Presentation, abstraction, control
The Patron of design CAP was introduced by the enquiring one in Grenoble-native data processing Joelle Coutaz into the years 1980 as an abstract model of software Architecture for the man-machine interfaces. It stipulates that an interactive software can be organized like a hierarchy of components made up each of three facets:
- the Presentation deals with the interaction with the user, for example by posting a drawing and by managing the entries carried out with the mouse. The whole of the facets of Presentation constitutes the part of the program purely dedicated to the IHM.
- the Abstraction manages the data to be represented, or the functions to be interfaced. It is for example, in a cellphone, the address book and the management of the telephone calls. The whole of the Abstractions is the part which formerly constituted the totality of the programs, and which one now calls the functional core.
- control manages the correspondence between the two other facets: coherence of the representations with the internal data, conversion of the actions of the user into operations of the functional core. The facets of control are also used to create a hierarchy of software components to organize the program: the facet of control of the component relative communicates with that of the component wire.
CAP is an abstract model which does not describe in which form must be realized and connected the various facets. Various solutions were implemented by the programmers, by using for example the heritage or of constructions containing pointers.
CAP is sometimes confused, by error, with the owner Model-Sight-Controller (MVC) introduced in 1979 around the Smalltalk language. CAP is directed much more towards separation between IHM and functional core, therefore worms of the objectives of software genius. MVC is focused more on the organization of the entries and the exits in the software components. To note besides that the " Contrôle" CAP is very different from the " Contrôle" from MVC: first has as a role to control (“control”) the coherence of the software facets between them, the second manages the entries of the user and of this fact allows him to control (“control”) the execution of the program. Certain recent interpretations of MVC are closer to CAP than work of origin on MVC.