They need only learn the distinguishing features of the portfolio to take advantage of its benefits. Object classes and subclasses seen by users should be derived directly from analysis of users' tasks and understanding users' goals, motivations, and current techniques. In this way objects presented through the computer interface will be more easily recognized and their rules more readily understood. An object's composition contributes to its class membership and therefore to establishing its properties and behaviors. Many kinds of objects are also containers of other objects.
Users interact with objects through views.
Typical user tasks involve working with a variety of object properties, using various object behaviors, and working with several objects at once. In practice it's difficult to support all necessary tasks using a single view of an object. Objects typically must provide multiple views, each specialized for a specific set of tasks. Views span all presentation forms, including nonvisual forms such as audio. The basis of OVID is a methodical analysis and design approach to identifying objects, defining views for sets of desired tasks, and specifying the interaction techniques used within each view to accomplish tasks.