Measuring OO systems: a critical analysis of the MOOD metrics

In parallel with the rise to prominence of the OO paradigm has come the acceptance that conventional software metrics are not adequate to measure object oriented systems. This has inspired a number of software practitioners and academics to develop new metrics that are suited to the OO paradigm. Arguably, the most thorough treatment of the subject is that of the MOOD team, under the leadership of Abreau. The MOOD metrics have been subjected to much empirical evaluation, with claims made regarding the usefulness of the metrics to assess external attributes such as quality and maintainability. We evaluate the MOOD metrics on a theoretical level and show that any empirical validation is premature, due to the majority of the MOOD metrics being fundamentally flawed. The metrics either fail to meet the MOOD team's own criteria or are founded on an imprecise, and in certain cases inaccurate, view of the OO paradigm. We propose our own solutions to some of these anomalies and clarify some important aspects of OO design, in particular those aspects that may cause difficulties when attempting to define accurate and meaningful metrics. The suggestions we make are not limited to the MOOD metrics but are intended to have a wider applicability in the field of OO metrics.