Basics of the Semantic Web

We often get asked where to start with Semantic Web and RDF. There are probably many ways to do this and on this page you will find the one I found useful for myself. There is a lot of stuff to read so let us start with some basics first:

  • RDF Primer – This is a excellent introduction to RDF and the general concepts of the Semantic Web. Start here!
  • RDF can be serialized in many ways. If you start creating your first triples in a text editor you want to use Turtle serialization. If you are a programmer you might want to have a look at RDF/JSON and JSON-LD. The most popular one is probably RDF/XML but let your computer serialize that for you :) Don’t worry too much about that right now. If you can read Turtle you are ready for a good start.

Then it is time to do some hands-on stuff. I recommend to create a FOAF representation of yourself. Check some examples to get some hints: me (Adrian), Bart and ChristianTim Berners-Lee has a more advanced but also more complex one. You might want to create this with some help first and then adjust it according to the FOAF specification.

You might have noticed that our profiles are using RDF/XML serialization, which is not very easy to read. So let us transform that into something else:

Install Rapper on your system and convert the profile into Turtle. Use wget or curl to get my profile (assuming you are on MacOS/Unix):

curl -O

followed by a conversion from RDF/XML to Turtle:

rapper -i rdfxml -o turtle foaf.rdf > ktk.turtle

ktk.turtle now contains my FOAF profile in Turtle syntax.

If you now install Graphviz as well you will also get a binary called dot on your system. So try this:

rapper -i rdfxml -o dot foaf.rdf | dot -Tpdf -oktk.pdf

If you open ktk.pdf you should see a nice graph of my profile. If you then do that for your own FOAF profile you just bootstrapped your very own part of the Semantic Web. Congratulations!

It is now a good moment to upload your own file to your website, like we did with ours. Try to use a URI which stays there for as long as possible.

Now let us finish this introduction with some more reading:

  • The current web consists mostly of HTML documents. To add the expressiveness of RDF to HTML (or any other XML format) we can use RDFa which is specified at W3 as well.
  • As you can imagine your FOAF profile is one among billions of other pieces of information out there in the Semantic Web. The Linked Data Tutorial gives some more ideas about what you have to consider if you want to do that on a large scale.
  • If you have some more time you should read the book written by one of the authors of the Linked Data Tutorial called Linked Data: Evolving the Web into a Global Data Space.
  • And last but not least check out the Linked Open Data (LOD) cloud diagram (updated around once a year) and check how it evolved over the past few years ( 2007,  2008, 2009, 2010). Pretty impressive, right?

More in the next days!


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Or: How I Learned to Stop Worrying and Love the Next Web