Apostolos V. Zarras

Service-oriented middleware for the Future Internet: state of the art and research directions

Service-oriented computing is now acknowledged as a central paradigm for Internet computing, supported by tremendous research and technology development over the last 10 years. However, the evolution of the Internet, and in particular, the latest Future Internet vision, challenges the paradigm. Indeed, service-oriented computing has to face the ultra large scale and heterogeneity of the Future Internet, which are orders of magnitude higher than those of today’s service-oriented systems. This article aims at contributing to this objective by identifying the key research directions to be followed in light of the latest state of the art. This article more specifically focuses on research challenges for service-oriented middleware design, therefore, investigating service description, discovery, access, and composition in the Future Internet of services.

A dynamic reconfiguration service for CORBA

Providing software qualities such as availability, adaptability and maintainability to long-running distributed applications forms a major challenge for the configuration management of a software system. Modifications of a systems structure are expected to happen on-the-fly, to cause minimum execution disruption and to be effected in a way that preserves a consistent state of the participating entities. This paper presents a novel algorithm for performing consistent dynamic reconfiguration of CORBA applications, where consistency refers to RPC integrity. The novelty of the algorithm is that it passivates the links affected by the reconfiguration, which causes the node activities that use them to block but does not result in blocking the entire node. The consequent execution disruption is minimal, a fact that is practically verified by a performance evaluation done in a number of different reconfiguration scenarios.

CoWSAMI: Interface-aware context gathering in ambient intelligence environments

In this paper we present CoWSAMI, a middleware infrastructure that enables context awareness in open ambient intelligence environments, consisting of mobile users and context sources that become dynamically available as the users move from one location to another. A central requirement in such dynamic scenarios is to be able to integrate new context sources and users at run-time. CoWSAMI exploits a novel approach towards this goal. The proposed approach is based on utilizing Web services as interfaces to context sources and dynamically updatable relational views for storing, aggregating and interpreting context. Context rules are employed to provide mappings that specify how to populate context relations, with respect to the different context sources that become dynamically available. An underlying context sources discovery mechanism is utilized to maintain context information up to date as context sources, and users get dynamically involved.

Model-Driven Dependability Analysis of WebServices

This paper focuses on the development of a principled methodology for the dependability analysis of composite Web services. The first step of the methodology involves a UML representation for the architecture specification of composite Web services. The proposed representation is built upon BPEL and introduces necessary extensions to support the second step of the methodology, which comprises the specification of properties, characterizing the failure behavior of the elements that constitute the composite Web services. The automated mapping of this extended UML model to Block Diagrams and Markov models is introduced as the third step of the methodology. A comparative analysis of the aforementioned dependability analysis techniques in terms of precision and complexity is also performed.

A framework for systematic synthesis of transactional middleware

Transactions are contracts that guarantee a consistent, transparent, individual system state transition and their use is widespread in many different kinds of computing systems. Some well known standards (e.g. Corba) include the specification of services that provide transactional properties. In this paper, we present a formal method for the systematic synthesis of transactional middleware based on the combination of the aforementioned services. The synthesis of transactional middleware is based on (i) the formal specification of transactional properties and (ii) stub code generation.

Systematic aid for developing middleware architectures

This development environment enables the specification, automated composition, and quality analysis of flexible, configurable middleware architectures, notably in distributed systems.

Dynamic Service Substitution in Service-Oriented Architectures

The problem we deal with in this paper is the dynamic substitution of stateful services that become unavailable during the execution of service orchestrations. Previous research efforts focusing on the reconfiguration of conventional distributed systems enable the substitution of system entities with other prefabricated passive entities that serve as a backup. Nevertheless, the problem of service substitution is far more complex. In SOA, we can assume the possible existence of several semantically compatible services capable of performing the same or similar tasks. However, each one of them constantly serves requests and cannot be considered as a passive backup for other services. Therefore, we propose the SIROCO middleware platform, enabling the runtime, semantic-based service substitution. The basic concepts of SIROCO are discussed along with an experimental evaluation of our first prototype. Our findings show that SIROCO provides the necessary means for achieving dynamic service substitution with a reasonable expense on the execution of service orchestrations.

Multi-view description of software architectures

The specification of a software architecture using different ADLs allows system designers to carry out a number of complementary analyses. In this position paper, we go one step further in this direction by advocating the need for specifying distinct views of a software architecture, each characterizing a specific type of properties (i.e. functional, interaction, and quality properties). Multi-view description of a software architecture raises the issue of combining a set of architectural views so as to derive the resulting overall architecture. We propose some hints on how this can be handled.

A Comparison Framework for Middleware Infrastructures.

Middleware is a software layer standing between the operating system and the application, enabling the transparent integration of distributed objects. In this paper, we propose a framework that facilitates the comparison of middleware infrastructures. Our approach serves for identifying similarities and differences between middleware infrastructures and revealing their advantages and disadvantages when facing the question of choosing one that satisfies the application’s requirements. Based on the proposed framework, we compare CORBA with J2EE and COM+, three of the most widely used infrastructures in both industry and academia.

An integrated development and runtime environment for the future internet

The Future Internet environments raise challenging issues for the Service-Oriented Architectures. Due to the scalability and heterogeneity issues new approaches are thought in order to leverage the SOA to support a wider range of services and users. The CHOReOS project is part of the European Community Initiative to sketch technological solutions for the future ultra large systems. In particular, CHOReOS explores the choreography of services paradigm. Within this project, a conceptual architecture combining both the development and runtime environments is realized. This chapter introduces the CHOReOS Integrated Development and Runtime Environment, aka IDRE.