Automated module composition

Abstract

We define an abstract problem of module composition (MC). In MC, modules are seen as black boxes with input and output ports. The objective is, given a set of available modules, to instantiate some of them (one or more times) and connect their ports, in order to obtain a target module. A general compatibility relation defines which ports can be connected to each other. Constraints are imposed on the number of instances of each module and the number of copies of each port. A linear objective function can be given to minimize the total cost of module instances and port copies. The MC problem is motivated by the need to automate the composition of legacy modules used in the development of software embedded in cars. Due to the large number of modules, composition "by hand" is tedious and error-prone, and its automation would lead to significant cost reduction. We show that the MC problem is NP-complete, by formulating an equivalent integer optimization problem. We also identify a number of special cases where the MC problem can be solved in polynomial time. Finally, we suggest techniques that can be used for the general cases. © Springer-Verlag Berlin Heidelberg 2003.