Interface refactoring in performance-constrained web services

This paper presents the development of REF-WS an approach to enable a Web Service provider to reliably evolve their service through the application of refactoring transformations. REF-WS is intended to aid service providers, particularly in a reliability and performance constrained domain as it permits upgraded ’non-backwards compatible’ services to be deployed into a performance constrained network where existing consumers depend on an older version of the service interface. In order for this to be successful, the refactoring and message mediation needs to occur without affecting functional compatibility with the services’ consumers, and must operate within the performance overhead expected of the original service, introducing as little latency as possible. Furthermore, compared to a manually programmed solution, the presented approach enables the service developer to apply and parameterize refactorings with a level of confidence that they will not produce an invalid or ’corrupt’ transformation of messages. This is achieved through the use of preconditions for the defined refactorings

Flexible coordination techniques for dynamic cloud service collaboration

The provision of individual, but also composed services is central in cloud service provisioning. We describe a framework for the coordination of cloud services, based on a tuple‐space architecture which uses an ontology to describe the services. Current techniques for service collaboration offer limited scope for flexibility. They are based on statically describing and compositing services. With the open nature of the web and cloud services, the need for a more flexible, dynamic approach to service coordination becomes evident. In order to support open communities of service providers, there should be the option for these providers to offer and withdraw their services to/from the community. For this to be realised, there needs to be a degree of self‐organisation. Our techniques for coordination and service matching aim to achieve this through matching goal‐oriented service requests with providers that advertise their offerings dynamically. Scalability of the solution is a particular concern that will be evaluated in detail

An evaluation framework for assessing the dependability of Dynamic Binding in Service-Oriented Computing

Service-Oriented Computing (SOC) provides a flexible framework in which applications may be built up from services, often distributed across a network. One of the promises of SOC is that of Dynamic Binding where abstract consumer requests are bound to concrete service instances at runtime, thereby offering a high level of flexibility and adaptability. Existing research has so far focused mostly on the design and implementation of dynamic binding operations and there is little research into a comprehensive evaluation of dynamic binding systems, especially in terms of system failure and dependability. In this paper, we present a novel, extensible evaluation framework that allows for the testing and assessment of a Dynamic Binding System (DBS). Based on a fault model specially built for DBS's, we are able to insert selectively the types of fault that would affect a DBS and observe its behavior. By treating the DBS as a black box and distributing the components of the evaluation framework we are not restricted to the implementing technologies of the DBS, nor do we need to be co-located in the same environment as the DBS under test. We present the results of a series of experiments, with a focus on the interactions between a real-life DBS and the services it employs. The results on the NECTISE Software Demonstrator (NSD) system show that our proposed method and testing framework is able to trigger abnormal behavior of the NSD due to interaction faults and generate important information for improving both dependability and performance of the system under test

Practical Assessment Scheme to Service Selection for SOC-­based Applications

Service ­Oriented Computing promotes building applications by consuming reusable services. However, facing the selection of adequate services for a specific application still is a major challenge. Even with a reduced set of candidate services, the assessment effort could be overwhelming. On a previous work we have presented a novel approach to assist developers on discovery, selection and integration of services. This paper presents the selection method, which is based on a comprehensive scheme for services' interfaces compatibility. The scheme allows developers to gain knowledge on likely services' interactions and their required adaptations to achieve a positive integration. The scheme is also complemented by a framework based on black­box testing to verify compatibility on the expected behavior of a candidate service. The usefulness of the selection method is highlighted through a series of case studies.Sociedad Argentina de Informática e Investigación Operativ

Self-supervising BPEL Processes

Service compositions suffer changes in their partner services. Even if the composition does not change, its behavior may evolve over time and become incorrect. Such changes cannot be fully foreseen through prerelease validation, but impose a shift in the quality assessment activities. Provided functionality and quality of service must be continuously probed while the application executes, and the application itself must be able to take corrective actions to preserve its dependability and robustness. We propose the idea of self-supervising BPEL processes, that is, special-purpose compositions that assess their behavior and react through user-defined rules. Supervision consists of monitoring and recovery. The former checks the system's execution to see whether everything is proceeding as planned, while the latter attempts to fix any anomalies. The paper introduces two languages for defining monitoring and recovery and explains how to use them to enrich BPEL processes with self-supervision capabilities. Supervision is treated as a cross-cutting concern that is only blended at runtime, allowing different stakeholders to adopt different strategies with no impact on the actual business logic. The paper also presents a supervision-aware runtime framework for executing the enriched processes, and briefly discusses the results of in-lab experiments and of a first evaluation with industrial partners

An Evaluation on Developer’s Acceptance of EasySOC : A Development Model for Service-Oriented Computing

Different development methods have been proposed for enabling the construction of software with the Service-Oriented Computing (SOC) paradigm . Service-oriented applications invoke services that developers must first discover, engage, and in time potentially replace with newer versions or even alternative services from differentproviders. Hence, the widely agreed development methodology involves three main activities, including service discovery, service incorporation into applications, and service replacement. EasySOC is a very recent approach for developing service-oriented applications that decreases the costs of building this kind of applications, by simplifyingdiscovery, integration and replacement of services. This paper reports some experiments evidencing the effort needed to start producing service –oriented applications with EasySOC. Result s show that users non experienced in SOC development perceive that EasySOC is convenient and easy to adopt.Sociedad Argentina de Informática e Investigación Operativ

Design time detection of architectural mismatches in service oriented architectures

Service Oriented Architecture (SOA) is a software component paradigm that has the potential to allow for exible systems that are loosely coupled to each other. They are discoverable entities that may be bound to at run time by a client who is able to use the service correctly by referring to the service's description documents. Assumptions often have to be made in any design process if the problem domain is not fully speci ed. If those decisions are about the software architecture of that component and it is inserted into a system with di ering and incompatible assumptions then we say that an architectural mismatch exists. Architectural styles are a form of software reuse. They can simply be used by referring to a name such as \client-server" or \pipe and lter", where these names may conjure up topologies and expected properties in the architects mind. They can also however be more rigorously de ned given the right software environment. This can lead to a vocabulary of elements in the system, de ned properties of those elements along with rules and analysis to either show correctness of an implementation or reveal some emergent property of the whole. SOA includes a requirement that the service components make available descriptions of themselves, indicating how they are to be used. With this in mind and assuming we have a suitable description of the client application it should be the case that we can detect architectural mismatches when designing a new system. Here designing can range from organising a set of existing components into a novel con guration through to devising an entirely new set of components for an SOA. This work investigates the above statement using Web Services as the SOA implementation and found that, to a degree, the above statement is true. The only element of description required for a web service is the Web Service Description Language (WSDL) document and this does indeed allow the detection of a small number of mismatches when represented using our minimal web service architectural style. However from the literature we nd that the above mismatches are only a subset of those that we argue should be detectable. In response to this we produce an enhanced web service architectural style containing properties and analysis supporting the detection of this more complete set of mismatches and demonstrate its e ectiveness against a number of case studies.EThOS - Electronic Theses Online ServiceGBUnited Kingdo