Logic programming with integer or even floating point domains I am reading a lot about logic programming - ASP (Answer Set Programming) is one example or this. They (logic programs) are usually in the form:

[Program 1]
Rule1: a &lt;- a1, a2, ..., not am, am+1;
Rule2: ...

This set of rules is called the logic program and the s.c. model is the result of such computation - some kind of assignment of True/False values to each of a1, a2, ...
There is lot of research going on - e.g. how such kind of programs (rules) can be integrated with the (semantic web) ontologies to build knowledge bases that contain both - rules and ontologies (some kind of constraints/behaviour and data); there is lot of research about ASP itself - like parallel extensions, extensions for probabilistic logic, for temporal logic and so on.

My question is - is there some kind of research and maybe some proof-of-concept projects where this analysis is extended from Boolean variables to variables with integer and maybe even float domains? Currently I have not found any research that could address the following programs:

[Program 2]
Rule1 a1:=5 &lt;- a2=5, a3=7, a4&lt;8, ...
Rule2 ...
...
[the final assignment of values to a1, a2, etc., is the solution of this program]

Currently - as I understand - if one could like to perform some kind of analysis on Program-2 (e.g. to find if this program is correct in some sense - e.g. if it satisfies some properties, if it terminates, what domains are allowed not to violate some kind of properties and so on), then he or she must restate Program-2 in terms of Program-1 and then proceed in way which seems to be completely unexplored - to my knowledge (and I don't believe that is it unexplored, simply - I don't know some sources or trend). There is constraint logic programming that allow the use of statements with inequalities in Program-1, but it is too focused on Boolean variables as well. Actually - Programm-2 is of kind that can be fairly common in business rules systems, that was the cause of my interest in logic programming.

SO - my question has some history - my practical experience has led me to appreciate business rules systems/engines, especially - JBoss project Drools and it was my intention to do some kind of research of theory underlying s.c. production rules systems (I was and I am planning to do my thesis about them - if I would spot what can be done here), but I can say that there is little to do - after going over the literature (e.g. http://www.computer.org/csdl/trans/tk/2010/11/index.html was excellent IEEE TKDE special issues with some articles about them, one of them was writter by Drools leader) one can see that there is some kind of technical improvements of the decades old Rete algorithm but there is no theory of Drools or other production rule systems that could help with to do some formal analysis about them. So - the other question is - is there theory of production rule systems (for rule engines like Drools, Jess, CLIPS and so on) and is there practical need for such theory and what are the practical issues of using Drools and other systems that can be addressed by the theory of production rule systems.

p.s. I know - all these are questions that should be directed to thesis advisor, but my current position is that there is no (up to my knowledge) person in department where I am enrolled with who could fit to answer them, so - I am reading journals and also conference proceedings (there are nice conference series series of Lecture Notes in Computer Science - RuleML and RR)...

Thanks for any hint in advance!
The first question can be solved by googling integer logic programming.

http://en.wikipedia.org/wiki/Constraint_logic_programming

The second question is called the theory of expert programming. I was also able to google this.

http://en.wikipedia.org/wiki/Expert_system

There is a practical need for expert systems and rule based systems. They are used in many domains as you can see from here.

http://en.wikipedia.org/wiki/Expert_system#Examples_of_applications