The development of real-time distributed applications requires middleware providing both reliability and performance. Middleware must be adaptable to meet application requirements and integrate legacy components. Current middleware provides only partial solutions to these issues. Moreover, they newer address all of them. Thus, a new generation of middleware is required. We have introduced the schizophrenic middleware concept as an integrated solution to build versatile reliable distributed applications. PolyORB, our implementation of schizophrenic middleware, supports various distribution models: CORBA (Common Object Request Broker Architecture), SOAP (Simple Object Access Protocol), DSA (Ada 95 Distributed System Annex), Message Passing (an adaptation of Java Message Service to Ada 95) and Web Server paradigm (close to what AWS offers). In this paper, we describe the implementation of PolyORB and provide a summary of our experience regarding the issues mentioned above. in a wide range of systems (embedded, mobile or real-time systems) increases the multiplication of distribution models with some specific variations.Each application comes with its specific needs and takes advantage of one distribution model. But all these applications (possibly based on heterogeneous distribution models) have to interoperate one with another. Middleware usually handles interoperability between heterogeneous hardware or operating systems. In the context of heterogeneous components interactions, middleware has to propose a new form of interoperability on which this paper focuses e.g. an interoperability between distribution models. This property is summarized as Middleware to Middleware interaction (M2M) [Bak01].Designing from scratch specific middleware for a variant of distribution model, driven by particular application requirements, would be too expensive. A better approach consists of designing general middleware that can be tailored to the specific application needs. This saves both time and money.Configurable or generic middleware provides a first efficient solution to tailor these distribution platforms so that they meet the application needs: TAO [SC97] can be configured to address real-time concerns, and Jonathan [DHTS98] can be personalized for various distribution models. But such middleware does not provide interoperability between existing components based on different distribution models. Yet this issue cannot be discarded since distributed systems now commonly reuse legacy components.We have introduced the schizophrenic middleware concept [QPK01] as a global solution to both configurability to meet application requirements, adaptability of distribution mechanisms and interoperability between distribution models. It also provides support for execution determinism and formal verification. PolyORB [PQK + 01], our implementation of such middleware, is a proof of concept.The aim of this paper is to describe the schizophrenic concepts and the associated architecture. We study the PolyORB implementation and demonstrate the...
Abstract. Developing safety-critical distributed applications is a difficult challenge. A failure may cause important damages as loss of human life or mission's failure. Such distributed applications must be designed and built with rigor. Reducing the tedious and error-prone development steps is required; we claim that automatic code generation is a natural solution. In order to ease the process of verification and certification, the user can use modeling languages to describe application critical aspects. In this paper we introduce the use of AADL as a modeling language for Distributed Real-time Embedded (DRE) systems. Then we present our tool-suite OCARINA which allows automatic code generation from AADL models. Finally, we present a comparison between OCARINA and traditional approaches.
Safety-critical systems are widely used in different domains and lead to an increasing complexity. Such systems rely on specific services such space and time isolation as in the ARINC653 avionics standard. Their criticality requires a carefully driven design based on an appropriate development process and dedicated tools to detect and avoid problems as early as possible.Model Driven Engineering (MDE) approaches are now considered as valuable approach for building safety-critical systems. The Architecture Analysis and Design Language (AADL) proposes a component-based language suitable to operate MDE that fits with safety-critical systems needs. This paper presents an approach for the modeling, verification and implementation of ARINC653 systems using AADL. It details a modeling approach exploiting the new features of AADL version 2 for the design of ARINC653 architectures. It also proposes modeling patterns to represent other safety mechanisms such as the use of Ravenscar for critical applications. This approach is fully backed by tools with Ocarina (AADL toolsuite), POK (AADL/AR-INC653 runtime) and Cheddar (scheduling verification). Thus, it assists system engineers to simulate and validate non functional requirements such as scheduling or resources dimensioning.
Building distributed deal-time embedded systems requires a stringent methodology, from early requirement capture to full implementation. However, there is a strong link between the requirements and the final implementation (e.g., scheduling and resource dimensioning). Therefore, a rapid prototyping process based on automation of tedious and error-prone tasks (analysis and code generation) is required to speed up the development cycle. In this article, we show how the AADL ( Architecture Analysis and Design Language ), which appeared in late 2004, helps solve these issues thanks to a dedicated tool suite. We then detail the prototyping process and its current implementation: Ocarina.
Abstract.Esterel is an imperative synchronous language designed for the specification and the development of reactive systems. Recent studies pointed out that its use for the development of avionics software can yield great benefits but that the lack of support for separate compilation in the current toolset may be an obstacle to the development of large systems. This paper presents the Cronos framework which provides such support for some specific cases of Esterel programs.
This paper describes how GLADE, our implementation of the Ada 95 Distributed Systems Annex, can be used to build large object-oriented real-time distributed systems. In addition to the powerful distribution features included in the Ada 95 language itself, we provide extensions to help the programmer build robust and failsafe distributed applications.
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