UML Glossary

This glossary lists key terms and symbols used in UML data models (class diagrams), as discussed in Chapter 9.

Aggregate:

Class that is the “whole” in a whole-part relationship.

Association:

Relationship type, involving two or more association roles.

Association class:

An association that is also a class; an objectified association in ORM.

Association end:

Corresponds to a role in ORM.

Attribute:

Property of an object; either single-valued or multivalued.

Changeability:

How an attribute or role value may change: unrestricted, readonly, addOnly, removeOnly.

Class:

Type of object (cf. ORM entity type).

Collection property string:

Annotation to an attribute or association role indicating the kind of collection to be used. For example, {ordered}, {nonunique}, and {ordered, nonunique} specify an ordered set, bag, and sequence, respectively.

Composition

(composite aggregation): Each part belongs to at most one whole.

Data value:

Scalar constant; data type instance; self-identifying (cf. ORM value).

Derived element:

An attribute or association that is computed or inferred from others.

Generalization:

Forming a more general class (a superclass) from one or more classes.

Link:

Relationship instance—a fact in ORM.

Multiplicity:

Number of instances to which the same object may relate in an attribute or association.

Object:

A thing that may typically change its state; a class instance; identified by an oid (cf. ORM entity instance).

Oid:

Object identifier; system generated constant that references an object.

Qualified association:

Association where one class relates to another via a qualifier.

Shared aggregation:

A part may belong to more than one whole.

Specialization:

Forming one or more specific classes (subclasses) from a more general class.

State:

The properties of an object at a point in time.

Subset constraint:

Restricts the population of one association to be a subset of another.

Xor constraint:

Exclusive-or constraint between roles (association ends).