Web Service DescriptionsWhenever I design ontologies and the tools to use them, I find myself thinking that I should somehow be describing more, and having the computer do more of the work for me. Currently OWL is about describing general structure and relationships, but I keep feeling like ontologies should describe behavior as well.
I'm not advocating the inclusion of an imperative style of operation description here. If that were the case, then we'd just be building programming languages in RDF (something I've been thinking of for a while - after all, it seems natural to represent ASTs or List structure in RDF). I'm thinking more along the lines of OCL for UML. This is a far more declarative approach, and describes what things are, rather than how they do it. Like we were taught in first-year programming, OCL is all about describing the pre-conditions and post-conditions of functions.
The main problem I have with OCL is that it looks far too much like a programming language, which is the very thing I'd like to avoid. All the same, it's on the right track. It would be interesting to see something like it in OWL, though OWL still has a long way to go before it is ready for this. The other problem is that OCL is about constraining a description, which seems to be at odds with the open-world model in OWL.
Still, the world appears to be ready for OWL to have something like this, even if OWL isn't ready to include it. Maybe I should be building an RDF/Lisp interpreter after all? :-)
The reason for me thinking along these lines is that I'd like to be able to describe web services in a truely interoperable way. Today we have WSDL and OWL-S, which are very good at describing the names of services and how to interface to them, but do little to describe what those services do. If we could really describe a service correctly, then any client could connect into an unknown server and discover exactly what that server was capable of and how to talk to it, all without user interaction, and without any prior understanding of what that server could do.
Ultimately, I think this is what we are striving for with the Semantic Web. It is a long way beyond us today, but the evolution of hardware and software in computers over the last 60 years have taught us that amazing things are achievable, so long as we take it one step at a time.
To a limited extent, there are already systems like BioMOBY, which use ontologies to query about services, and can work out for themselves how to connect to remote services and connect them together to create entirely new functions. There are still assumptions made about what kind of data is there and how to talk to it, but it includes a level of automation that is astounding for anyone familiar with WSDL standards.
When I last saw BioMOBY nearly 3 years ago, they were using the own RDF-like data structures, and were considering moving to RDF to gain the benefit of using public standards. I should check them out again, and see where they went with that. They certainly had some great ideas that I'd like to see implemented in a more general context.