Hierarchical Composition of Architecture Styles
A natural way to compose styles when different functional pieces of the system
are best developed using different styles is what we will call hierarchical
composition. What this amounts to is the development of a higher-level
style that explains how data and control are exchanged between the styles used
in different major subsystems. The different functional components in
diagrams drawn using this higher-level style are internally developed using
different styles. The figure below illustrates this for a
flight management system architecture. High-level subsystems such as
navigation, which process time-varying signals, may be developed using a block
diagram style such as that provided by the
ControlH architecture specification language
. Functional subsystems such as Electronic Flight Instrument
Systems (EFIS), which manage cockpit displays, may be developed using an
object-oriented style. At the higher level, specific styles and interface
guidelines are developed to allow these components to interact as needed. For
example, the higher-level diagram may use a real-time process style,
such as that provided by the
MetaH architecture specification language
.
Output signals within the navigation component might be obtained using service
calls to an interface object within the EFIS component. Sometimes the overall
coding guidelines may call for various kinds of special interface or
translation code to be written.
