What the Heck is an Ontology? (in PDF format) "There's no doubt about it; ontologies are on the up. The ideas are gaining wider acceptance and these days you're much less likely to be greeted by that familiar baf ed expression of those who are too afraid to ask what the heck you are talking about. Tools like Protege (http:// protege.stanford.edu/)continue to improve in robustness, and extend their functionality; and there are new tools on the scene too,such as SWOOP (http://www.mindswap.org/2004/SWOOP/) and Haystack (http://haystack.lcs.mit.edu/index.html)."
"Perhaps the hardest technical challenge is using ontolo-gies to enable the ad-hoc reuse of existing software com-ponents. In other words, it is much easier to design a suite of programs that all commit to the same ontology than to coerce existing programs to communicate effectively."