Software metrics for non-textual programming languages

Most software metrics and cost model tools are based upon the Line of Source Code unit measure of software. Lines of code have no equivalent in a diagrammatic-graphical programming paradigm. Programs developed in National Instrument's "G" or LabVIEW(R) development environment are represented as a hierarchy of Virtual Instruments. A virtual instrument (VI) consists of a virtual front panel window and a programmatic diagram window. The front panel provides the program interface and the diagram provides the implementation. This paper describes several features of the front panel and the diagram that influence program storage size, execution speed, memory requirements and maintainability. The VI Hierarchy is described along with the relationship of the hierarchy width and depth to code reuse and program complexity. The VI Profiler and LabVIEW(R) add-in products such as the "Professional G Developers Tool Kit" are examined, as is an adaptation of the McCabe Cyclomatic Complexity Metric.