Summary.
Details about Domain Classes
- Attribute
- Describes one piece of info about each instance of the class
- Identifier or key
- One attribute uniquely identifies an instance of the class. Required for data entities, optional for domain classes. Customer ID identifies a customer (E.g, broncoID)
- Compound attribute
- Two or more attributes combined into one structure to simplify the model (e.g, address rather than number, street, city, etc.). Sometimes an identifier or key is a compound attribute (1 attribute)
- 5 text boxes for address instead of 1 compound address text box
- Instead of having a sectionID key as a foreign key when linking a Course class with Section class, we can eliminate that sectionID in place of a compound key that uses the CourseID column with the SectionNum column to make a unique identifier for each row.
- Two or more attributes combined into one structure to simplify the model (e.g, address rather than number, street, city, etc.). Sometimes an identifier or key is a compound attribute (1 attribute)
Association Among Things
- Association
- A naturally occurring relationship between classes (UML term)## Types of Associations
- Binary Association
- Associations between exactly two different classes
- Unary Association (recursive)
- Ternary Association (three)
- N-ary Association (between n)
Comments