Model management with a large number of models has placed demands on a highly structured and rigorous framework. The paper proposes a new framework, called the RASES (Relational Algebraic System Entity Structure), for model management: it is based on the concepts of system entity structure (SES) and relational algebra (RA). SES is accepted as a conceptual basis to organize a family of hierarchical structures of models. Under the RASES, SES itself is represented in the form of relations which may be stored as tables in a relational database. Furthermore, several operations on SES can be formulated in terms of relational algebra which can be coded in a standard query language.