Synthesis of secure adaptors

Security is considered one of the main challenges for software oriented architectures (SOA). For this reason, several standards have been developed around WS-Security. However, these security standards usually hinder interoperability, one of the main pillars of Web service technologies. Software adaptation is a sound solution where an adaptor is deployed in the middle of the communication to overcome signature, behavioural and QoS incompatibilities between services. This is particularly important when dealing with stateful services (such as Windows Workflows or WS-BPEL processes) where any mismatch in the sequence of messages might lead the orchestration to a deadlock situation. We proposed security adaptation contracts as concise and versatile specifications of how such incompatibilities must be solved. Nonetheless, synthesising an adaptor compliant with a given contract is not an easy task where concurrency issues must be kept in mind and security attacks must be analysed and prevented. In this paper, we present an adaptor synthesis, verification and refinement process based on security adaptation contracts which succeeds in overcoming incompatibilities among services and prevents secrecy attacks. We extended the ITACA toolbox for synthesis and deadlock analysis and we integrated it with a variant of CCS, called Crypto-CCS, to verify and refine adaptors based on partial model checking and logical satisfiability techniques.     

The mediating role of psychological contract breach in IS outsourcing: inter-firm governance perspective

A substantial body of previous research on the client–vendor relationship has identified inter-organizational partnerships and formal contracts as important governance mechanisms for outsourcing performance. Successful IS development through outsourcing, however, may be more dependent on the people who execute the project in the field than on inter-firm relationships and agreed-upon formalities. Among individual-level variables, the special importance of psychological contracts has recently been noted in IS literature. This study investigates the mediating role of psychological contract breach between these two firm-level governance factors and outsourcing performance. By analyzing matched responses from project managers, vendor participants, and system users, we found that the effects of explicit legal contracts and partnership quality on outsourcing outcome are fully mediated by the client's perception of breach by the vendor. This study offers an extended theoretical perspective on the governance of firm-level collaboration, especially revealing that the benefits of formal contracts and inter-organizational partnerships eventually translate into satisfactory outsourcing outcomes for system users through each party's perception of breach on the individual level. Moreover, discrepancy was observed in this study between the client and vendor regarding the impact of legal contracts on individuals’ psychological contract while that of partnership was prominent in both sides.     

Frame Logic-based specification and discovery of semantic web services with application to medical appointments

Matching web services and client requirements in the form of goals is a significant challenge in the discovery of semantic web services. The most common but unsatisfactory approach to matching is set-based, where both the client and web services declare what objects they require and what objects they can provide. Matching then becomes the simple task of comparing sets of objects. This approach is inadequate because it says nothing about the functionality required by the client or the functionality provided by the web service. As an alternative, we use the Frame Logic as implemented in Flora-2 to specify web service capabilities and client requirements, including their preconditions, postconditions, and ontologies, implement a logic-based discovery agent using Flora-2, demonstrate its usefulness in a medical appointment making scenario, and show its efficiency both theoretically and by benchmarking. The result is an expressive yet concise representation scheme for semantic web services, and a practical, efficient, powerful, and fully implemented matching engine based purely on logical inference for web service discovery, with direct applicability to Web Service Modeling Ontology and Web Service Modeling Language, because both are based on Frame Logic.     

Dynamic and adaptive composition of e-services

The Web is rapidly becoming the platform through which many companies deliver services to businesses and individual customers. The number and type of on-line services increase day by day, and this trend is likely to continue at an even faster pace in the immediate future. Examples of e-services currently available include bill payment, delivery of customized news, or archiving and sharing of digital documents. E-Services are typically delivered individually. However, the e-service market creates the opportunity for providing value-added, integrated services, which are delivered by composing existing e-services. To support organizations in pursuing this business opportunity we have developed eFlow, a system that supports the specification, enactment, and management of composite e-services, modeled as processes that are enacted by a service process engine. Composite e-services have to cope with a highly dynamic business environment in terms of services and of service providers. In addition, the increased competition forces companies to provide customized services to better satisfy the needs of every individual customer. Ideally, service process should be able to transparently adapt to changes in the environment and to the need of different customers with minimal or no user intervention. In addition, it should be possible to dynamically modify service process definitions in a simple and effective way to manage cases where user intervention is indeed required. In this paper we show how eFlow achieves these goals.     

