Using Petri Nets for Specifying Active Objects and Generative Communication

This paper presents an introduction to an approach for modelling, implementing and reasoning upon systems, based on principles of concurrent object-orientation, generative communication and Petri nets. The approach is illustrated through a case study, proposed by C. Sibertin-Blanc. The case is a variant of the well known dining philosophers problem, called "the Hurried Philosophers" problem. 1 Introduction This paper presents some results of ongoing research on combining principles of (concurrent) object-orientation, generative communication and the Petri net formalism. The combination of these three components appears to provide a sound basics for a large number of requirements for the development of complex applications and open systems 1 : flexibility and reusability, modular development, coordination of active objects, formal reasoning (both about behavioural and typetheoretical issues) upon isolated components and entire system configurations. Concurrent object-orientation is t..

Component Framework Technology for Flexible Protocol Stacks

The context of this paper and the corresponding challenges are formed by network services and their requirements to the underlying protocol stack. The relevance of this research is confirmed by three recent trends in network services and their execution environment: growing reliance of businesses and individuals on network connectivity, highly dynamic network characteristics, and a wide range of connected client device types. This paper proposes DiPS+ (Distrinet Protocol Stack+), a sophisticated software architecture and component framework to support the development of protocol stacks that are easily customizable to application- and environment-specific requirements.status: publishe

Y.: A Description Language for Composable Components

Abstract. In this paper we present CCDL, our description language for composable components. We have introduced hierarchically composable components as means to achieve finetuned customization of component based systems. A composable component is defined by a fixed contractual specification of its external view and a set of structural constraints for its internal configuration. The internal configuration of a composable component is not fixed, but will be composed according to different requirements and has to comply with the structural constraints. This permits a high degree of unanticipated variability. Our approach is architectural style specific and addresses multiflow architectures. The goal of CCDL is to describe contractual specifications and structural constraints of composable components, as guidelines for their composition. CCDL descriptions can be used by automatic composition tools that implement requirements driven composition strategies.

AO middleware supporting variability and dynamic customization of security extensions in the ORB layer

There is an increasing demand for variability and dynamic customization of middleware. Security, a key middleware service, requires variations at design-time, deploy-time as well as runtime. This is hard to achieve with state-of-the-art middleware. To handle this problem, we applied an SPL approach based on static and dynamic AO-composition in a component-based middleware platform. As proof of concept we developed a prototype with several variations in the security domain. A first evaluation shows that AO and component-based middleware are promising technologies to obtain an SPL.status: publishe

Persistency Support for Mobile Objects in the COMET Heterogeneous Environment

Open distributed computing in an internetwork environment has gained considerable attention in the past few years. This paper presents COMET, a Common Object Management EnvironmenT, that investigates basic problems associated with distributed computing in an internet environment with mobile objects. COMET's persistency support is based on typed memory, manipulated by persistent actions. The use of typed memory enables transparent handling of the presentation management issues that are unavoidable in a heterogeneous environment. Persistent actions on the other hand ensure that the typed memory is manipulated in a consistent manner. The typed memory approach presents a conceptually simple persistency model to the object programmer. The approach is general enough to be applied to other problem areas, e.g. for the realization of replicated and atomic objects. 1. Introduction In the past few years world-wide connectivity of computing equipment has become a reality. Local computing faciliti..

Using Agents for Simulating and Implementing Petri Nets

This paper presents a software architecture for simulating and implementing Petri nets. It is based on objectoriented techniques and autonomous agents. Objectorientation enables the adaptation and extension of the software architecture with new or alternatively defined features. Agents allow to model a net as a set of autonomous, cooperating entities. The result is a flexible and extendible framework of reusable components for efficiently implementing a large family of Petri net classes. The execution can be performed on a mono-processor, a parallel or distributed system. This is the result of using the XENOOPS execution environments for parallel applications. 1 Introduction Petri nets are a commonly used formalism for modelling and analysing complex concurrent systems. They make a simple, yet powerful visual formalism for describing concurrency, synchronization, causality and nondeterminism between system activities. Besides the fact that Petri nets lean themselves to deriving usefu..

Object Invocation in the COMET Open Distributed System: the Dialogue Model

This paper presents COMET, a Common Object Management EnvironmenT, that investigates basic problems associated with distributed computing in an internet environment with mobile objects. COMET offers a uniform invocation model, based on dialogues, that integrates both communication and execution aspects. On the communication side, dialogues support asynchronous invocation with preservation of causal relationships. Applications can thus take advantage of the increased parallelism that is possible in a distributed environment. Furthermore COMET's invocation model supports multiple object flavors, offering high-level functionality, s.a. persistence, replication and atomicity. This is realized by modeling invocations as flavor-specific actions, that manipulate typed memory. Reflective techniques are used to dynamically adjust dialogue algorithms according to object flavor. 1. Introduction The concept of Open Systems is becoming increasingly important in today's computing world. A typical c..