Instructors' Guide

1. I suggest taking the example described in section Drawtool, but you are encouraged to find a different example.
2. See slide class-design.
3. Class invariants may be disrupted by refining methods that introduce hidden modifications to the value(s) of instance variables. See section class-invariants.
4. The intuition underlying the Law of Demeter is essentially that ignorance of how a class is implemented is beneficial for understanding and maintenance. See section Demeter.
5. See slide Demeter.
6. Semantic modeling is mostly concerned with defining the attributes of objects and the relation between object classes. Object-oriented modeling, in contrast, is more concerned with characterizing the behavioral properties of objects. However, the two approaches are converging.
7. Abstract systems may be regarded as the characterization of the functionality offered by a collection of abstract data types. It specifies the repertoire of methods available to the user of such a collection.
8. Classes corresponding to actual events specify the interactions which must occur between objects. The resources which are needed when the event occurs are specified when creating the event. Protection is offered by hiding the interaction between the objects in the definition of the event activation operator.