Declaring a Concept

The 'concept' is the fundamental unit you can describe using SKOS Core.

An RDF description of a concept begins with something like the following:

<rdf:RDF 
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 
  xmlns:skos="http://www.w3.org/2004/02/skos/core#">
  
  <skos:Concept rdf:about="http://my.example.org/knowledgebase/biology#evolution"/>

</rdf:RDF>

It is worth noting that the above snippet of RDF/XML is the equivalent shorthand form of the following:

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
 
  <rdf:Description rdf:about="http://my.example.org/knowledgebase/biology#evolution">
    <rdf:type rdf:resource="http://www.w3.org/2004/02/skos/core#Concept"/>
  </rdf:Description>
  
</rdf:RDF>

In this guide, the shorthand form is used throughout for clarity.

Also note that the URI http://my.example.org/knowledgebase/biology#evolution is here an identifier for an abstract concept. It is not the URL of a document fragment.

For more on URIs for concepts, see the later section [ref concept URIs].

End section

Previous drafts ...

AJM first draft>

... defining a concept

SKOS Core talks about Concept and Concept Scheme. These terms were chosen because thesauri, terminologies, controlled vocabularies, glossaries etc. can all be modelled as consisting fundamentally of a set of concepts (i.e. ideas, notions). In this guide, Concept is used to refer to the fundamental unit of a thesaurus or controlled vocabulary, and Concept Scheme refers to a set of concepts, and including (optionally) a set of relationships between those concepts.

When it comes to using SKOS Core for things like blog category schemes and web directories, it get's a little hazy as to whether the fundamental units of these things should be called 'concepts' or not. ... @@TODO clarify ... If a thesaurus gets used in a similar way to a blog category scheme or a web directory, then it can be useful to treat their fundamental units in a similar way. So if it helps you to think of a blog category as a 'concept' then that's great. If it doesn't, don't worry about it.

I'm going to use a set of examples to illustrate how to use SKOS Core (and other vocabularies) to build up an RDF description of a concept and a concept scheme.

An RDF description of a concept begins with something like the following:

<rdf:RDF @@TODO XMLNS>
   <skos:Concept rdf:about="http://isegserv.itd.rl.ac.uk/topics/102"/>
</rdf:RDF>

This snippet of RDF/XML basically says '<http://isegserv.itd.rl.ac.uk/semwebtopics/102> is a skos:Concept'.

It is worth noting that the above example is in fact shorthand for the following:

<rdf:RDF>
   <rdf:Description rdf:about="http://isegserv.itd.rl.ac.uk/topics/102">
      <rdf:type rdf:resource="http://www.w3.org/2004/02/skos/core#Concept"/>
   </rdf:Description>
</rdf:RDF>

Throughout this guide, the shorthand form is used for clarity.