Expert system is based on three parts:
- A fact base,
- A rule base and
- An inference engine.
This engine will produce facts to answer a question.
PROLOG is based on an expert system.
It is a way to develop artificial intelligence system
The expert system can be used to make a chat room that will give interactive answer at some problems.

Keliasoft can offer modules based on expert systems
A need! What Keliasoft can offer me?