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2. OVERVIEW OF THE DELTA METHOD

The Delta Method is developed as a framework for usability activities within software development projects. The method assembles existing usability tools and practices into a usability process (see Figure 7.1) that supplements the early phases of traditional system development. It is our experience that it is crucial to perform the usability activities at the early phases of a project and as an integrated part of the system to have an impact on the system design.

In large development projects, the requirements specification often represents the “absolute truth”. If usability engineering is applied too late, i.e., after the requirements have been defined, there is an apparent risk that the usability requirements will be considered as “unfeasible proposals for late changes”. It then becomes a matter of either approving the usability of a finished product or to “put lipstick on the corpse”. The user interface might be aesthetically pleasing, but the system will not offer the appropriate services.

The Delta Method focuses on finding and eliciting the requirements of the future users. This is accomplished through interviews, observations in the workplace, and studies of users’ interaction with prototypes. The tight integration of the method into the existing system development process raises the usability requirements to the same level as the technical and functional requirements. They are no longer optional or add-ons to the requirement specification. The Delta method is summarized in following inset.

The method is designed to be used by system developers and technical communicators with limited formal knowledge of usability work. Trained usability engineers and human factors specialists are still very scarce in Swedish software development companies, a situation that has led us to adopt on-the-job training. We supply a method that produces good results even if the work is performed by workers not trained as usability specialists. Selected system developers and technical communicators take part in basic usability training and then receive support from an experienced usability engineer during their first projects.

System definition
Define the scope of the proposed system and identify preliminary user categories and system services.
User profiling
Create detailed user profiles for each relevant user category.
Task analysis
Identify and record all relevant user activities of the current work practice.
Design preparations
Restructure and reinvent the current work tasks.
Usability requirements
Define usability requirements that the prototype and the finished system must meet.
Conceptual design
Create a conceptual model of the system services that support all future work tasks.
Prototyping
Design prototypes, using paper or computer, that reflect the conceptual model.
Usability tests
Observe representative users testing the prototype. Evaluate how well the system meets the requirements and redesign the prototype if necessary.
UI implementation
Support the system developers with user interface development skills during the implementation of the applications.

Other sources for information regarding the Delta Method are the Delta Method Handbook (Ericsson Infocom, 1994) and The Delta Method — A Way to Introduce Usability (Rantzer, 1996).

2.1. WHAT IS SPECIAL ABOUT DELTA?

The Delta method is a tool for improving the communication, both within the development team and between the team and the users. It is a way of performing usability engineering in which the system designers, technical communicators, and usability engineers are supported in carrying out the user and task analyses and in designing the user interface.

The system designer typically works with the definition of the system in the early phases of the project. He or she has the main responsibility for the design of the system’s internal functions and the detailed design of the system services for the user interface. The systems designer usually has a background in (object-oriented) system modeling and as such is a key actor during the conceptual design.

The technical communicator, or technical writer, has the main responsibility for the enabling information, i.e., on-line help, user guides, etc. He or she also has to ensure that the user interface and the tasks performed by the system are designed in a way that is accessible to the user. The technical communicator plays an important role, deciding what information should be included in the system, and finding an appropriate structure for the user interface, system services, and enabling information. The technical communicator should also (together with the usability engineer) act as a link between the designers and the users since he or she often has both training and experience in how to explain complicated technical issues to inexperienced users.


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