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Show CHAPTER 2 DEFINITION 2.1 Introduction A central question of introspection is what constitutes the computational behavior of a process. We want to find a way to capture the complete description of this behavior and express it in a form that is amenable to analysis by another process. The calculus of delta sets was developed to provide a notation for basic terms used in the thesis. Using the calculus, the computational behavior of the process can be specified in exact terms. This provides the foundation for a definition of introspection. A process is ultimately executed by an interpreter which can be in hardware or in software. In an introspective computer, a regular interpreter must be supplemented with additional features to facilitate the communication between the executor and the director. An introspective computer offers capabilities not available in regular computer systems. Two examples are illustrated, the detection of an infinite loop and the resolution of a deadlock. The summary at the end of the chapter is sufficient to follow subsequent chapters. 2.2 Formal Model A formal model of introspection must be able to express the computational behavior of a process in a form that enables efficient monitoring by another process. A way to monitor the process is to stop the process after every step and to examine its state. An alternative is to monitor only steps and their effects on the process state. These two methods are orthogonal. Both are useful in monitoring. We want our model to capture these two methods of monitoring in a uniform way. |
