The 'Gang of Four' Companion:

Bridge Design Pattern

Formal specification of design patterns in LePUS3 and Class-Z

This page is part of the The 'Gang of Four' Companion dedicated to the formal specification in LePUS3 and Class-Z of patterns from the 'Gang of Four' catalogue [Gamma et al 1995].

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The Bridge design motif

The informal description: Excerpts from [Gamma et al. 1995] (adapted for this purpose):

Intent: Decouple an abstraction from its implementation so that the two can vary independently.

Structure: Original OMT diagram converted to UML (Why and How?):

Participants:

Abstraction: defines the abstraction's interface and maintains a reference to an object of type Implementor.
RefinedAbstraction: Extends the interface defined by Abstraction.
Implementor: defines the interface for implementation classes. This interface doesn't have to correspond exactly to Abstraction's interface; in fact the two interfaces can be quite different. Typically the Implementor interface provides only primitive operations, and Abstraction defines higher-level operations based on these primitives.
ConcreteImplementor: implements the Implementor interface and defines its concrete implementation.

Collaborations: Abstraction forwards client requests to its Implementor object.