Using persistence to support incremental system construction

This paper describes the use of a persistent store to support incremental system construction. A single example is elaborated throughout the paper to introduce elements of the incremental construction mechanism. The essence of the technique is to permit assignment of executable program fragments to typed locations in order to change the behaviour of a program under construction. The technique described in this paper relies upon the existence of three features: a persistent store, updatable locations and first class executable values. The examples in this paper use the persistent programming language Napier88, but any language with these features could be used to construct such a system.