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4.3.1. Task Model Dialogue Design and Detail Design
The primary means of communicating the users conceptual model and supporting the tasks identified in the Refinement and Analysis Stage is through dialogue design. Dialogue design includes the contents and ordering of windows and dialogue boxes in an application that allows a user to complete a given task. The flow of the dialogue in the interface should be designed to follow the flow of the tasks identified in the Refinement and Analysis Stage. The dialogue should be structured to maintain consistency in the behavior of objects: they should not arbitrarily appear, disappear, or be changed.
Although ideally dialogue design for each task should precede detail design (window layout and type of controls), in reality these are often done concurrently. This is particularly true for small screen devices, such as Orbitor, where the limited screen real estate will often impact the ideal dialogue flow.
Dialogue and detail design for relatively simple graphical user interfaces can be largely completed through the use of the prototyping techniques described earlier. Larger and more complex interfaces (e.g., a multimodal user interface) would require the use of more sophisticated tools, such as flow charts, state transition diagrams, or an on-line dialogue design and management tool.
With user interfaces for standard operating systems (Macintosh, Windows, etc.) the designer can refer to style guides to help with the detailed design. With new-generation products such as Orbitor, the detail design comprises a significant proportion of the new look and feel of the product. It also constitutes a major amount of the design effort. For this type of project, graphic and visual interaction designers should be part of the design team from the Exploratory Stage onward.
4.3.2. Metaphors
A metaphor is used to map an object or action in an interface to something else the user might already understand. Metaphors should communicate the users conceptual model of the new interface by expressing it in terms of other objects or actions with which the user is already be familiar.
Metaphors should be selected for their appropriateness to the target market and they should also be matched to the experiences and capabilities of typical users. All of the metaphors used in an interface should also be unified with respect to each other (i.e., they should follow a common theme). For new generation products, the goal is to build upon and extend users experience with existing products.
Metaphors, particularly visual metaphors (e.g., graphical icons) are useful for improving the initial discoverability of an interface for new users. While the user interface concept being conveyed may be either an object or an action, it is easier to communicate a metaphor that is related to real-world physical objects. The real value of graphical metaphors is not that the user intuitively understands it from prior experience with the mechanical real-world equivalent, but that it is both simple to discover and memorable. Well-designed graphical icons can make use of recognition memory.
One of the problems with overly-explicit metaphors is that they become constrained by the properties of the physical real world object. Thus, a major functional gap evolves between the capabilities of the application and the more limited capabilities of real world objects. Some designers have shown that users do not perceive explicit graphic metaphors and that they will perform the same with or without them. (Spool, 1996).
A well-designed metaphor should strongly encourage exploration, discovery, and learning without penalty (e.g., including the ability to undo mistakes and try again). For products which will be used on an ongoing basis, the interface should be designed to facilitate the transformation of new users into expert users (who do not require explicit graphical metaphors).
Using a brainstorming technique (see Michalko, 1991) with a team of designers is a fast way of developing a range of metaphors. For new generation products, antecedent products (studied in the Refinement and Analysis Stage) can be a good source of metaphors. As computers become ubiquitous, established ideas in the desktop computing environment can also be a source of metaphors.
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