In conventional object systems, the functional behavior of an object follows patterns that have been ingrained into it upon its creation. This makes it impossible, or at best highly cumbersome, to permit an object to participate -successively or concurrently -in a number of object societies of largely divergent goals and tasks and, hence, with environments of divergent and changing message needs. What seems desirable, instead, is a variation of the traditional object model in which an object itself becomes aware of the situation it is in or may move to, then adapt its currently desirable behavior accordingly. Awareness means that the environment must become observable to the object, which in turns requires some sharing of state information among objects. Adaptation entails that an object must be capable of associating with different (though perhaps overlapping) sets of operations, or adjust the effects of its operations.
The paper, by taking its cues from role models and relationship models, demonstrates that both objectives can be met by a slight modification of the object paradigm that splits an object into two parts, a kernel called crystal which carries the identity of the object and, hence, is the addressee of messages, and constructs called contexts, which a crystal may variably connect to, across which the internal and external states of the object and the operators are spread, and which respond to the messages while the crystal coordinates these responses. A notion of situation forms the centerpiece of typing. The paper motivates the choice of model, defines and illustrates the basic constructs of the model, describes how a particular behavior can be obtained and adapted, considers how typing can be achieved under the changing conditions, and finally reports on first experiences in design, implementation and application.