Web service API recommendation for automated mashup creation using multi-objective evolutionary search

Modern software development builds on external Web services reuse as a promising way that allows developers delivering feature-rich software by composing existing Web service Application Programming Interfaces, known as APIs. With the overwhelming number of Web services that are available on the Internet, finding the appropriate Web services for automatic service composition, i.e., mashup creation, has become a time-consuming, difficult, and error-prone task for software designers and developers when done manually. To help developers, a number of approaches and techniques have been proposed to automatically recommend Web services. However, they mostly focus on recommending individual services. Nevertheless, in practice, service APIs are intended to be used together forming a social network between different APIs, thus should be recommended collectively. In this paper, we introduce a novel automated approach, called SerFinder, to recommend service sets for automatic mashup creation. We formulate the service set recommendation as a multi-objective combinatorial problem and use the non-dominated sorting genetic algorithm (NSGA-II) as a search method to extract an optimal set of services to create a given mashup. We aim at guiding the search process towards generating the adequate compromise among three objectives to be optimized (i) maximize services historical co-usage, (ii) maximize services functional matching with the mashup requirements, and (iii) maximize services functional diversity. We perform a large-scale empirical experiment to evaluate SerFinder on a benchmark of real-world mashups and services. The obtained results demonstrate the effectiveness of SerFinder in comparison with recent existing approaches for mashup creation and services recommendation. The statistical analysis results provide an empirical evidence that SerFinder, significantly outperforms four state-of-the-art widely-used multi-objective search-based algorithms as well as random search.     

Interactive specification and verification of behavioral adaptation contracts

ContextAdaptation is a crucial issue when building new applications by reusing existing software services which were not initially designed to interoperate with each other. Adaptation contracts describe composition constraints and adaptation requirements among these services. The writing of this specification by a designer is a difficult and error-prone task, especially when interaction protocols are considered in service interfaces.ObjectiveIn this article, we propose a tool-based, interactive approach to support the contract design process.MethodOur approach includes: (i) a graphical notation to define port bindings, and an interface compatibility measure to compare protocols and suggest some port connections to the designer, (ii) compositional and hierarchical techniques to facilitate the specification of adaptation contracts by building them incrementally, (iii) validation and verification techniques to check that the contract will make the involved services work correctly and as expected by the designer.ResultsOur results show a reduction both in the amount of effort that the designer has to put into building the contract, as well as in the number of errors present in the final result (noticeably higher in the case of manual specification).ConclusionWe conclude that it is important to provide integrated tool support for the specification and verification of adaptation contracts, since their incorrect specification induces erroneous executions of the system. To the best of our knowledge, such tool support has not been provided by any other approach so far, and hence we consider the techniques described in this paper as an important contribution to the area of behavioral software adaptation.     

网格合同计算的有效协商机制研究

随着网格商业化的不断深入,网格计算要求：服务提供者和消费者间在组合服务中需达成端对端的高服务质量协议,高可靠性的组合服务协商机制和保障机制在网格计算中扮演着越来越重要的角色。所提出的网格合同计算模型,在组合服务过程中提供统一的用户接口,使交易双方自动动态协商满足每个单独服务的服务质量约束条件。在网格合同计算模型中,利用代理技术实现了自治网格合同计算协商机制,该协商机制遵循改进的两阶段提交FIPA协议。在服务合同中导入了软服务合同SSC和硬服务合同HSC概念,并指出动态绑定服务之前所生成的软服务合同SSC仅仅起到占位符的作用,只有在绑定时通过“硬化”才获得真实的服务承诺。     

Improving device-aware Web services and their mobile clients through an aspect-oriented,model-driven approach

ContextMobile devices have become an essential element in our daily lives, even for connecting to the Internet. Consequently, Web services have become extremely important when offering services through the Internet. However, current Web services are very inflexible as regards their invocation from different types of device, especially if we consider the need for them to be adaptable when being invoked from mobile devices.ObjectiveIn this paper, we provide an approach for the creation of flexible Web services which can be invoked transparently from different device types and which return subsequent responses, as well as providing the client’s adaptation as a result of the particular device characteristics and end-user preferences in a completely decoupled way.MethodAspect-Oriented Programming and model-driven development have been used to reduce both the impact of service and client code adaptation for multiple devices as well as to facilitate the developer’s task.ResultsA model-driven methodology can be followed from system models to code, providing the Web service developer with the option of marking which services should be adapted to mobile devices in the UML models, and obtaining the decoupled adaptation code automatically from the models.ConclusionWe can conclude that the approach presented in this paper provides us with the possibility of following the development of mobile-aware Web services in an integrated platform, benefiting from the use of aspect-oriented techniques not only for maintaining device-related code completely decoupled from the main functionality one, but also allowing a modularized non-intrusive adaptation of mobile clients to the specific device characteristics as well as to final user preferences.     

