Information Modeling and Relational Databases, 2nd Edition

14.8. Reengineering

While conceptual modeling provides the best approach to developing new applications, it can also be used to remodel existing systems to better meet the requirements. There are three main reasons for replacing or revising (perhaps drastically) an existing information system.

First, the current system might provide an incorrect model of the UoD, either by being inaccurate (wrong information) or by being incomplete (missing information). Wrong or missing fact types, constraints, and derivation rules might arise because of bad modeling in the first place. For example, the schema might assert that planets orbit moons, allow people to have more than one birth date, or derive ages from a simple formula that ignores the extra day ...