People often ask me either to design a "usable" web site or to review one and make comments and recommendations on its usability. My first step is to generate as many realistic scenarios of use as we can construct or envision. By generating such scenarios, a designer engages in a process of specifying interface objects and actions for given contexts. This is done from the perspective of the user. Identifying relevant design objects for given contexts, as well as specifying user actions from a human-centered perspective is at the core of what I call the "userview" process.

Specifying context is important to the web design process because context helps us first understand how objects within a universe of discourse relate to each other to form a coherent whole. Also, context provides us with a framework in which to relate objects to their surrounding environments. Focus on the user early in the design process produces user-centered web design. Let us consider more carefully the three design concepts of scenario, context, and userview.

Scenarios

Creating successful scenarios requires us to answer the following four questions:

1. Where and under what conditions will the web site be used?
2. For what purpose will the site be used?
3. Who will use the site (the target audience)?
4. How will the site be used?

There may be many answers to each question. The permutations of the different combined answers constitute all the possible scenarios. Some combinations are naturally more realistic than others. A good designer is able to weed out the unsuitable ones....

Context

Scenario development allows us to consider the objects and actions needed for design. Context is the relationship of these objects and actions to each other and to their environments. "The weaving together of parts into a coherent whole" describes the object's relationship to other objects. This is an important sense of context in web design because it addresses the issue of how information should be organized. For example, it determines the placement on a web page of a label relative to a field or a header to text, that is, the spatial placement of objects that are semantically close (similar in meaning) to each other.

A second essential way in which to define the context of an object for web site design is to view context as "that which surrounds the object." In this sense, context can be either cognitive or physical. For example, cognitively, the context of a word is a function of the sentence containing the word. An example of physical context is a book on a shelf of books in the library. The other books and the library are both contexts in that they surround the target book. As we will see in chapter 3, the union of physical and cognitive contexts is quite important to web design. In web site design we must also consider an object's relationships to many environmental levels, which can be represented as ever-larger concentric circles....

A cognitive example of context as "that which surrounds" an object is the selection of words to convey meaning. Here we need to consider the relationship of the word we select to the sentence, the paragraph, the document, the topic, the field of specialization, and the reading audience. Each of these environments, starting with the sentence, is a successively larger context in which to consider the choice of words to use....

Using a contextual strategy to design web sites requires us to consider five levels of design context. These are:

• the extrinsic environment context
• the user context
• the genre context
• the site context
• the page context.

Designing contextually for each level means considering not only how objects relate to each other at any given level, but also how the contexts relate to each other.

Design decisions made in the larger (contexts)supersede those made in the smaller ones. This order of superseding is fundamental to the strategy of contextual design. The extrinsic design context refers to the actual physical and cognitive spaces in which users visit a web site. The user context refers to the audience requirements, such as web user cultural constraints or a user's physical limitations. The genre context specifies the type of site, such as news media, tourism or shopping. The site context refers to the user, or human, interface relating to characteristics such as site navigation and organization. The page context addresses design constraints inherent in a single page.

Design decisions made at higher levels supersede decisions made at any lower level. Let us say we are designing a tourism site. In the tourism genre, the proportion of graphics to text is high on a given page. If we are designing for a culture where the practice is to convey information mainly textually, then this user constraint of textual pages would supersede the tourism genre characteristic of a high proportion of graphics.

Using another museum scenario example, we start by considering design decisions relative to the location where the web site will be used. If we determine that the site is intended to be used mostly in KÐ12 classrooms, then the extrinsic context suggests that the visitors to the site will be groups of children rather than individuals. This "group" characteristic carries with it a certain set of constraints that will impact how to design interaction and navigation at the site level. Under such constraints, the designer may have to consider using voice, video, audio, and possibly a remote control. The "group usage" characteristic will also require that pages be designed with relatively large objects that can be seen from a group distance. The museum genre context will call for a site with color graphics and possibly spatial navigation, even though for the sake of simplicity we recommend that the designer avoid 3-D elements for navigation at the site level and avoid graphics at the page level. Here the design decision at the genre level supersedes those at the site and page levels.