms allowing you to leverage Views and other standard Drupal modules. Check out webchick's awesome writeup to learn more about how it works.

Calais Marmoset

Injects semantic data into your site's content when search robots access the site.

Topic Hubs

Works with the Calais module to provide site administrators and easy way to offer topic hubs for a site's tags. Integrates with Calais Geo (included in the Calais module) to display topic hub content on a map.

Open Dover

Similar to OpenCalias in that it is a web service that will provide semantic data for your content, but different in that its main goal is to "provide sentiment to your content" (http://www.opendover.nl/). For example, it makes an attempt to rate content as "positive" or "negative" based on advanced linguistic techniques.

Feed API RDF Processor

Works with the Feed API module to save feed data in RDF format.

Views Datasource

Provides a number of Views style plugins for displaying data in RDF (and other) formats.

Consumer Modules

SPARQL

Dries Buytaert demoed an early version of the SPARQL module back in 2008 at DrupalCon Boston. More than any other RDF module, it really shows how RDF has the potential to change the way the web works. The SPARQL module allows you to query local and remote RDF data using a language similar to SQL. It takes some prerequisite RDF knowledge to get results from this module, unfortunately, there's not a whole lot of Drupal-sepcific information out there for beginners. Wikipedia's SPARQL page is a good place to get started.

Exhibit

This module utilizes the Exhibit Publishing Framework to give you the ability to display data with advanced filter and search capabilities using RDF. A nice example of the framework's functionality can be found in this "Recent United States Senate Bills" page. The Potluck module enhances Exhibit-powered pages by providing a tool to re-mix the data. If anyone knows of a public-facing Drupal site utilizing the Exhibit module, please post it in the comments below.

Obviously, there's a lot going on with RDF in the Drupal community. The Semantic Web group is a great place to find out the latest going-ons. If you know of any additional examples in use of any of the modules listed above, please list them in the comments!

Thanks to  Benjamin Melançon of the Agaric Design Collective for his assistance with this article. Benjamin is an active member of the Drupal community and attended the "RDF in Core" sprint in May, 2009.

This is part 4 in a 5 part series about RDF and Drupal.

1. RDF in Drupal: What is it and Why Should We Care?
2. RDF in Drupal: Benefits to Casual Web Surfers
3. RDF in Drupal: Super-Simple Primer
4. RDF in Drupal: What can I do now? Drupal 6 and the Semantic Web
5. RDF in Drupal: The Future - RDF in Drupal 7

Even if you're not ready to implement RDF into your Drupal site, there's still a number of reasons why you should be excited about the Semantic Web. The fact that data will be linked from web site to web site (regardless of the underlying technology running the site) will lead to powerful Semantic Web applications - most of which haven't even been imagined yet.

First and foremost, search will be revolutionized. Imagine being able to search for a specific person - not just the person's name. This is a subtle but important distinction. Currently, when you type "Dave Matthews" into your favorite search engine, the results you see are based on the words "Dave" and "Matthews". You'll see results about Dave Matthews, about people with the name "Dave" and/or "Matthews", about the orgin of the words "Dave" and "Matthews", etc... The search engine doesn't know that you're looking for a specific person with the name "Dave Matthews". With the Semantic Web, you'll be able to specify, "find me the person with the name 'Dave Matthews'". You'll even be able to perform "deeper" searches by specifying things like "find me all events having to do with Drupal taking place between now and July".

Other than search, the Semantic Web will also provide you with the ability to do stuff with this data. For example, let's say you perform the Drupal events search from the previous paragraph and you're looking at the results. Because the data returned will have meta-data attached to it, future software tools will allow you to click on a returned event, and see if you're available on that date and time. If so, another click will seamlessly add it to your calendar. If you're familiar with Mac OS X, it's like data detectors on steriods. Really good steriods.

Another future use for the Semantic Web that will no doubt be huge is that it has the potential to turn the entire web into a social network - owned and operated by all of us. The Friend of a Friend project (FOAF) is an RDF vocabulary that describes people and relationships between them. By implementing FOAF on existing web site, you can indicate relationships between your users. These relationships can then be combined with other relationships on other sites to produce a social network.

While most of the whiz-bang capabilities described here have not yet come to pass just yet - they all have one thing in common - they require that web sites start implementing RDF now. Lots of large sites have done so, and more are being added every day. One of the more well-known sites that has begun implementing RDF is Digg.com. They are using the Dublin Core vocabulary for content attribution (additional details).

The Data Portability Project is an industry initiative "To help people to use and protect the data they create on networked services, and to advocate for compliance with the values of DataPortability." If you have any doubt about the future of the Semantic Web, some of their members include Facebook, Google, Microsoft, and LinkedIn.

This is part 2 in a 5 part series about RDF and Drupal.

