Another common use case is product configuration where you need to fit different parts into a compatible whole. For example, "I already have Machines A and B w

Another common use case is product configuration where you need to fit different parts into a compatible whole. For example, "I already have Machines A and B with control system S, but now I want to add Machines C and D from another vendor and I need the control systems to work together, what are my options?" It would query the configuration rules about products and compatibility with the 'knows' that you tell it and find options for the 'unknowns' and tell you something like, "then you can buy X, Y or Z, but if you chose Z you also need to buy an external temperature control from the Foobar 800 series with the D-bus adapter". In practice, it is often even more complex. Logic programming is great for this, and I find that using it in small subsystems of a larger application is a super powerful tool. For interactive systems, a fast implementation is really important. The CLP aspects of Scryer Prolog would also be very helpful.