Describing the UserOverview of User Modeling

The purpose of user modeling is to paint a picture of a user's world. In the case of user-centered design work, this picture must be detailed enough to create usable systems but simple enough that the cost of creating this picture of the world is not prohibitive. The focus of this model of the world is a description of each significant population of users and, for each population, the significant tasks performed by the population and the concepts (referents) used in the course of performing those tasks.

Modeling user populations is discussed in: Users and Their Organizations.

Each user's world is filled with referents. Referents are those things, tangible and intangible, that are the object of a user's activities. The ETP architecture refers to each kind of referent as an Entity. Modeling entities is discussed in The User's Domain.

Next, there are the activities that manipulate these entities. The ETP architecture refers to each type of activity as a Task. Modeling tasks is discussed in User Tasks.

Finally, to understand how best to support the users' tasks, we also describe the representation of the entities needed to help complete a task. This representation is called a Presenter. Modeling presentation is discussed in User Interface.

The significant parts of the user's world are thus divided into Entities, Tasks, and Presenters. This three-way division is the basis of the ETP UI architecture and is illustrated in the following figure.

UML class diagram describing the basic components of a user model: actors (users), entities (referents), tasks, and presenters. These concepts are further described by the ETP architecture.

This UML class diagram also illustrates the principal relationships between these four elements. Actors perform tasks. Tasks have knowledge of or are defined, in part, by the entities which they manipulate. Presenters each support a task by facilitating completion of that task. Presenters do this by showing, in an appropriately structured presentation, an entity or some aspect of an entity.

These concepts and their relationships form the core of any user model.