Pattern 16.15 Role Decoupling

Section 7.4 discusses package-level decoupling. Design patterns (such as Pattern 16.15, Role Decoupling, or Pattern 16.17, Observer) provide specific techniques for decoupling. 

Apply generalizations after you complete the basic design. A wide variety of design patterns are directed at generalization and decouphng. Most notable are Pattern 16.15, Role Decoupling and Pattern 16.16, Factories. 

Pattern 16.15, Role Decoupling, is used to minimize the Subject s dependence on the Observer. All it knows about is a type that can receive the update messages (see Figure 16.10). Several Observers can watch one Subject at a time. 

Move variation points into separate objects and have only one basic class of principal object (see Figure 16.11). Use Pattern 16.15, Role Decoupling, to keep the principal independent of the various plug-ins. 

Packages can be structured in many different ways. The separation of an interface from classes in separate packages provides a pattern for setting up the project package structure. Combined with consistent naming conventions, it makes certain aspects of the architecture very visible in the project development stmcture (see Section 7.4.1, Role-based Decoupling of Classes). 

Each type knows about the other (see Pattern 6.4, Refinement Is a Relation and Not a Sequence), something that is frequently represented using a two-way link. Although simple, this link often results in excessive coupling. A simple measure would be to decouple using types (see Section 7.4.1, Role-based Decoupling of Classes). 

Sun protection elements (aluminium and ETFE lamellae, or mobile textile membranes, cf. Fig. 6.6) can be integrated for further building-physics improvement in the clearance of dual-chamber systems with separate layers. In variants with a curved middle layer and decoupled volumes, and different pressures, the middle layer can assume the sun protection role. For this, the outer and middle foil layers display a print of inversely arranged patterns. The translucency of the cushions is controlled by adjusting the middle layer through pressure control of the two air-chambers. 

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