I’ve recently had to defend my position supporting the construction of an overall (uber-, super-, ultra-, mega-) ontology for internal use at my company.

The argument goes something like this: building an all-encompassing, monolithic ontology is a time-consuming, academic exercise with end results which do not justify the effort. Rather than build something so complicated, instead create multiple taxonomies which are specific to the use to which you want to apply them. On the surface, not an unreasonable argument. However, there are several suppositions built into this.

First, you will never mix your content, therefore you will not have to deal with term conflicts arising from multiple taxonomies covering potentially mutually exclusive or overlapping concepts.

Second, you will never have to worry about conflict resolution between taxonomies.

Finally, complicated relationships involved in ontology construction are pervasive within your vocabulary and require rule-building for each and every term.

In my experience, it’s whether you want to suffer the migraine for a shorter period of time or deal with persistent headaches without end. While neither taxonomies or ontologies are ever finished, they do arrive at a place where there is less construction and more maintenance. While an ontology requires a very large up-front construction effort, the maintenance thereafter is not particularly difficult (working on the assumption that your foundation was sound). Contrary to some notions, an ontology does not require laborious rule writing. Save that effort for when you truly can’t resolve conflicts.

The same goes for taxonomies. However, when your content begins to mix, you will have conflicts. The more mixing, the more conflict resolution between terms. These can cascade into the realization that your separate taxonomies are incompatible. I’ve worked on many more projects requiring the creation of one taxonomy or ontology from many taxonomies than the other way around.

Yes, the idea that you’ll build the ontology to cover all topics is ludicrous, but they can be built from the ground up in such a way as to cover your domain and be flexible enough to include new areas. Like anything else, planning a good, all-encompassing ontology is difficult while creating taxonomies “on the fly” or at least in short order based on new content is much easier. What you get, however, is sprawl and conflict which negates the short-term win of an easy build.

Give me one migraine over multiple headaches if I have the choice.