Measuring program structure with inter-module metrics

A good structure is an important quality aspect of a program. Well-structured, modular programs are less costly to maintain than unstructured monolithic ones. Quantitatively assessing structure and modularity of programs can be useful to help ensure that a program is well-structured by indicating a potential need for restructuring of poorly structured code. However, previous structure metrics do not sufficiently account for the modular features used in modern, object-oriented programming languages. We propose four novel measures to assess the modular structure of a software project. Our measures are based on the principle of vocabulary hiding and measure a form of cohesion. A metrics prototype tool has been implemented for the Modula-3 programming language. Informal tests suggest that they are indeed useful to assess the quality of the program structure