Using Program Transformations to Add Structure to a Legacy Data Model

An appropriate translation of the data model is central to any language migration effort. Finding a mapping between original and target data models may be challenging for legacy languages (e.g., Assembly) which lack a structured data model and rely instead on explicit programmer control of the overlay of variables. Before legacy applications written in languages with an unstructured data model can be migrated to modern languages, a structured data model must be inferred. This paper describes a set of source transformations used to create such a model as part of a migration of eight million lines of code to Java. The original application is written in a proprietary language supporting variable layout by memory relocation.