[ses]

I think Prolog still has a place in modern software development. It provides a natural way of carrying out a backwards chaining depth first search through a state space (good for game AI, planning and scheduling etc). Also constraint solving is a very useful feature built into most logic programming languages now.

Prolog pureists argue that the whole of Prolog can be used for applications, but I tend to take a different approach that integration of Prolog with other languages can help you to do the things its really good and you can get the best out of multiple languages.

That's why I developed a (now open source) platform for integrating Prolog with other applications via web services... see http://kms.intelligent-architectures.co.uk/

[jethroalias97]

I'm a logic fan so I like prolog a lot, though for many people admittedly its greatest attribute will be expanding the way you think about programming.

However for some problems you might want to go right to constraint programming as you mentioned if you need speed and ease of modeling. I like MiniZinc for many problems, or if you're interested you could try my constraint programming language (http://sabrlang.org) which is based on spatial and temporal logic.

[kunley]

+1 for the pragmatic use of Prolog.

One can have Prolog-as-a-service. The SWI-PL implementation has excellent webserver out of the box. We feed the Prolog database from some external sources, do the reasoning and expose results via dead simple JSON API. It Just Works (tm) !!