This paper describes an active semantic database model that copes with
the issues of automatic enforcement of dependencies among various por
tions of fragmented (possibly heterogenous) database. Dependencies are
defined as computational invariants, which are database schema primit
ives. The invariants are defined independently of implementation issue
s such as distribution of the database and physical tool of implementa
tion. Dependency definitions are translated into PATH structures (impl
ementation-independent knowledge representation entities) that accumul
ate syntactic and semantic knowledge about the dependencies. After com
pletion of the physical design, the PATH structures are refined using
DMP (distributed matching protocol), which determines the contents of
interdatabase transactions to maintain the consistency of a distribute
d system relative to the defined-sequence of invariants. The paper dis
cusses these concepts and relevant implementation issues and illustrat
es the concepts using a complete case study.