A Query Language for EER Schemas Michael Lawley Rodney Topor CRC for Distributed Systems Technology * and School of Computing and Information Technology Griffith University Nathan, Queensland 4111, Australia {lawley,rwt}@cit.gu.edu.au Abstract We present a proposed query language for extended entity relationship schemas. The language improves on previous proposals by using only concepts explicitly in a given schema. It includes quantifiers and aggregates to allow complex queries to be expressed, and it allows derived subtypes, attributes and relation- ships to be defined and used in queries. Further extensions are discussed. 1 Introduction The usual database design process is to design conceptual schema (e.g., an entity- relationship schema) which is then mapped into an implementation schema (e.g., a relational schema) for representation in a particular database management system. Application software, in particular queries, are then expressed in terms of the imple- mentation schema (e.g., using SQL). Why is this so? Why can’t the database designer avoid mapping the conceptual schema into the implementation schema, and write application software for the conceptual schema directly? In particular, why can’t casual users express queries in terms of the con- ceptual schema? This would avoid the mapping task and, more importantly, would allow users to express queries in more abstract, familiar, application-oriented terms. Presumably the reason is that there is no standard data manipulation language for conceptual schemas. * The work reported in this paper has been funded in part by the Cooperative Research Cen- tres Program through the Department of the Prime Minister and Cabinet of the Commonwealth Government of Australia.