Technical forum: Using logical data models for understanding and transforming legacy business applications

Show me your flowchart and conceal your tables, and I shall continue to be mystified. Show me your tables, and I won't usually need your flowchart; it'll be obvious. Frederick Brooks, The Mythical Man-Month Modifying a legacy application is typically an expensive and time-consuming process, even when the required modifications are conceptually very simple. We argue that this problem can be ameliorated by adopting an approach in which logical data models of a legacy application are used by software developers to understand, maintain, and transform the software. In addition, we outline the goals and status of the Mastery project at IBM Research, which aims to build a suite of tools for automatically extracting logical models from legacy applications, focusing initially on logical data models. THE PROBLEM For the past few years, our group at IBM Research has been investigating tools and techniques for analyzing and transforming legacy business applications , focusing on mainframe-based applications written in COBOL. 1 Such applications are often decades old and implement core business function-ality. Yet they are difficult to update in a timely manner in response to new business requirements due to a number of factors that include the following: Volume of code in a typical application Logical structure of code has deteriorated as updates have accumulated over time Functional redundancy Structure of code reflects the dated technology on which it was built Scarce technical skills Size Legacy application portfolios, that is, complete collections of programs and related components,