Software Engineering Institute

Durra is a language designed to support the construction of distributed applications using concurrent, coarse-grain tasks running on networks of heterogeneous processors. An application written in Durra describes the tasks to be instantiated and executed as concurrent processes, the types of data to be exchanged by the processes, and the intermediate queues required to store the data as they move from producer to consumer processes.

The tasks and types available to an application developer are described by a collection of Durra task descriptions and type declarations stored in a library. One of the components of a task description is a specification of the external timing behavior of the task. It describes the sequence of input and output port operations and the amount of processing time spent between port operations.

This report describes MasterTask, a program that can emulate any task in an application by interpreting the timing expression describing the behavior of the task and performing the input and output port operations in the proper sequence and at the proper time.

MasterTask is useful to both application developers and task developers. Application developers can build early prototypes of an application by using MasterTask as a substitute for task implementations that have yet to be written. Task developers can experiment with and evaluate proposed changes in task behavior or performance by rewriting and reinterpreting the corresponding timing expression.