Learning UML

Properties

A property is a characteristic 1of a model element. Use properties to define attributes and rules for a given type of modeling element. For example, properties can define the following: attributes representing a project’s start and end dates, a specific textual description of the relationship between a project and the things that make up the project, and a rule that the start date must precede the end date.

Properties are shown as a comma-delimited list of text strings inside a pair of braces ({}) after or below the name of a model element. Each property may be expressed in any natural or computer language. Each text string may be a tag or constraint, both of which are discussed in the next sections.

Tags

A tag is an attribute of a model element and its corresponding value — for example, attributes representing a project’s start and end dates.

Defining tags

In the UML, you create a tag definition when defining a stereotype by showing a name for the attribute, called a keyword, followed by a colon followed by the type of the attribute. The tags defined for a stereotype apply to each model element to which the stereotype is applied.

For example, Figure 9-4 updates Figure 9-1 and shows a tag named Start Date (which is a string representing a project’s start date), a tag named End Date (which is a string representing a project’s end date), and a tag named Descripton (which is a string representing a description of the relationship between a project and a thing that makes up the ...