Nowadays, the vast volume of collected digital data obliges us to employ processing methods like pattern recognition and data mining in order to reduce the complexity of data management. The output of these techniques are knowledge artifacts, heterogeneous in both structure and semantics. We claim that the concept of pattern is a good candidate for generic representation of these novel information types. The PANDA project is aimed at studying the main issues related to pattern handling. In this paper we present the preliminary results obtained: we outline the architecture of Pattern-Base Management Systems, we provide the foundations of the logical framework, and we present the preliminary issues related to processing queries on patterns.