Understanding natural programs using proper decomposition

The author presents a practical method for automatic control concept recognition in large, unstructured imperative programs. Control concepts are abstract notions about interactions between control flow, data flow, and computation, e.g., read-process loops. They are recognized by comparing a language-independent abstract program representation against standard implementation plans. Recognition is efficient and scalable because the program representation is hierarchically decomposed by propers (single entry/exit control flow subgraphs). A recognition experiment using the UNPROG program understander shows the method´s performance, the role of proper decomposition, and the ability to use standard implementations in a sample of programs. How recognized control concepts are used to perform Cobol restructuring with quality not possible with existing syntactic methods is described