7.2. Selection Expressions

Actions can operate on one or more objects in the domain. We use selection expressions to select single objects or sets of objects. The result of a selection expression is an object reference set.

Definition: An object reference set holds a set of object references.

The extent of a class is its current set of objects. (A set is a mathematical term that means some number (possibly zero) of distinct elements. A class extent is always a set because the objects of a class are defined to be distinct.)

Figure 7.3 shows actions and concepts related to object selection, and several examples are shown in Figure 7.4. The first statement gets the extent of all books, and the object reference set books refers to the current set ...

Get Executable UML: A Foundation for Model-Driven Architecture now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.