Pattern-based software architecture for service-oriented software systems

Service-oriented architecture is a recent conceptual framework for service-oriented software platforms. Architectures are of great importance for the evolution of software systems. We present a modelling and transformation technique for service-centric distributed software systems. Architectural configurations, expressed through hierarchical architectural patterns, form the core of a specification and transformation technique. Patterns on different levels of abstraction form transformation invariants that structure and constrain the transformation process. We explore the role that patterns can play in architecture transformations in terms of functional properties, but also non-functional quality aspects

Flexible Service Choreography

Service-oriented architectures are a popular architectural paradigm for building software applications from a number of loosely coupled, distributed services. Through a set of procedural rules, workflow technologies define how groups of services coordinate with one another to achieve a shared task. A problem with workflow specifications is that often the patterns of interaction between the distributed services are too complicated to predict and analyse at design-time. In certain cases, the exact patterns of message exchange and the concrete services to call cannot be predicted in advance, due to factors such as fluctuating network load or the availability of services. It is a more realistic assumption to endow software components with the ability to make decisions about the nature and scope of their interactions at runtime. Multiagent systems offer a complementary paradigm: building software applications from a number of self interested, autonomous agents. This thesis presents an investigation into fusing the agency and service-oriented architecture paradigms, in order to facilitate flexible, workflow composition. Our approach offers an agent-based solution to service choreography and is founded on the concept of shared interaction protocols. By adopting an agent-based approach to service choreography, active autonomous agents can utilise the typically passive service-oriented architectures, found in Internet and Grid systems. In contrast with statically defined, centralised service orchestrations, decentralised agents can perform service choreography at runtime, allowing them to operate in scenarios where it is not possible to define the pattern of interaction in advance. Application to real scenarios is a driving factor behind this research. By working closely with a number of active Grid projects, namely AstroGrid and the Large-Synoptic Survey Telescope (LSST), a concrete set of requirements for scientific workflow have been derived, based on realistic science problems. This research has resulted in the MultiAgent Service Choreography (MASC) language to express scientific workflow, methodology for system building and a software framework which performs agent based Web service choreography, in order to enact distributed e-Science experiments. Evaluation of this thesis is conducted through case study, applying the language, methodology and software framework to solve a motivating set of workflow scenarios

Quality-aware model-driven service engineering

Service engineering and service-oriented architecture as an integration and platform technology is a recent approach to software systems integration. Quality aspects ranging from interoperability to maintainability to performance are of central importance for the integration of heterogeneous, distributed service-based systems. Architecture models can substantially influence quality attributes of the implemented software systems. Besides the benefits of explicit architectures on maintainability and reuse, architectural constraints such as styles, reference architectures and architectural patterns can influence observable software properties such as performance. Empirical performance evaluation is a process of measuring and evaluating the performance of implemented software. We present an approach for addressing the quality of services and service-based systems at the model-level in the context of model-driven service engineering. The focus on architecture-level models is a consequence of the black-box character of services

Towards a re-engineering method for web services architectures

Recent developments in Web technologies – in particular through the Web services framework – have greatly enhanced the flexible and interoperable implementation of service-oriented software architectures. Many older Web-based and other distributed software systems will be re-engineered to a Web services-oriented platform. Using an advanced e-learning system as our case study, we investigate central aspects of a re-engineering approach for the Web services platform. Since our aim is to provide components of the legacy system also as services in the new platform, re-engineering to suit the new development paradigm is as important as re-engineering to suit the new architectural requirements

Ontology-based patterns for the integration of business processes and enterprise application architectures

Increasingly, enterprises are using Service-Oriented Architecture (SOA) as an approach to Enterprise Application Integration (EAI). SOA has the potential to bridge the gap between business and technology and to improve the reuse of existing applications and the interoperability with new ones. In addition to service architecture descriptions, architecture abstractions like patterns and styles capture design knowledge and allow the reuse of successfully applied designs, thus improving the quality of software. Knowledge gained from integration projects can be captured to build a repository of semantically enriched, experience-based solutions. Business patterns identify the interaction and structure between users, business processes, and data. Specific integration and composition patterns at a more technical level address enterprise application integration and capture reliable architecture solutions. We use an ontology-based approach to capture architecture and process patterns. Ontology techniques for pattern definition, extension and composition are developed and their applicability in business process-driven application integration is demonstrated

Semantic model-driven development of service-centric software architectures

Service-oriented architecture (SOA) is a recent architectural paradigm that has received much attention. The prevalent focus on platforms such as Web services, however, needs to be complemented by appropriate software engineering methods. We propose the model-driven development of service-centric software systems. We present in particular an investigation into the role of enriched semantic modelling for a modeldriven development framework for service-centric software systems. Ontologies as the foundations of semantic modelling and its enhancement through architectural pattern modelling are at the core of the proposed approach. We introduce foundations and discuss the benefits and also the challenges in this context