ARCHITECTURAL STYLES

1.architectural styles
the builder has used an architectural style as a descriptive mechanism to differentiate the house from other. the software that is built for computer-based systems also exhibits one of many architectural styles. each style describes a system category that encompasses
(1) a set of components (e.g., a database, computational modules) that perform a function required by a system
(2) a set of connectors that enable “communication, coordinations and cooperation” among components
(3) constraints that define how components can be integrated to form the system
and (4) semantic models that enable a designer to understand the overall properties of a system by analyzing the known of its constituent parts . in the section that follows, we consider commonly used architectural patterns for software:-
a brief taxonomy of styles and patterns
although millions of computer-based systems have been created over the past 50 years, the vast majority can be categorized into one of a relatively small number of architectural styles:
data-centered architectures.
a data store (e.g., a file or database) resides at the center of this architecture and is accessed frequently by other components that updating, add, deleting, or otherwise modify data within the store. figure 14.1 illus- trates a typical data-centered style. client software accesses a central repository. in some cases the data repository is passive. that is, client software accesses the data independent of any changes to the data or the actions of other client software. a variation on this approach transforms the repository into a “blackboard” that sends notifications to client software when data of interest to the client change.


data-centered architectures promote integrability. that is, existing components can be changed and new client components can be added to the architecture without concern about other clients (because the client components operate independently). in addition, data can be passed among clients using the blackboard mechanism (i.e., the blackboard component serves to coordinate the transfer of information between clients). client components independently execute processes.