QoS contract preservation through dynamic reconfiguration: A formal semantics approach

The increasing pervasiveness of computing services in everyday life, combined with the dynamic nature of their execution contexts, constitutes a major challenge in guaranteeing the expected quality of such services at runtime. Quality of Service (QoS) contracts have been proposed to specify expected quality levels (QoS levels) on different context conditions, with different enforcing mechanisms. In this paper we present a definition for QoS contracts as a high-level policy for governing the behavior of software systems that self-adapt at runtime in response to context changes. To realize this contract definition, we specify its formal semantics and implement it in a software framework able to execute and reconfigure software applications, in order to maintain fulfilled their associated QoS contracts. The contribution of this paper is threefold. First, we extend typed-attributed graph transformation systems and finite-state machines, and use them as denotations to specify the semantics of QoS contracts. Second, this semantics makes it possible to systematically exploit design patterns at runtime by dynamically deploying them in the managed software application. Third, our semantics guarantees self-adaptive properties such as reliability and robustness in the contract satisfaction. Finally, we evaluate the applicability of our semantics implementation by integrating and executing it in FraSCAti, a multi-scale component-based middleware, in three case studies.     

A structural-semantic web service selection approach to improve retrievability of web services

Service-Oriented Computing promotes building applications by consuming and reusing Web Services. However, the selection of adequate Web Services given a client application is still a major challenge. The effort of assessing and adapting candidate services could be overwhelming due to the “impedance” of Web Service interfaces expected by clients versus the actual interfaces of retrieved Web Services. In this work, we present a novel structural-semantic approach to help developers in the retrieval and selection of services from a service registry. The approach is based on a comprehensive structural scheme for service Interface Compatibility analysis, and WordNet as the semantic support to assess identifiers of operations and parameters. We also empirically analyze, compare and contrast the performance of three service selection methods: a pure structural approach, a pure semantic approach, and the structural-semantic (hybrid) approach proposed in this work. The experimental analysis was performed with two data-sets of real-world Web Services and a service discovery support already published in the literature. Results show that our hybrid service selection approach improved effectiveness in terms of retrievability of Web Services compared to the other approaches.     

Peer to peer trade in HTM5 meta model for agent oriented cloud robotic systems

Cloud computing is a methodology and not a technology. Adaptation of cloud computing services for robotic applications is relatively straightforward while adaptation of underlying ideas will require a new design attitude. Cloud computing is a cost-effective and dynamic business model. Currently cloud robotics is understood as a client server methodology which enables robots utilize resources and services placed at centralized servers. These cloud servers treat robots as any other client computer offering them platform, infrastructure, process or algorithm as a service. HTM5 is an OMG MDA based multi-view meta-model for agent oriented development of cloud robotic systems. HTM5 encourages design of peer-to-peer service ecosystems based on an open registry and matchmaking mechanism. In peer-to-peer cloud robotics, a robot can trade its hardware, software and functional resources as a service to other robots in the ecosystem. The peer-to-peer trade in such systems may be driven by contracts and relationships between its member agents. This article discusses trade-view model of HTM5 methodology and its use in developing a cloud robotic ecosystem that implements peer-to-peer, contract based economy. The article also presents a case study with experiments that implement distributed artificial intelligence and peer-to-peer service oriented trade on simulated and real robot colonies.     

Towards a reference service model for the Web of Services

This paper introduces a reference service model (RSM) that closes the gap between two phenomenically contradictory service annotation paradigms: traditional semantic service frameworks and the emerging social annotation of services. RSM aims to (i) facilitate the semantic interlinking between services annotated using different semantic models and (ii) accommodate the bottom-up social annotation of services. RSM was developed following the design science research methodology. To develop RSM, existing semantic service models and SOA service models were reviewed in the light of the six service contracts and examined whether and using which elements each of the models supports in each of the contracts. The identified elements were then fed to a multiphase abstraction exercise. RSM comprises of the following concepts: Service, Service Input, Service Output, Service Context and Service Logic, Service Provider, Service Client and Service Feedback. The paper also maps the concepts of RSM to those of existing semantic service models and positions RSM with respect to related SOA service models. Finally, an implementation of RSM in OWL and two pilot developments that highlight different aspects of RSM are discussed.     

FRWSC: a framework for robust Web service composition

The deployment of Web services in a highly dynamic environment brings about a number of research challenges. In dynamic Web services composition, failures and changes to atomic services cannot be detected before invocation. Hence, the failure or even the change in an atomic service may lead to the overall failure of the composite service. In addition, SOAP error code is not sufficient for the client to analyze the failure reason and handle it. In this work, we introduce a framework to deal with unexpected failures during runtime composition. The proposed framework is built on top of composite services stack as an interface between the composite service and its external service partners. The evaluation results show that by using the proposed framework, it is possible to avoid composite service failures that are caused by changes or failures in atomic services.