Dennis L. Doubleday

Durra: a structure description language for developing distributed applications

Durra is a language and runtime support system for developing distributed applications. In this paper, we describe the general nature of these applications, and the need for separating structural and behavioural details. A Durra user describes an application as a set of components (application tasks and communication channels), a set of alternative configurations showing how these components are connected at runtime, and a set of conditional configuration transitions that take place at runtime. We illustrate these features through examples drawn from the fault tolerance domain. We conclude with an illustration of the use of Durra in an incremental software development scenario.

Application-level programming

The use of a declarative language, called Dura, designed to support application-level programming is illustrated by distributed avionics system. The authors show how the language is used to describe the application, its components and structure; how the run-time executive provides support for fault-tolerance by reconfiguration of the application; and how an interactive interface to the executive supports debugging and monitoring of the application.<<ETX>>

Building distributed Ada applications from specifications and functional components

Abstract : Durra is a language and support environment for the specification and execution of distributed Ada applications. A Durra programmer describes an application as a collection of processes and data links. More complicated application descriptions may also include a structuring of this collection that varies dynamically according to a set of reconsideration conditions. Each process defined in the application description is associated with an independently complied Ada subprogram that implements the behavior of that process. The Durra programmer specifies the distribution of application components by assigning them to virtual nodes called clusters. For each cluster, the Durra compiler generates a multithreaded Ada program that imports the code for the processes assigned to that node and manages their execution. Durra also facilitates rapid prototyping through the use of tools that interpret timing specifications associated with processes and generates Ada code to simulate their expected behavior.