The structured design of a data compression program

A program which performs adaptive optimal data compression has been implemented using Jackson's Structured Design Methodology. The design process is discussed at the level of partitioning the program into tractable blocks and using a typical block, at the level of comparing data structures and program structures. Ideally the structure at these levels of generality is independent of execution and machine considerations. However, such considerations do affect the high levels of structure in this program. This "structure corruption" is detailed.