Software Design 2e - DIM

system. The results of this study undoubtedly provide illustrations of several of thecognitive dimensions!)The cognitive dimensions offer some interesting ideas to employ in thinking aboutdesign quality and what it can mean for software. We will be returning later to makefurther use of some of the ideas that they embody. However, having examined some ofthe quality factors that designers would like to be able to assess in making their decisions,we now go on to consider what measures of quality we actually have availableto us at the design stage. We can then consider how well these are able to provide helpwith assessing the extent to which a design meets the factors that have been describedabove.4.3 Quality attributes of the design productNow that a number of ideas about design quality concepts have been examined, it isclear that the two principal problems that they present for measurement are:nnto identify a set of design attributes that are related to these properties;to find ways of extracting information about these attributes from the availableforms of design document.75Quality attributes of the design productIn the first part of this section some of the attributes and criteria that are widely usedfor design assessment are described, and this is followed by a brief discussion of one ofthe ways in which these might be extracted.4.3.1 Some design attributesSimplicityCharacteristic of almost all good designs, in whatever sphere of activity they areproduced, is a basic simplicity. A good design meets its objectives and has no additionalembellishments that detract from its main purpose. (Perhaps this is why so manydual-purpose artifacts fail to achieve either of their objectives clearly and well. Oneexample that comes to mind is a rucksack that expanded to become a tent, but wasunsuccessful because it was much more convenient to have a good rucksack and agood tent as separate items. Most of us can probably think of similar examples of misplacedingenuity.)The often-quoted saying ‘a solution should be as simple as possible, but nosimpler’, which is usually attributed to Albert Einstein, is more profound than it mightseem at first. This is the opposite of the argument against unnecessary embellishment:it argues against attempting to oversimplify, since the result will be a product that willnot be able to do its job. One important aid to achieving simplification is abstraction,but it is necessary to use an abstraction that preserves the relevant attributes if it is tobe of any help in solving the problem.While simplicity cannot easily be assessed, one can at least seek measures for itsconverse characteristic of complexity. A number of these, which measure differentforms of complexity, have been developed for use with software, including: