"Top Down" or "Bottom Up" Ontologies

I received the following question from a colleague of mine... He asked about the benefits and risks of using a single standardized ontology (a “top down” approach) versus using local, private, or community ontologies (“bottom up”). Unfortunately, the benefits of one are the risks of the other! A single standardized ontology admits no errors of translation or omission. However, consensus ranges from difficult to impossible to obtain, and usually many concessions have to be made during its definition. Local or community ontologies are natural, and admit no frustrations or human errors due to learning new representations, or due to using concepts that have little semantic meaning in a community. However, you typically have lots of community ontologies and need to interoperate between them.

What is a possible answer? Take the local, private and community ontologies of your business and map them "up" to an existing "standardized ontology" - such as exists in medicine or even construction - see, for example, ISO 15926. (I already discussed the possibilities of ontology alignment provided by the Semantic Web in earlier posts, and will provide more details over the next few weeks.)

Or, if a standard ontology does not exist, create one from the local ontologies by mapping the local ones to one or more "upper" ontologies. At this point, some people will say "ughhh" another term - "upper" ontology - what the heck is that? Upper ontologies capture very general and reusable terms and definitions. Two examples that are both interesting and useful are:

• SUMO (http://www.ontologyportal.org), the Suggested Upper Merged Ontology - SUMO incorporates much knowledge and broad content from a variety of sources. Its downside is that it is not directly importable into the Semantic Web infrastructure, as it is written in a different syntax (something called KIF). Its upsides are its vast, general coverage, its public domain IEEE licensing, and the many domain ontologies defined to extend it.
  
• Proton (http://proton.semanticweb.org/D1_8_1.pdf), PROTo ONtology - PROTON takes a totally different approach to its ontology definition. Instead of theoretical analysis and hand-creation of the ontology, PROTON was derived from a corpus of general news sources, and hence addresses modern day, political, financial and sports concepts. It is encoded in OWL (OWL-Lite to be precise) for Semantic Web use, and was defined as part of the European Union's SEKT (Semantically Enabled Knowledge Technologies) project, http://www.sekt-project.com. (I will definitely be blogging more about SEKT in future posts. There is much interesting work there!)

Now, I must be clear that I do NOT advocate pushing the standard ontology down to the local communities - unless there are only small tweaks to making the standard ontologies work there. With ontology alignment technologies, you can have the best of all worlds - a standard ontology to use when unifying and analyzing the local ontologies, but all the naturalness of the local ontologies for the communities.