The implementation of a Chronicle collection class in Smalltalk/DB

Abstract

In this paper, we present the implementation of a compact temporal object model based on time sequences as a general purpose collection class, called the Chronic le, in the Smalltalk/DB language. This provides an object database with the potential to express temporality and so creates a semantically rich environment for implementing applications that model temporally variable objects. We describe the concepts of the Chronicle class and give a detailed description of its components. This implementation supports the time-stamping of objects with transaction times and valid times, and does not depend on multiple inheritance as a mechanism for conferring temporality. Our implementation creates no additional barriers to schema evolution and instance migration, and storage performance is enhanced by the sharing of components that~specify temporal semantics. However, because the class--es of objects stored in a Chronicle are not known in advance, a comprehensive set of query methods cannot be generated and many queries must be created as low level expressions.