Sunday, September 19, 2010

What is RDF?

I'm just getting started on a very interesting new class: Linked Data Ventures (6.898). It's all about the Semantic Web. I was familiar with the concept before, and have dealt with XML in the past in other contexts, but 6.898 really has us roll up our sleeves and get into the many other aspects of the technology, with the aim of student teams developing Semantic Web applications by the end of the semester.

In this post, I wanted to highlight a reading that pretty well sums up Resource Description Framework (RDF), one of the building blocks of the Semantic Web. It's one of these formats that many people have heard of, and sometimes associate with XML, but don't really know what it does. I know now:
Meaning is expressed by RDF, which encodes it in sets of triples, each triple being rather like the subject, verb and object of an elementary sentence. These triples can be written using XML tags. In RDF, a document makes assertions that particular things (people, Web pages or whatever) have properties (such as "is a sister of," "is the author of") with certain values (another person, another Web page). This structure turns out to be a natural way to describe the vast majority of the data processed by machines. Subject and object are each identified by a Universal Resource Identifier (URI), just as used in a link on a Web page. (URLs, Uniform Resource Locators, are the most common type of URI.) The verbs are also identified by URIs, which enables anyone to define a new concept, a new verb, just by defining a URI for it somewhere on the Web

Another important Linked Data concept that is cleanly defined in the article: Ontology, which is "a document or file that formally defines the relations among terms."

The article originally appeared in Scientific American, and was authored by James Hendler, Ora Lassila, and Tim Berners-Lee (who is one of the faculty teaching the class).

It's going to be an interesting semester . . .

More posts about my MIT Sloan Fellows experience:

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