The Pragmatic Craftsman :: Simplicity from complexity ::

A critical ability in OO development is to skillfully assign responsibilities to software objects –Craig Larman author, Applying UML and Patterns

Can’t agree more with Larman. To be a good OO developer, to truly understand what object oriented means, you’ve got to treat classes as objects with responsibilities, and be knowledgeable on how to assign them. Larman’s book is classic in this category.

Here’s what Martin Fowler had to say on the subject.

Understanding responsibilities is key to good object-oriented design. –Martin Fowler quoted in Applying UML and Patterns