Interface Concepts provides a good summary of conceptual design concepts:
The process of conceptual design involves a set of steps for translating requirements into a user interface design. The process begins by getting at the core of an application--the central concept--and proceeds by organizing the functionality from the users' point of view. Along the way, a deeper understanding of users and their requirements is developed. The result is an outline or model of the user interface that may be further developed during the detailed user interface design phase.
The conceptual design process involves the following steps:
- Define a central concept.
A concise statement of what the application is and what it is not. It clearly defines the boundaries of the application and characterizes the overall users' view of the application.
- Describe user roles and their requirements.
A list of who the target users are, what their roles are in their use of the application, and what is important to them--such as getting work done quickly, being in charge, and feeling successful.
- Define and prioritize measurable objectives and constraints.
Objectives for the user interface are the designers' intentions such as:
- to reduce repetitive tasks,
- to have users feel in control, and
- to provide satisfactory feedback on results.
Operational definitions specify how the design will be measured against the objectives, for example, in usability testing. Constraints define the design space within which the objectives may be achieved, such as display resolution, response time, and availability of a pointing device.
- Design the user's object model.
A table of all objects the user needs along with their attributes, actions, contents, and relationships among objects.
- Design the user's task model.
A list of all tasks the user needs to perform with procedures on how to perform each task using the application.
- Synthesize a user interface model.
The user interface model organizes the functionality according to the object and task models. This is a rough outline of the user interface that guides the detailed design phase.
- Evaluate results against the objectives.
Various evaluation methods, such as heuristic evaluation and usability testing are selected to measure how well the objectives have been achieved..
Source: Interface Concepts