Aspect-Oriented Techniques for Web Services: a Model-Driven Approach

Web Service technologies offer a successful way for interoperability among applications, but in order to tackle the entire web service life cycle, it is necessary to face how to model systems based on service functionality and also how to add extra-functional properties to modelled services. In this regard, we propose first of all a versatile and simple UML profile based on the Service Component Architecture specification for modelling services, in order to provide a model environment in which to add extra-functional properties. Secondly, a new UML profile is proposed to model and reuse the said extra-functional properties in service models. The implemented models based on these profiles will be independent from a final implementation language or platform, thus it is necessary to specify a particular type of model to convert the independent one into in a subsequent step. In order to meet this requirement an object, an aspect and a policy based models are proposed as the intermediate step between the independent model and the final code. We acknowledge that there are tools available which convert Java models into web services\u27 Java code, and it is not our aim to build a tool to fulfil this requirement. Regarding extra-functional properties, aspect-oriented techniques allow them to be easily modularized and reused; in this respect, properties are implemented as aspects in a totally transparent way and avoid the need to modify service code in an intrusive manner on adding extra-functional properties, improving our system maintenance. Furthermore, this way traceability between the model and the code is perfectly maintained in both directions. This work has been developed thanks to the support of CICYT under contract TIN2005-09405-C02-02

A resource-oriented architecture for business process systems

Background: The REpresentational State Transfer (REST) design principles treat all concepts in the world as link-connected resources, and support ROA (Resource-Oriented Architecture) for the Web applications. REST and ROA are responsible for the adaptability achieved in the Web. Some design approaches of Web-based business process systems recently evolved towards RESTful to inherit adaptability. However, none of the approaches can improve the adaptability of the produced systems. Aims: Propose a systematic approach for design and execution of Web-based business processes to improve adaptability of the produced systems. Methods: This research followed an empirical research methodology, which evaluates research solutions with real-world cases. On one hand, the research solution was derived by 1) tailoring the REST principles towards business process systems; 2) proposing REST annotations on existing business process modelling; 3) mapping the concepts of business process to HTTP/URI specifications; and 4) designing a format for process context information. On the other hand, the research solution was evaluated through three real-world case studies. Two of the case studies conducted comparative analysis in terms of adaptability of the systems produced by the proposed approach and two alternatives, namely, SOA and MEST (MESsage Transfer). The analysis is based on metrics, including LOC difference, change locality, coupling and cohesion, and an analysis framework called BASE. Results: The research solution is ROA4BP, which includes 1) an architecting approach for design and implementation of Web-based business processes to provide a development guideline; 2) a set of REST-related annotations on existing process modelling to ensure the compatibility with existing techniques; 3) A systematic mapping between business process and HTTP/URI specifications to utilize the advanced mechanisms provided by the Web infrastructure; and 4) a communication format to exchange structured process context information during runtime among process participants. A modelling tool, a programming API and a runtime engine were implemented to support the approach and simplify the implementation of case studies. The case studies demonstrated that ROA4BP can produce more adaptable business process systems compared to the other two alternatives. Conclusion: ROA4BP can help to design and execute RESTful business process systems with better adaptability at design-time and runtime

A detailed investigation of interoperability for web services

The thesis presents a qualitative survey of web services' interoperability, offering a snapshot of development and trends at the end of 2005. It starts by examining the beginnings of web services in earlier distributed computing and middleware technologies, determining the distance from these approaches evident in current web-services architectures. It establishes a working definition of web services, examining the protocols that now seek to define it and the extent to which they contribute to its most crucial feature, interoperability. The thesis then considers the REST approach to web services as being in a class of its own, concluding that this approach to interoperable distributed computing is not only the simplest but also the most interoperable. It looks briefly at interoperability issues raised by technologies in the wider arena of Service Oriented Architecture. The chapter on protocols is complemented by a chapter that validates the qualitative findings by examining web services in practice. These have been implemented by a variety of toolkits and on different platforms. Included in the study is a preliminary examination of JAX-WS, the replacement for JAX-RPC, which is still under development. Although the main language of implementation is Java, the study includes services in C# and PHP and one implementation of a client using a Firefox extension. The study concludes that different forms of web service may co-exist with earlier middleware technologies. While remaining aware that there are still pitfalls that might yet derail the movement towards greater interoperability, the conclusion sounds an optimistic note that recent cooperation between different vendors may yet result in a solution that achieves interoperability through core web-service standards

