The graphical user interface for an EC/EB system is developed in two steps. First, a user interface prototype is designed. This prototype is also used by marketing to support accompanying advertising measures.

The prototype development begins with writing a storybook that is based on the use cases. This storybook is then used to define a style guide and, in a second step, to realize and implement the user interface for the EC/EB system. For the IPSI electronic commerce portal, this was done for multiple access channels (WWW, WAP).

Besides the portal's specific functionality in the B2E application domain, its content is also a significant element. The content comprises all the information that the electronic commerce portal provides, as well as its presentation within the user interface. Content often has multi-media characteristics, i.e. it comprises textual information, graphic figures, moving and still pictures and audio information. Consequently, a content manager who is responsible for the multi-media information is an important role in the software development process. This is a new role that can comprise other roles, such as the media author who collects information and reworks it for a consistent presentation; the media designer who is responsible for the audio-visual design of the user interface; and the media producer who researches available media, creates images, graphics, animations, audio and video sequences, and clarifies copyright issues. Media editors are responsible for quality assurance in the multi-media content part of the application.

In addition to the role of content manager with its many tasks and responsibilities, the role of ergonomics advisor has to be taken by a team member. The ergonomics advisor's task is to ensure that the user interface of the electronic commerce portal is design ergonomically, i.e.

• it is suited to the tasks the user has to accomplish
• it guides the user by being self-explanatory and gives additional help on request
• it lets the user decide how to use the system without forcing them to follow a predefined set of procedures
• it describes errors the user makes and allows their correction with limited effort
• it can be adapted to the user's level of experience

User manuals can be differentiated into tutorials and references. For the creation of the user manuals, a styleguide is used that describes what the complete user documentation will look like. For the creation of a tutorial, the storybook that was already used for the user interface prototype is used again.

Figure 5. User interface design subprocess model.

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