Four Patterns from the wu Pattern Language: a Pattern Language for Web Usability

patterns represent the codification of principles, often derived from subjects such as cognitive psychology or ergonomics. Unlike concrete patterns, they usually have no initial context. An example of an abstract pattern that derives more from common sense than from scientific endeavour is KISS (38). This pattern encodes the principles of simplicity that Jakob Nielsen has argued for so cogently and passionately over the last few years. There can be no context for such a principle; its just always a useful one and informs the way downstream patterns are applied and interpreted. Abstract, concrete and terminal patterns Concrete patterns are patterns in the usual sense and we discuss their structure in detail below. Finally, some patterns are terminal with the wu language. Patterns being terminal does not mean that design thinking stops with them – merely that the language considers the further design issues as beyond its scope or ambitions. For example, we do not consider patterns that do not concern usability specifically. Such patterns evidently exist: detailed patterns for attracting more visitors to your site or upping advertising revenue for instance. The other cases where the language terminates abruptly usually concern areas of some complexity that, in our opinion are deserving of pattern language in their own right. The examples that spring to mind are designing sites for the physically or mentally handicapped and making the site attractive to look at – the sort of thing that you need a good graphic designer for. Clearly, both areas concern usability but we quail at including the complexities of these topics. First, it would make the language large and large things are generally unwieldy and hard to use. Secondly, we do not feel especially competent in these areas. We would encourage those others who are competent to set about building languages for these important topics. The scope and boundaries of the language Personalization is a borderline case. It is clear that personalization influences usability but it is not clear exactly how. One can state that when personalization works usability should be enhanced but it is possible that badly thought out personalization could make a site less usable for some of its users. For example, we recall being irritated by Amazon’s ‘recommendations’ on several occasions – not a very serious defect admittedly but bad nevertheless. We decided not to include it within wu because we felt that not enough was known about it at this time to justify its ossification in a pattern. So, while it is an important and interesting topic it remains out of scope at present. Work on a pattern language for personalization has been started by Koch and Rossi (2002). Another case is borderline. Veen (2001) commends the use of cascading style sheets (CSS) to help separate presentation from content, thus assisting with maintenance and usability. CSS is a standard for describing how content should appear on HTML pages by adding tags and instructions to the browser as to how these tags should be rendered. One can control things like founts and margins very effectively in this way – though not as well as with the projected XML tags of Tim Berners-Lee’s semantic web we suspect. In the end we decided that CSS was a technique just outside of the scope of wu, if we had included it we would have called it, following Veen, GETTING STYLISH. Abstract patterns are never terminal of course. References to patterns are always set in bold, sans serif small capitals. On the wu web site these become hyperlinks to the patterns concerned. Patterns always start on a new page. Rules are made to be broken. The patterns in the chapter may be regarded as rules for successful design but it is better to think of them as providing suggestions, guidance and checklists of things not to forget to think about. If you do find yourself treating the patterns as rules then pause. Always consider the likely effects of breaking the rules and ensure that you understand the rules that you are going to break and the justification for doing so. Each pattern is presented using the same layout, semantic structure and typographical conventions. These are very closely based on the structure pioneered by Alexander et al. (1977). The pattern number and name are presented first, followed, optionally, by a list of alternative names. The latter, if present, are labelled AKA (also known as) in the margin. Next comes what many people call a sensitizing image: a picture or diagram concerning, supporting or illustrating the pattern. In many, but by no means all, cases this is a screen shot taken from a web site. The structure of a pattern After the sensitizing image we present the context in which one would normally encounter the pattern. With the exception of some abstract patterns, this section usually gives the names of patterns that one has already used or considered. This is separated from the body of the pattern by three tildes, thus: