The interface components and relationships intended to be seen by users and intended to become part of each user's conceptual model are described in the designer's model. This model represents the designer's intent in terms of components users will see and how they will use the components to accomplish their tasks.
The designer's model identifies objects, how those objects are represented to users, and how users interact with those objects. User oriented objects are defined in terms of properties, behaviors, and relationships with other objects. Differences in properties and behaviors are the basis for class distinctions, such as the distinctions between folders and documents. Relationships between objects affect how they are used in accomplishing users' tasks. For example, users can use folders to contain and organize memos, reports, charts, tables, and many other classes of objects. Users can discard an object by dragging and dropping the object's icon on a wastebasket icon, and users can print an object by dropping the object's icon on a printer icon. These actions are logical in that they maintain real-world relationships between objects.
Traditionally, the "user interface" of a product has been considered to be the "look and feel" aspects of the product. More recently, the emphasis has been shifting to the objects needed by the user to accomplish their tasks. This is the basis of an object-oriented user interface, or OOUI. A more complete picture of the designer's model is represented in the Designer's Model Iceberg, in which the look and feel aspects of the interface constitute the "tip of the iceberg", and the most important aspects are encapsulated in the object model. An object model describes objects, properties, behaviors, and relationships intended to be seen and used by users of the interface. The object model is the main component of the designer's model in an object-oriented user interface. The "look and feel" aspects play a supporting role.
By relying on a few basic classes and relationships, with well-defined distinctions based on user task needs, the designer's model should be easy for users to learn and understand. Users should quickly develop conceptual models that closely match the designer's model.
The Workplace OOUI Model is an example of a designer's model. This model defines objects that are common to many types of applications. Product designers add objects that are needed by specific products. This is typically done by extending existing objects (creating subclasses) or by defining entirely new types of objects (creating new classes). Definition of the designer's model is crucial to developing products that are easy to learn and understand. Its definition should comprise the first series of steps during product design.
If the designer's model closely matches a user's conceptual model, the user should learn quickly and apply knowledge correctly in new situations. In other words, the user will feel the interface is intuitive. Designers can help users to develop a closely matching conceptual model by creating a clear and concise designer's model. A designer's model is clear and concise when it has made a minimum number of distinctions among objects, the distinctions are clear and useful to users, and they are consistently conveyed throughout the interface.
For the designer's model to be consistent with the user's conceptual model, the designer must know the users, their tasks, and their expectations. If designers do not understand their users, the interface will not behave as users will expect it to. If the system does not behave as users expect it to, their conceptual models will be different from the designer's model and misunderstandings will occur. Users can lose confidence in the reliability of their conceptual model, and thus in the system itself, when these misunderstandings occur. If users form an incorrect conclusion or a superstition to explain an inconsistency, they may try to apply it elsewhere in the system. This can lead to further misunderstandings and distrust of the system.
A misunderstanding can be caused by inconsistency in an object's behavior resulting from a particular action. For example, if a user learns that double-clicking the mouse button on an object opens a window, and elsewhere in the interface the same action discards an object instead, the user will quickly learn to distrust the system.
In summary, the designer's model is the model of objects, properties, behaviors, and relationships that the designer intends the user to understand. The designer's goal is that each user's conceptual model exactly matches the designer's model. Users who perceive the interface at this level have a precise understanding of the interface and can take full advantage of the capabilities intended by the design.