Cohesion of Object Histories

In an earlier paper, one of the authors introduced a record-based, algebraically-oriented, event-driven model for describing historical data for objects (here called “object histories”). The major construct in the model is a computation-tuple sequence scheme (CSS) which specifies the set of all possible “valid” object histories for the same type of object. The current paper considers the problem of combining the global information residing in a number of object histories in a distributed system. A suggested solution is in the form of an operation called “cohesion”, which is the analogue for object histories of join for relational databases. The basic question considered in this paper is the following: Given two sets I1 and l2 of object histories described by CSS T1 and T2, does there exist a CSS which describes the cohesion of l1 and l2? The answer is shown to be yes by constructing a specific CSS (called the “cohesion” of T1 and T2) from T1 and T2. The cohesion operation also turns out to be a useful tool for establishing some subsidiary results.