Information Technology Reference
In-Depth Information
Class User
Call Class
Realize Class
Class Implementor
Developer
Class Extender
Refine Class
Fig. 8.5
Class Implementor, Class extender, Class user role
constraints on the services provided by the specialized class. Figure
8.5
shows the
role of each of the above described developers in class implementation.
8.5.2 Object Constraint Language
The Object Constraint Language (OCL) is a notational language for the analysis
and design of software systems. It is a subset of the industry standard Unified
Modeling Language (UML) that allows software developers to write constraints
and queries over object models. These constraints are particularly useful, as they
allow a developer to create a highly specific set of rules that govern the aspects of
an individual object. As many software projects today require unique and complex
rules that are written specifically for business models, OCL is becoming an inte-
gral facet of object development. The Object Constraint Language (OCL) is a
language that enables one to describe expressions and constraints on object-ori-
ented models and other object modeling artifacts. An expression is an indication or
specification of a value. A constraint is a restriction on one or more values of (or
part of) an object-oriented model or system. Various constraint languages have
been used in object-oriented modeling methods (Syntropy, Catalysis, and BON),
and programming languages (Eiffel). The OCL is a standard query language,
which is part of the Unified Modeling Language (UML) set by the Object Man-
agement Group (OMG) as a standard for object-oriented analysis and design.
