UML Modelling and design class diagrams (For business logic?)

Hi all

I know this is a code forum, and this is not a code question, but i couldn't find better forum... I was hoping some of you could share your insight with uml diagrams.

I have a question regarding UML modelling, specifically with Design Class Diagrams.

I am in the process of modelling a system, and i need to know which classes i need to make design class diagrams for.

I have base classes such as "Customer" that stores the actual information like "First Name" etc. I also have business logic classes that hold the business logic relating to the customer component... e.g. search methods for finding customers etc.

Do i make "Design Class Diagrams" for the Business logic classes as well? and if so, what do i put down as attributes?