1. RDF in Drupal: What is it and Why Should We Care?
2. RDF in Drupal: Benefits to Casual Web Surfers
3. RDF in Drupal: Super-Simple Primer
4. RDF in Drupal: What can I do now? Drupal 6 and the Semantic Web
5. RDF in Drupal: The Future - RDF in Drupal 7

RDF. Semantic Web. Giant Global Graph. Food for Robots. By now you've probably heard all of these phrases, but relatively few of us have actually done anything with them. For example, I try to follow all the RDF modules on Drupal.org, read all the blog posts regarding Drupal and RDF but I've yet to implement anything having to do with RDF on any of the sites I develop or maintain. Why is this? Am I behind the curve?

The answer is two-fold. First, I have yet to have any clients specifically ask for RDF functionality in their web sites. Secondly, I hadn't been convinced that recommending that my clients spend the time and money to implement an RDF solution is a sensible move for them. The reason I decided to research and write this series of articles is to figure out if and why I should recommend implementing RDF functionality to my clients.

Prior to performing the research for this series, my knowledge of RDF was limited to water-cooler-conversation type knowledge. Big on bulletpoints, small on details. I was aware that RDF will, in the future, be used by search engines to provide better search results. I was also aware that by "tagging" web site content with RDF would enable a "richer" experience. The one example I would relay to people was a vCard-powered business card embedded on a web page using microformats that allowed the user's computer to do something with the contact information. Amusingly, it turned out that my one RDF example didn't even involve RDF, and that the vCard format was actually called hCard when used as a microformat. I had a lot to learn.

Definition

Just so we're all on the same page, RDF stands for "Resource Description Framework". The current HTML-based structure of the web it great for us humans, but it is difficult for computers to make sense of all the data. RDF is a framework to describe information on the web that makes it easy for software programs to process.

Industry Support and Momentum

As Drupal project lead Dries Buytaert pointed out in a blog post, Google has announced Rich Snippets - its first (of many, I'm sure) way of utilizing RDF and other semantic markup formats in its search results. Cutting to the chase, implementing RDF now can lead to better search rankings for your site.

With Google's big announcement and Yahoo already on-board (Microsoft isn't sitting still either), now is a good time to get down to brass tacks and start talking about implementing RDF your Drupal sites.

Benefits to Site Administrators and Owners

As I mentioned, implementing RDF today has the potential of immediately leading to better search rankings - contingent on how quickly Google and other search providers fully roll out their RDF capabilities. If you've been paying any attention at all to RDF and the Semantic Web, then you'll know that better search rankings are only the tip of the iceberg.

By adding RDF data to your site you are, in effect, giving absolute meaning and context to your content. This means that you can allow present and future Semantic Web applications to absolutely know that the text "Ice Cube" on your site refers to the rap artist and not an actual ice cube. Then, when other sites markup their Ice Cube text in the same way your site does, your data is in effect, linked using RDF. Applications can then utliize these links to create mashups and add additional value to your data. Extrapolate this out past just people's names but also events, relationships, and topics and you'll realize how powerful RDF can be. This is the Giant Global Graph that Tim Berners-Lee first envisioned (yeah, his blog runs on Drupal).

While there will definitely be people and organizations that argue that they don't want their data "linked" with anything for proprietary reasons, most RDF proponents argue that linking your data with other people's data makes it more valuble. It stands to reason that RDF will follow Metcalfe's Law - the value of the RDF "network" is proportional to the square of the number of connected datapoints. The more data that is connected using RDF, the more valuble your data becomes. A great example of Metcalfe's Law is the fax machine (thanks Ryan). If you're the only one with a fax machine, it kind of sucks. Once all your friends get fax machines, it's kind of awesome. Imagine the same senario but with RDF.

Another immediate benefit, should you choose to pursue it, is the ability to use a technology like SPARQL to start linking your site's data to other RDF-ized data and presenting it back to your users in a format they can use (check out the Drupal SPARQL module). This is precisely what Dries showed during his keynote at DrupalCon Boston in 2008.

Implementing RDF now will put you ahead of the Semantic Web curve. Tom Scott summed things up nicely on his blog in his Semantic web - why bother? post:

As a publisher of linked data not only are you enabling others to build cool things with your data – helping you right now – you are also helping to insulate yourself against atrophy. If your data is as open and accessible as possible – then it is relatively straight forward for your future colleagues, working on a as yet unimagined product, to use the data you are publishing right now.

This article is the first in a five-part series about RDF on DrupalEasy.com. Over the next 4 days, I'll be delving deeper into RDF and Drupal:

1. RDF in Drupal: What is it and Why Should We Care?
2. RDF in Drupal: Benefits to Casual Web Surfers
3. RDF in Drupal: Super-Simple Primer
4. RDF in Drupal: What can I do now? Drupal 6 and the Semantic Web
5. RDF in Drupal: The Future - RDF in Drupal 7