5. Additional structural concepts

Tutorial on SDL-88
Belina, Hogrefe (edits Reed)

In the previous sections three main levels of detail have been used in a system definitions:

	system level,
	block level,
	process level.

In addition to the language constructs introduced so far, SDL-88 offers the following constructs for structuring a system description:

5.1 Block substructure
5.2 Channel substructure
5.3 Signal refinement

However, these features were not extensively used in SDL-88 (maybe because they were not well supported in tools). While they continued to be included in SDL-92, the were dropped in SDL-2000.