A little fyi/progress report.

For a couple of years now I’ve been mooching around refactoring the intelligent agent paradigm to cover (RESTful) Web services. The kind of intelligence I have in mind is potentially, well, non-existent : a regular Web site could be considered an agent. The motivation is mostly that developing spec-compliant systems on the Web is in general a lot of work, and that this leads to either cutting corners/breaking specs or using frameworks that limit one’s opportunities for innovation. When we introduce Semantic Web technologies into the mix, things get even more difficult.

So what I was after was a simple abstraction of (Semantic) Web systems/services that would allow a lot of the gruesome details of implementation to be hidden away, without breaking the Web. What I came up with looks like this:

An archetypal agent would feature (access from) a HTTP server and a local HTTP client for input & output, a local RDF model for its working memory along with some kind of business logic (behaviour) that would determine what it actually did. (I’m putting on hold one of the usual features of intelligent agents – mobility – though a story on this would be nice for issues like scalability). Agents are effectively self-contained, event-driven components with a common interface (HTTP).

A regular Web site could fit this abstraction in a degenerate form: no HTTP client, content is held in a persistent model, the behaviour is just to deliver that content to any other agents that make appropriate requests (in this case those other agents would typically be browsers, well-known degenerates).

In the past I must confess I’ve tried to express this stuff via MVC, which was a bit of a stretch – I agree with Ian’s view that this isn’t really appropriate for the Web. RMR, ROA or WOA (take your pick!) is a much better fit. Having said that, I’m not sure how much the developer should be operating on the level of resources and representations, they seem more like bricks and cement than architecture – e.g. conneg and httpRange-14 303s should Just Work.

So now (or rather, quite a while ago) I needed a proof of concept system that would allow easy construction of this kind of agent, and I spent a good many free-time hours putting together a little framework. The way I was approaching it (in Java) was for the framework to provide a container for agents, and those agents being aware whether or not they were in the same container. If they were, they could address each other directly, while still supporting HTTP I/O for communications otherwise.

I got quite a long way, despite hitting numerous snags (incorporating asynchronous eventing into the HTTP request/response cycle was a good one). But then as of a few months ago didn’t have much opportunity to look at this stuff.

Fast forward to a few weeks ago. In my todo queue was getting down deep with OpenID and OAuth (which I’m familiar with but haven’t really stress-tested), and it was hard not to imagine using the agent approach to play with these components. Coincidentally I went up to visit Reto in Switzerland and the company he now works for – Trialox who are (amongst other things) building a Semantic Web CMS. While I was up there, Reto gave me an intro to OSGi (formerly the Open Services Gateway initiative) which is essentially a set of specs for a Java-based service platform – it’s used in Eclipse, for example. Somewhat bizarrely I think I missed out on learning about this previously because I must have glazed over when seeing the acronym, confusing it with OGSI (the Open Grid Services Infrastructure).

To cut a long story marginally shorter, I’ve now ditched my own agent framework code (I can no doubt recycle bits) in favour of OSGi, and am currently noodling with creating the appropriate bundles – as OSGi calls its components – for the agent stuff, using Apache Felix as the host framework. I’ve still a good way to go before I get to my proof of concept, but after only a couple of days learning/coding I’m already making much more rapid progress than I was with my own ad hoc stuff. With a bit of luck I’ll have testbed stuff together for OpenID & OAuth (and related setups like FOAF+SSL) within the next week or so. I’m obviously also going to be looking at hooks into the Talis Platform. I can’t remember offhand whether it was Ian, Leigh or Sam, but someone’s already put together a load of Java client code to wrap HTTP interactions with the Platform, so most of the work there’s already been done.

Oh yeah, and I reckon OSGi might well give me a neat approach to the Semantic Web in a Box.

[Work in progress is currently in my personal svn://hyperdata.org/svn/ but I'll move it into the n² svn once I've got something more functional].