Michel Riveill

Architecturing and configuring distributed application with Olan

Middleware platforms are today solutions to the problem of designing and implementing distributed applications. They provide facilities for heterogeneous software components to communicate remotely, according to various interaction model, for example client server communication or asynchronous message passing. However, middleware platforms, like message busses or object request brokers, hardly provide tools for the design, configuration and installation of complex software architectures. This paper presents the Olan environment which primary objective is the description of complex architecture, their configuration according to application requirements and the deployment on heterogeneous distributed environments. The Olan environment is based on an Architecture Description Language where the application is considered as a hierarchy of interconnected software components. A set of software engineering tools assist the application designer in his task of wrapping existing software modules into components which are in turned interconnected through various communication models and finally assembled together according to specific configuration criteria. At run time, a set of system services in charge of automating the installation of the components and their communication channels on a given middleware platform, thus facilitating the overall deployment process of the global application.

Component-Based Programming and Application Management with Olan

Efficient system mechanisms for distributed object management are becoming increasingly available. Application developers need appropriate tools to fully exploit the power of these facilities. A distributed application is conveniently viewed as a set of components, some of which are developed specifically, while others are legacy applications, encapsulated within components. While engineering issues for the development of individual components are reasonably understood, many research issues are open in the management of software configurations made up of a number of distributed components. In this paper, we introduce a component-based programming model supported by a module interconnection language for large scale distributed application development and administration. The contribution of the Olan model is to separate the interconnection requirements of the application from the implementation and from the constraints of the underlying architecture. The flexibility of this model is well suited to large scale application requirements in terms of components distribution and dynamic evolution. As a first experiment, we have developed a teleconferencing application, whose description highlights the advantages of our approach.

A synchronization mechanism for an object oriented distributed system

A mechanism for synchronizing shared objects in a distributed system based on persistent, typed objects is presented. Synchronization constraints are expressed as separate control clauses and are factorized for a class of objects. The interference of this mechanism with inheritance and transactions is examined and solutions are proposed. Examples of synchronized objects are provided, and a semaphore-based implementation of the mechanism is described.<<ETX>>

The Guide Language

The Guide language is an object-oriented language dedicated for programming distributed applications on top of the Comandos platform. This language faithfully reflects all the capabilities of the Comandos model. It combines the facilities of a strongly typed object model with a powerful computational model. Key features of the language are: separation between types and classes, conformant subtyping, distribution transparency, concurrent activities, synchronization mechanism for shared objects, and exception handling. This paper presents the design choices for the Guide language and discusses programming experience gained from the use of the language for the construction of distributed applications.

Experience with object-based distributed computation in the GUIDE operating system

A brief description is given of how the issues of access to (possibly remote) services and cooperative distributed computing are treated in GUIDE (Grenoble universities integrated distributed environment), a distributed operating system under development at Grenoble on a local network of workstations. An overview of the project is given, and the computational model of the system is described. Remote computation is discussed. The current implementation status and experience with the system are examined.<<ETX>>

A Step Towards the Client/Server Model: The OODE Approach

This paper describes the main functionalities of the OODE (Object Oriented Distributed Environment) platform which facilitates the development of distributed and cooperative applications using persistent objects. The compatibility with the OMG and CORBA is also discussed.