Compound approximation spaces for relational data

• Compound approximation spaces for relational data are proposed.
• They are viewed as expansions of tolerance approximation spaces to a relational case.
• Properties of compound approximation spaces are investigated.
• Compound approximation spaces enable to derive new knowledge from relational data.

Rough set theory provides a powerful tool for dealing with uncertainty in data. Application of variety of rough set models to mining data stored in a single table has been widely studied. However, analysis of data stored in a relational structure using rough sets is still an extensive research area. This paper proposes compound approximation spaces and their constrained versions that are intended for handling uncertainty in relational data. The proposed spaces are expansions of tolerance approximation ones to a relational case. Compared with compound approximation spaces, the constrained version enables to derive new knowledge from relational data. The proposed approach can improve mining relational data that is uncertain, incomplete, or inconsistent.