Extracting entity-relationship diagram from a table-based legacy database

Current database reverse engineering researches presume that the information regarding semantics of attributes, primary keys, and foreign keys in database tables is complete. However, this may not be the case. In a recent DBRE effort to derive a data model from a table-based database system, we find the data content of many attributes are not related to their names at all. In this paper, we present a process that extracts an extended entity-relationship diagram from a table-based database with little descriptions for the fields in its tables and no description for keys. The primary inputs of our approach are system display forms, table schema and data instance. We utilize screen displays to construct form instances. Secondly, code analysis and data analysis involving comparisons of fields and decomposition of fields are applied to extract attribute semantics from forms and table schemas, followed by the determination of primary keys, foreign keys and constraints of the database system. In the final step of conceptualization, with the processes of table mergence and relationship identification, an extended ER diagram is successfully extracted in a case study.