What is quality? Quality is not an absolute intrinsic measure neither for tangible goods nor for intangible ones such as object-oriented design. Quality can only be measured relatively to a particular point of reference and depends on the assessor's view of the objects to measure as well as the reference point. The view defines the various aspects to be considered regarding measuring quality such as reliability, performance, or security.
These aspects span a multi-dimensional space in which no universal linear ordering relationship can be defined regarding quality. We refer to the view and its related multi-dimensional space as viewpoint. If we change the viewpoint then that what we consider good quality changes as well; if we change the point of reference then the degree of the quality changes.
Kai-Uwe Mätzel and Dirk Riehle. "Object-Oriented Design Quality." Position Paper for OOPSLA '97 Workshop 12 on Object-Oriented Design Quality.
The paper is available as a PDF file.