Establishing referential integrity in legacy information systems - Reality bites!

Most modern relational DBMS have the ability to monitor and enforce referential integrity constraints (RICs). In contrast to new applications, however, heavily evolved legacy information systems may not make use of this important feature, if their design predates its availability. The detection of RICs in legacy systems has been a long-term research topic in the DB reengineering community and a variety of different methods have been proposed, analyzing schema, application code and data. However, empirical evidence on their application for reengineering large-scale industrial systems is scarce and all too often "problems" (case studies) are carefully selected to fit a particular "solution" (method), rather than the other way around. This paper takes a different approach. We analyze in detail the issues posed in reengineering a complex, mission-critical information system to support RICs. In our analysis, we find that many of the assumptions typically made in DB reengineering methods do not readily apply. Based on our findings, we design a process and tools for detecting RICs in context of our real-world problem and provide preliminary results on their effectiveness.