A web API ecosystem through feature based reuse

The fast-growing web API landscape brings clients more options than ever before-in theory. In practice, they cannot easily switch between different providers offering similar functionality. We discuss a vision for developing web APIs based on reuse of interface parts called features. Through the introduction of five design principles, we investigate the impact of feature-based reuse on web APIs. Applying these principles enables a granular reuse of client and server code, documentation, and tools. Together, they can foster a measurable ecosystem with cross-API compatibility, opening the door to a more flexible generation of web clients

A web API ecosystem through feature based reuse

The fast-growing web API landscape brings clients more options than ever before-in theory. In practice, they cannot easily switch between different providers offering similar functionality. We discuss a vision for developing web APIs based on reuse of interface parts called features. Through the introduction of five design principles, we investigate the impact of feature-based reuse on web APIs. Applying these principles enables a granular reuse of client and server code, documentation, and tools. Together, they can foster a measurable ecosystem with cross-API compatibility, opening the door to a more flexible generation of web clients

Automation Hooks Architecture Trade Study for Flexible Test Orchestration

We describe the conclusions of a technology and communities survey supported by concurrent and follow-on proof-of-concept prototyping to evaluate feasibility of defining a durable, versatile, reliable, visible software interface to support strategic modularization of test software development. The objective is that test sets and support software with diverse origins, ages, and abilities can be reliably integrated into test configurations that assemble and tear down and reassemble with scalable complexity in order to conduct both parametric tests and monitored trial runs. The resulting approach is based on integration of three recognized technologies that are currently gaining acceptance within the test industry and when combined provide a simple, open and scalable test orchestration architecture that addresses the objectives of the Automation Hooks task. The technologies are automated discovery using multicast DNS Zero Configuration Networking (zeroconf), commanding and data retrieval using resource-oriented Restful Web Services, and XML data transfer formats based on Automatic Test Markup Language (ATML). This open-source standards-based approach provides direct integration with existing commercial off-the-shelf (COTS) analysis software tools

