Paul Miller has kicked off a twitstorm with his simple question: <a href="http://cloudofdata.com/2009/07/does-linked-data-need-rdf/">does linked data require RDF?</a>. My contention is that Linked Data does absolutely require RDF. This is not a technical issue and its not one of zealots or pragmatists: its a marketing and branding issue.

The term Linked Data was coined to brand a specific class of practices: namely assigning HTTP URIs to abitrary things and making those URIs respond with RDF relating the things to other things.

Here very few of the ’things’ are documents, instead they are people, places, objects and concepts.

That deliberately excludes many other practices of publishing data on the web such as atom feeds, spreadsheets, APIs and even many existing RDF use cases.

The purpose of giving things a brand is to engender recognition, familiarity and trust. When you open a can of Pepsi you know exactly what you are going to get. You know you will get a great user experience whatever Apple product you buy. When you buy Lego you can rely on all the pieces fitting together.

The Linked Data brand makes similar promises of quality and consistency. When you consume Linked Data you know it will be RDF so your tools will work correctly. You also know that the data will be using HTTP URIs to refer to real-world things so you can determine what the data is about. You can trust that you’re not suddenly going to be given some XML in a proprietary schema or CSV with text headings you will have to guess the meaning of.

The Semantic Web community has been notorious for its poor marketing over the past decade. Now just when it seems the community has found the right balance between technology and mass appeal it feels like people are trying to rip away that success for their own purposes. That is deliberately emotive language because brands are all about emotion.

I don’t want to see the Linked Data brand weakened because it destroys trust. That’s why I pushed back on Twitter. As all involved know I am a huge advocate of making more data available on the web for reuse. It makes me glad whenever I see people invest their time in publishing data in any format, but my heart sings when I see more Linked Data.

There are many situations where there are better approaches than Linked Data e.g. I would rather have a midi file than the RDF version. In many circumstances I would be glad of a spreadsheet - simple and convenient.

But we should not confuse these forms of data publishing with Linked Data. That would sow confusion and be counterproductive. The coming web of data will be a rich and varied space full of content and data in every format imaginable. A large part of that we will call Linked Data and when you encounter it you will be justified in expecting RDF and HTTP.

I welcome anyone who wants to share data on the web in any way. But play fair and use the Linked Data brand only when it uses the Linked Data rules.