You can certainly go a long way with pretty naive models that take advantage of RDF[1][2], because you can just match words in a query to those in the ontology. Our model is a little more complicated, as we need to support everything from simple things like 'not' to negate part of a query, to more complex stuff like 'more recently', and compositional queries (what products have sold more than products that are red, tricky stuff like that).
[1]: http://gate.ac.uk/sale/dd/related-work/Kaufmann_nlp+reduce_E... [2]: http://gate.ac.uk/sale/eswc10/freya-main.pdf