Measuring reusability of DEVS simulation models

Abstract

Reuse technology in simulation modeling is one of the important technologies to build simulation models with great productivity and quality, in that developing simulation models from scratch requires considerable costs and efforts to design, implement and test the models. It is known that there is a powerful reuse framework in the simulation modeling with DEVS(Discrete Event System Specification) formalism and object-oriented environment DEVSIM++. The DEVS formalism provides specification of discrete event models in hierarchical, modular form. The hierarchical, modular specification offers a basis for reusable model base, which supports powerful reuse in simulation modeling. The DEVSIM++ implements the DEVS formalism in an object-oriented programming environment, C++. In simulation modeling with DEVS and DEVSIM++, reuse can be occurred in two ways. One is compositional reuse based on closure under coupling principle from DEVS formalism, and the other is modification reuse through inheritance supported by object-oriented paradigm. Measuring such reusability has been required to monitor and improve the process of simulation modeling. In this thesis, the measures of model reuse are derived and empirical results are presented by measuring DEVSIM++ codes developed for R&D projects and coursework term projects in KAIST. Two abstractions are suggested to derive measures for the reusability in developing simulation models in DEVSIM++. One is composition tree which is the structure of a hierarchical model and captures the compositional reusability. The other is class inheritance hierarchy graph which captures the modification reusability. The tools are developed to measure the reusability automatically, and the guidelines are suggested to increase model reuse in developing simulation models.