Current theoretical work offers measures of schema equivalence based on the information capacity of schemas. This work is based on the existence of abstract functions satisfying various restrictions between the sets of all instances of two schemas. In considering schemas that arise in practice, however, it is not clear how to reason about the existence of such abstract functions. Further, these notions of equivalence tend to be too liberal in that schemas are often considered equivalent when a practitioner would consider them to be different. As a result, practical integration methodologies have not utilized this theoretical foundation and most of them have relied on ad-hoc approaches. We present results that seek to bridge this gap. First, we consider the problem of deciding information capacity equivalence and dominance of schemas that occur in practice, i.e., those that can express inheritance and simple integrity constraints. We show that this problem is undecidable. This undecidab...

. Changes in market and production profiles require a more flexible concept of manufacturing. Computer Integrated Manufacturing (CIM) describes an integrative concept for joining business and manufacturing islands. In this context database technology is the key technology for implementing the CIM philosophy. However, CIM applications are more complex and thus, more demanding than traditional database applications like business and administrative applications. In this chapter we systematically analyze the database requirements for CIM applications including business and manufacturing tasks. Special emphasis is given on integration requirements due to the distributed, partly isolated nature of CIM applications developed over the years. An illustrative sampling of current efforts in the database community to meet the challenge of nonstandard applications like CIM concludes this chapter. Categories and Subject Descriptors: H.2.8 [Database Management] Database Applications; H.2...