Is it perfectly alright to refer a category resource in an ontology by using wikipedia URI? Like http://en.wikipedia.org/wiki/Category:Cuisine for Cuisines? I want to define user interests using FOAF such as:
<foaf:topic_interest>Cuisines</foaf:topic_interest>
I'm a beginner, just want to know is it possible to make this association with wikipedia? And if yes then what's the syntax? and if not then what other option do I have?
You can make the association you suggest like this (assuming this is placed in the right place in a valid document):
<foaf:topic_interest>http://en.wikipedia.org/wiki/Category:Cuisine</foaf:topic_interest>
However, it would be more useful to link it to DBPedia. DBPedia extracts data from Wikipedia as RDF. The DBPedia wiki contains an example on how to link FOAF to DBpeida URIs. Thus, the example in your question would look like this:
<foaf:topic_interest>http://dbpedia.org/page/Cuisine</foaf:topic_interest>
With the link representing a dereferenceable RDF description of the URI.