Model-Based Design for Embedded Systems- P33: This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. | 286 Model-Based Design for Embedded Systems waiting for blocking other processes. A process may atomically propose multiple events this represents nondeterminism in the system. After all processes in the base model are blocked the design shifts to the second phase. The execution of processes between blocking points is beyond the control of the framework. 2. Quantity annotation. In the second phase each of the proposed events is annotated with various quantities of interest. For instance a proposed event may be annotated with local and global time tags. New events may not be proposed during this phase of execution. In this way events and the methods they correspond to can be associated with cost. 3. Constraint solving. In this phase a subset of the proposed events is enabled and permitted to execute while the remaining events remain suspended. Events are enabled according to schedulers and constraint solvers. These enabled events then become inactive again while simultaneously allowing their associated processes to resume to the running state. At most one event per process is permitted to execute. Once again new events may not be proposed during this stage. Constraint solving may be based on the resolution of declarative constraints or on the imperative code. A collection of three completed phases is referred to as a round. After the constraint solving phase the states of some processes are switched to running while some others might still be suspended. The execution will then shift to the first phase and start a new round. Those processes that are in the running state will resume their executions. The iterations of these three phases will end when all processes finish their executions. Figure illustrates the process states event states and the three phases in the execution semantics. Self loops on the inactive and annotated states illustrate that multiple rounds may pass without an update to a particular event s state. Table illustrates the relationships
