Subsystems do not exist, per se, in all software development environments. It is therefore the role of the user to establish a structure based on directories and files in order to implement them physically.
In this scheme, it is particularly judicious to use the subsystem concept as a means of integration, along with software analysis and design tools, compilation systems, and version and configuration management systems. Each subsystem is embodied by a directory that contains files. These files correspond to the different components included within the subsystem. The subsystem also contains the various files necessary for component compilation, documentation, and testing. The integration with compilation systems makes it possible to link the concept of the program library with that of the subsystem. The integration with a configuration management tool leads to building systems by combining compilation libraries. Integration may be still further enriched by a version manager, ideally with two levels of granularity. It then becomes possible to build a system by combining versions of subsystems (expressed as program libraries), that are themselves composed of component versions.
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