6.2. Basic Set Theory
Since the constraints in step 6 make substantial use of sets and set operations, let’s first review some basic set theory. To provide a comprehensive summary of the required background, some ideas met earlier are included.
Intuitively, a set is a well-defined collection of items. The items may be concrete (e.g., people, computers) or abstract (e.g., numbers, points) and are called elements or members of the set. Sets themselves are abstract. They are numerically definite in the sense that each has a definite number of elements. A type is a set of possible items, understood as sharing some common characteristics (possibly unstated).
The members of a set collectively constitute the extension of the set. While a set may
Get Information Modeling and Relational Databases, 2nd Edition 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.
