2004-11-22

Tom Gruber on ontologies

Danny Ayers cited that interview (linked under the Title above), and posted this quote, which I have extended, and which, I think, is appropriate to any discussion about object identity. I am not sure what to make of the comment about state, but it sounds like he's making a case for a RESTful architecture. I leave that up for comments.
In fact, the World Wide Web is based on a semiformal ontology, and it shows how ontological commitment works in software interoperability. At its core, the concept of the hyperlink is based on an ontological commitment to object identity. In order to hyperlink to an object requires that there be a stable notion of object and that its identity doesn’t depend on context (which page I am on now, or time, or who I am). Most of the machinery of the early Web standards are specifications of what can be an object with identity, and how to identify it independently of context. These standards documents serve as ontologies - specifications of the concepts you need to commit to if you want to play fairly on the Web. If one built a system with these committments, all of the Web infrastructure works well. If you violate the spirit of the ontology - such as the agreement on identity - things don't work so well. For example, early Web servers often packed a lot of state into the URLs, which violated the notion of object identity. Systems built this way could not be searched, bookmarked, or mentioned in email messages. I think that there were design weaknesses in the ontologies - ambiguities in the standards documents - that allowed formal compatibility with the Web without a committment to the conceptualization on which it is based.