Run-time composition of services: like a swan?

Web Services are a fairly amazing concept, when I think about it. You have a service, running on a server somewhere in the world, that accepts requests from other places and then returns information to them. This could be as simple as getting a request for the temperature in a particular city and returning it, or as complex as being asked to search a database for, say, hospitals near a given location, and return their details as an XML document.

Other people can then build onto that, combining different web services in various orders to get more and more detailed and crazy applications. This is what makes mobile development so exciting - there are so many possibilities open to creative designers that the sky isn't even the limit anymore.

What really begins to shake things up, though, is when there's more than one service offering the same results. There are likely to be a few factors separating them - one might cost more, yet one might be more reliable, and a third might return results more quickly.

So we start creating systems that look at the alternatives available when they query these services, in order to optimise the return of results - and that's not an easy task. And then we have to consider what happens when a particular service is unavailable - do we just wait and hope that it sorts itself out sooner rather than later, or do we try to recompose the rest of the service and attempt to get round the problem.

It's only as I dig deeper and deeper into the bowels of service composition that I realise how staggering a task it is - so many variables and so much frantic querying, estimating and processing, and all of this has to be hidden from the end user. It ends up like a swan: perfectly serene and stable on the surface, but flailing around like a mad thing underneath!

News at last

Finally there's a little bit of forward movement on the Masters course - we've got the dates for the seminars sorted. Of course, the first one is scheduled for one of the few days in the next few weeks where I have something on that cannot be cancelled or moved at all, but I guess that's life...

But at least there's stuff going on. In other news there, the collection of papers to do with SOA and the application of genetic algorithms thereto continues. There's been a bit more work done on this field than I'd anticipated, which was a little surprising, and it falls into two general streams.

One takes a composed service, made up of lots of interchangeable component services, and tries to work out the best combination of services given a specific set of requirements. This is pretty similar to work that I've done already in this area, so that's encouraging.

The second uses the genetic approach to try and combine services efficiently into a single component service. This looks fantastically interesting and useful, but it would mean learning a whole new mathematical language of combinatorial algebra, and then trying to code it into Java. Which is unlikely to take place over the course of a single, part-time year.

But hey - I'm meeting up with my supervisor soon enough, and we'll have a look through the papers to see if he thinks that the gaps I've spotted are (a) actually gaps at all and (b) big enough gaps for a research project.

Service composition

Electronic journals are both big and clever, it seems. It's also very useful to be working from within the library, and thus gaining instant access to said journals from my own laptop: technology is a marvellous thing!

I've started looking into service composition techniques now, and they're looking to be really quite a complex beastie, particularly when you begin to factor in dynamic service composition which, for my sins, is what I'm attempting to research. Obviously, when you have a group of x services that can e combined in a variety of orders to achieve a variety of results, searches to try and combine them are going to need to be heuristic to some degree: the mind-boggling number of combinations rapidly rules out a brute-force search for all but the smallest number of systems. However, the number of combinations and techniques available for a heuristic search is also beginning to hurt my brain ever so slightly.

Fortunately, it appears that not many people have looked into the method that I'd like to look at (genetic algorithms). Unfortunately, this means that I'll have to start this all from scratch!