Semantic Web Publishing with RDFa
Tools are emerging from the RDF world at an accelerating pace this year, and you may find what you need without writing a line of code. Not all of them produce RDFa, however. Some, such as Semantic MediaWiki, produce the HTML and RDF side by side, from an internal triple store. It's a fair chance you've already used RSS (which originally stood for RDF Site Summary when it was created at Netscape back in 1999). If you use version 1.0, take a look at the RSS source—it's valid RDF/XML.
Another group to keep an eye on is the Simile Project at MIT. It has an interesting range of tools with the broad purpose of managing and reusing bits of digital data. Not all are RDF-related, but the RDFizer promises to convert a variety of structured formats to RDF for you: mbox, Debian software packages, Subversion and many more.
The most advanced tools probably are not yet in the open-source arena. Metatomix, Inc., has done some heavy lifting in the semantic application field, with major implementations in engineering, finance and integrated justice. I talked to CTO Howard Greenblatt, and he explained the company's technology stack. The key components are first, a set of development tools for creating the ontology, and second, a messaging platform that gathers data from traditional data sources and integrates it into a triple store, along with some business rules logic. For the first component, they have their own plugin for the Eclipse development environment, and for the second, they use Jena from HP Labs plus a bunch of proprietary code. Then, the whole thing can be queried in SPARQL, the query language of the Semantic Web.
That's more than most Web developers are likely to bite off. However, it brings us back to a point from our example above: choosing, or creating, an appropriate vocabulary. To say anything on the Semantic Web, you have to have a namespace in which to speak precisely. Writing your own vocabulary is not too hard (and Semantic MediaWiki helps you do it automatically), but you may want to choose a standard one, at least if you are interested in search engine discovery.
Yahoo announced in March 2008 that it would start supporting Semantic Web standards, including microformats, RDFa and eRDF. And, it announced specific vocabulary components that would be supported: Dublin Core, Creative Commons, FOAF, GeoRSS and MediaRSS. Using these vocabularies will make your data more portable and easier for search engines to index intelligently.
If you want to see what vocabularies others are using, the GetN3 bookmarklet is helpful. A visit to digg.com, run through the GetN3 bookmarklet, shows that Digg is now embedding RDFa using the Dublin Core and Creative Commons vocabularies (prefixes added):
<http://digg.com/> cc:attributionName "Digg users"; cc:license cclicense:publicdomain/; ... <http://digg.com/space/Jules_Verne_in_Orbit> dc:source <http://apod.nasa.gov...>; dc:title "Jules Verne in Orbit"; dc:abstract "The bright edge of planet Earth.."; dc:creator <http://digg.com/users/ezentmyer>; dc:date "2008-04-05 05:07:38";
I think the Semantic Web is finally taking off this year. Semantic applications range from personal desktop productivity (MIT's Piggybank) to new Web search engines (Yahoo) to huge enterprise applications and even military information-sharing. As the social networks grow heavy with data, sharing and structuring that data becomes more important. Eric Miller, an MIT professor who led the Semantic Web initiative for the W3C, sees “a new market space for data aggregation, data integration, and data discovery”. And, all you have to do to be a part of that space is add a couple tags into your page.
Thanks to the following individuals for their time, assistance and insight: Michael Hausenblas, Ivan Herman, Eric Miller, Howard Greenblatt, Duane Degler, Marwan Sabbouh and Michel Biezunski.
Golda Velez (goldavelez.info) is a developer, consultant and freelance writer focusing on emerging technologies. She works on developing vocabularies for specialized domains and partnering with domain experts to create vertical sites. She lives with her husband and children in Tucson, Arizona.
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One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
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