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Durra is a language designed to support the development of distributed programming applications consisting of concurrent, large-grained processes devoted to specific pieces of the application. During execution time the application processes run on possibly separate processors, and communicate with each other by sending messages of different types across communication links. The application developer is responsible for prescribing a way to manage all of these resources, called a task-level application description. It describes the processes to be executed, the assignments of processes to processors, and the communication channels required to transmit messages data between processes. Durra is a task-level description language, a notation in which to write these application descriptions. This document is a revised version of the original reference manual. It describes the syntax and semantics of the language and incorporates all the language changes introduced as a result of our experiences writing application descriptions in Durra. A companion document, Durra: A Task-Level Description Language User's Manual, describes how to use the compiler and support tools.

Durra is a language and support environment for the specification and execution of distributed ADA applications. The Durra programmer specifies the distribution of application components by assigning them to virtual nodes called clusters. For each cluster named in an application description, the Durra compiler generates an ADA package body with a standardized format. Within the confines of the format, the content of the package body varies according to the requirements placed upon the cluster by the Durra application description. The cluster-specific package body is compiled and linked with a fixed set of ADA compilation units, common to all clusters, to form a multitasking ADA program. The intended audience for this document is Durra application developers, who will need an understanding of the concepts presented here in order to be effective Durra application debuggers.