OO Software desing handling constraints - which design pattern to use?

i have a question regarding software design. I think what im looking for is a well known problem and therefore there has to be a design pattern or a mix of patterns to solve it. But i cant figure it out.

Ok, heres the question. For example lets say that i have the following classes and properties:

CTask

• Name


• Duration


• TaskArea

CTaskArea

• Name

CPerson

• Name


• Abilities

CAbility

• Name

CTool

• Name


• CleaningTime

CConstraint

• Name


• Constraint

CTask, CPerson, CTool could have constraints e.g. Task A could only be done by persons with ability X, or person A could not do tasks of TaskArea X and so on. For example when i create a new CTask, CPerson or CTool i could imagine a constraint config dialog with dropdwons like:

Class | Operator | Class | Property | Value

CPerson | NOT | CTool | Name | Hammer

What is the best way to design this to have the opportunity to dynamically configure constraints for all the classes that could have constraints? I started looking at the observer pattern to have all the coinstraint capable classes registered, but i think there are better ways. What do you think?

Thanks in advance!

Tim