iSemServ : a framework for engineering intelligent semantic services

The need for modern enterprises and Web users to simply and rapidly develop and deliver platform-independent services to be accessed over the Web by the global community is growing. This is self-evident, when one considers the omnipresence of electronic services (e-services) on the Web. Accordingly, the Service-Oriented Architecture (SOA) is commonly considered as one of the de facto standards for the provisioning of heterogeneous business functionalities on the Web. As the basis for SOA, Web Services (WS) are commonly preferred, particularly because of their ability to facilitate the integration of heterogeneous systems. However, WS only focus on syntactic descriptions when describing the functional and behavioural aspects of services. This makes it a challenge for services to be automatically discovered, selected, composed, invoked, and executed – without any human intervention. Consequently, Semantic Web Services (SWS) are emerging to deal with such a challenge. SWS represent the convergence of Semantic Web (SW) and WS concepts, in order to enable Web services that can be automatically processed and understood by machines operating with limited or no user intervention. At present, research efforts within the SWS domain are mainly concentrated on semantic services automation aspects, such as discovery, matching, selection, composition, invocation, and execution. Moreover, extensive research has been conducted on the conceptual models and formal languages used in constructing semantic services. However, in terms of the engineering of semantic services, a number of challenges are still prevalent, as demonstrated by the lack of development and use of semantic services in real-world settings. The lack of development and use could be attributed to a number of challenges, such as complex semantic services enabling technologies, leading to a steep learning curve for service developers; lack of unified service platforms for guiding and supporting simple and rapid engineering of semantic services, and the limited integration of semantic technologies with mature service-oriented technologies. vi In addition, a combination of isolated software tools is normally used to engineer semantic services. This could, however, lead to undesirable consequences, such as prolonged service development times, high service development costs, lack of services re-use, and the lack of semantics interoperability, reliability, and re-usability. Furthermore, available software platforms do not support the creation of semantic services that are intelligent beyond the application of semantic descriptions, as envisaged for the next generation of services, where the connection of knowledge is of core importance. In addressing some of the challenges highlighted, this research study adopted a qualitative research approach with the main focus on conceptual modelling. The main contribution of this study is thus a framework called iSemServ to simplify and accelerate the process of engineering intelligent semantic services. The framework has been modelled and developed, based on the principles of simplicity, rapidity, and intelligence. The key contributions of the proposed framework are: (1) An end-to-end and unified approach of engineering intelligent semantic services, thereby enabling service engineers to use one platform to realize all the modules comprising such services; (2) proposal of a model-driven approach that enables the average and expert service engineers to focus on developing intelligent semantic services in a structured, extensible, and platform-independent manner. Thereby increasing developers’ productivity and minimizing development and maintenance costs; (3) complexity hiding through the exploitation of template and rule-based automatic code generators, supporting different service architectural styles and semantic models; and (4) intelligence wrapping of services at message and knowledge levels, for the purposes of automatically processing semantic service requests, responses and reasoning over domain ontologies and semantic descriptions by keeping user intervention at a minimum. The framework was designed by following a model-driven approach and implemented using the Eclipse platform. It was evaluated using practical use case scenarios, comparative analysis, and performance and scalability experiments. In conclusion, the iSemServ framework is considered appropriate for dealing with the complexities and restrictions involved in engineering intelligent semantic services, especially because the amount of time required to generate intelligent semantic vii services using the proposed framework is smaller compared with the time that the service engineer would need to manually generate all the different artefacts comprising an intelligent semantic service. Keywords: Intelligent semantic services, Web services, Ontologies, Intelligent agents, Service engineering, Model-driven techniques, iSemServ framework.ComputingD. Phil. (Computer science

Comprehensive service semantics and light-weight Linked Services: towards an integrated approach

Semantics are used to mark up a wide variety of data-centric Web resources but, are not used in significant numbers to annotate online services — that is despite considerable research dedicated to Semantic Web Services (SWS). This is partially due to the complexity of comprehensive SWS models aiming at automation of service-oriented tasks such as discovery, composition, and execution. This has led to the emergence of a new approach dubbed Linked Services which is based on simplified service models that are easier to populate and interpret and accessible even to non-experts. However, such Minimal Service Models so far do not cover all execution-related aspects of service automation and merely aim at enabling more comprehensive service search and clustering. Thus, in this paper, we describe our approach of combining the strengths of both distinct approaches to modeling Semantic Web Services – “lightweight” Linked Services and “heavyweight” SWS automation – into a coherent SWS framework. In addition, an implementation of our approach based on existing SWS tools together with a proof-of-concept prototype used within the EU project NoTube is presented

The Many Facets of Mediation: A Requirements-driven Approach for Trading-off Mediation Solutions

Mediation aims at enabling dynamic composition of multi- ple components by making them interact successfully in order to satisfy given requirements. Through dynamic composition, software systems can adapt their structure and behaviour in dynamic and heterogeneous envi- ronments such as ubiquitous computing environments. This paper pro- vides a review of existing mediation approaches and their key character- istics and limitations. We claim that only a multifaceted approach that brings together and enhances the solutions of mediation from different perspectives is viable in the long term. We discuss how requirements can help identify synergies and trade-offs between these approaches and drive the selection of the appropriate mediation solution. We also highlight the open issues and future research directions in the area