APIfying COBOL Monoliths: Static Analysis with Pattern-Based Call Simplification

Legacy COBOL mainframes resist APIfication due to monolithic structure and scattered logic. We present a novel pipeline that extracts user-selected code blocks and generates \emph{compilable API modules with request/response copybooks}.

Key innovations include: (1) $\emph{five COBOL patterns}$ (P1--P5) guiding analysis selection, (2) $\emph{WoCC}$---a pattern-based call-chain approximation avoiding recursive traversal for organized monoliths, and (3) $\emph{end-to-end code synthesis}$ handling REDEFINES aliasing and inter-program calls.

Unlike prior slicing (variable sets only) or ADDI (read/write reporting), we deliver deployable APIs. On GENAPP/CBSA/industry systems, signature inference drops from weeks to minutes; refactoring effort reduces 15--50%. Practitioners validated precision; modules deployed via z/OS Connect pass functional tests.