Thanks,
Russell
There are multiple kinds of rule engines: logic programming,
production rules, etc and multiple semantics for logic programming.
Maybe you should start from the Wikipedia page for logic programming,
Prolog, production rule systems, well-founded models, stable models
and answer set programing, and then proceed through the links in the
references. I can post some links below, but I don't know how helpful
they might be for you. Try the Wiki pages first for the sentences
above and you may find what you need.