This post was prompted by this tweet from Tim O’Reilly…
People learning about Linked Data frequently ask “what’s the relationship between Linked Data and the Semantic Web?”, which is a fair and good question. One of the responses that crops up relatively frequently is that Linked Data is just an attempt to rebrand the Semantic Web. In my experience these kind of rebranding comments come mostly from people who have a certain impression of the Semantic Web vision (which may or may not be accurate), don’t like this vision, and therefore dismiss Linked Data on this basis without actually considering what it means (i.e. a means to dismantle data silos), and without necessarily rethinking their original view of the Semantic Web concept. I prefer to see it this way…
Think about HTML documents; when people started weaving these together with hyperlinks we got a Web of documents. Now think about data. When people started weaving individual bits of data together with RDF triples (that expressed the relationship between these bits of data) we saw the emergence of a Web of data. Linked Data is no more complex than this – connecting related data across the Web using URIs, HTTP and RDF. Of course there are many ways to have linked data, but in common usage Linked Data refers to the principles set out by Tim Berners-Lee in 2006.
So if we link data together using Web technologies, and according to these principles, the result is a Web of data. Personally I use the term Web of data largely interchangeably with the term Semantic Web, although not everyone in the Semantic Web world would agree with this. The precise term I use depends on the audience. With Semantic Web geeks I say Semantic Web, with others I tend to say Web of data – it’s not about rebranding, it’s about using terms that make sense to your audience, and Web of data speaks to people much more clearly than Semantic Web. Similarly, Linked Data isn’t about rebranding the Semantic Web, it’s about clarifying its fundamentals.
Tim Berners-Lee said several times last year, in public, that “Linked Data is the Semantic Web done right” (e.g. see these slides from Linked Data Planet in New York), and who am I to argue, it’s his vision. But to see this as a recent trend or a u-turn ignores the historical context. On page 191 of my copy of Weaving the Web (dated 2000, ISBN-13: 9781587990182) it says:
The first step is putting data on the Web in a form that machines can naturally understand, or converting it to that form. This creates what I call a Semantic Web – a web of data that can be processed directly or indirectly by machines.
I’m not sure this quote adequately captures the importance of links in the whole picture, but no one can claim that the Web of data label is recent marketing spin invented to make the Semantic Web palatable. This was always the deal. It’s certainly how I understood the concept (and what inspired me to do a PhD in the area).
If othersÂ have somehow diverted the Semantic Web vision down some side road since Weaving the Web was written, then that’s unfortunate. (In my experience the Linking Open Data project was an attempt to reconnect the Semantic Web community with the some of the key aspects of the original vision that were being overlooked, like having a real Web of data as the basis for research). I certainly notice plenty of unjustified attempts at present to co-opt the term Semantic Web, now that it’s no longer a dirty word, and drive it off down some dodgy alleyway. Some of these products, services or companies may be applications or services that use some semantic technology and are delivered over the Web, but that doesn’t make them Semantic Web applications, services or companies. Anything claiming the Semantic Web label needs to get its hands dirty with Linked Data somewhere along the way. That’s just how it is.
So to return to Tim O’Reilly’s tweet, he’s not far wrong about the lack of difference between Linked Data, Semantic Web and RDF (we’ll ignore the means vs end vs technology distinction), but I’d love to know who he’s quoting about the explicit rebranding.