A Novel Process Network Model for Interacting Context-Aware Web Services

PurposeIn the last decade, web services have become a major technology to implement loosely coupled business processes and perform application integration. Through the use of context, a new generation of web services, namely context‐aware web services (CASs), is currently emerging as an important technology for building innovative context‐aware applications. Unfortunately, CASs are still difficult to build. Issues like lack of context provisioning management approach and lack of generic approach for formalizing the development process need to be solved in the first place for easy and effective development of CASs. The purpose of this paper is to investigate the techniques on developing CASs.Design/methodology/approachThe paper focuses on introducing a model‐driven platform, called ContextServ, and showcasing how to use this platform to rapidly develop a context‐aware web application, Smart Adelaide Guide. ContextServ adopts a model‐driven development (MDD) approach where a Unified Modeling Language (UML)‐based modeling language – ContextUML – is used to model web services and its context‐awareness features.FindingsThe paper presents novel techniques for efficient and effective development of CASs using a MDD approach. The ContextServ platform is the only one that provides a comprehensive software toolset that supports graphical modeling and automatic model transformation of CASs.Practical implicationsThe proposed approach has been validated in practice by developing various CASs. The experimental study demonstrates the efficiency and effectiveness of the approach.Originality/valueThe paper presents a novel platform called ContextServ, which offers a set of visual editing and automation tools for easy and fast generating and deploying CASs.

In web service based dynamic E-commerce applications, inclusion of context-aware features in the delivered services is an important approach to improve the efficiency of the dialogues between users and systems. In this paper, we explore a novel context-aware web service composition model for dynamic E-commerce applications, aims to effectively process and take advantage of contexts and facilitate the development of context-aware E-commerce applications. We present a context-aware composition model of web services for E-commerce applications based on a formal model, Context-aware Process Network (CAPN), which is a dataflow and channel based model of cooperative computation. We extend the Context-aware Process Network to a context-aware web service composition model named ECModel by adding a kind of sensor processes which is used to catch contextual data from external environment. Through modeling the register link's behaviors, we present how a web service can respond to its context changes dynamically. We describe formal behavior semantics of ECModel and realize context-awareness in this model. We also present a composition framework of dynamic E-commerce based on ECModel.

Context-awareness is gaining wide importance, especially when targeting pervasive environments, whereas Web Services are often exploited as building blocks of context-aware applications because of their interoperability properties. In this framework, Web Services can be used as business services requiring context data for their functionality, but also as context sources offering access to context information. Combining the development of context-aware Web Services with Model-Driven Engineering techniques requires the identification and matching of appropriate context models with Web Service models. In this paper, a new ongoing research direction is presented, which refers to model transformation for allowing the identification of appropriate context sources and ensuring their compatibility with Web Services. Matchmaking principles between Web Service and context models are examined in order to extract a reasoning mechanism on context adaptation compatibility. In specific, the principles of graph transformation are mainly exploited.

The increasing popularity of Web services for application integration has strengthened the need for automated Web service composition and joint execution. A lot of attention has been paid recently towards techniques for creating a composite Web service from individual Web services based on user requirements, and driven by a variety of criteria. However, the major lacuna so far in Web service composition is the lack of a holistic requirements-driven approach for modeling the Web service execution lifecycle. In this paper we present such an approach based on our earlier work on context-driven Web service modeling. In particular, we separate requirements into two parts - functional and extrafunctional requirements (FRs and EFRs, respectively). We express FRs as commitments made by individual Web ser-vices towards the composite Web service, and EFRs as rules that constrain the behavior of the individual Web services while they execute against their FRs. We also present a conceptual model that can be used for tracking requirements during Web service execution.

Standardized web services technology has been used in the construction industry to support activities such as sensing data integration, supply chain collaboration, and performance monitoring. Currently these web services are used for exchanging messages with simple structure and small size. However, building information models often contain rich information and are huge in size. Therefore, retrieving and exchanging building information models using standardized web services technology is challenging. This paper discusses the usage of ontologies and context awareness in standardized web services technology to facilitate efficient and lightweight information retrieval and exchange. Ontologies for building information such as Industry Foundation Classes (IFC) and aecXML have been developed for over a decade and become mature. These ontologies can be leveraged to structure the input and output messages of web services. On the other hand, context awareness not only provides data security according to user’s location, time, and profile, but also enables retrieval and exchange of partial information models. This paper presents and demonstrates an ontology-based context aware web service framework that is designed for retrieval and updating of building information models.

The recent approaches for Web services composition tend to integrate heterogeneous business processes executed in Peer-to-Peer networks. In such networks, component Web services are invoked on independent peers and are orchestrated according to the transactional requirements defined by the designers or the users of the composite Web service. Since component Web services can be dynamically invoked and are generally implemented as black boxes, concurrency between them may appear. This paper presents the transactional execution model of composite Web services exploiting the transactional properties of their component Web services. The proposed concurrency control is ensured by a decentralized serialization graph based on an optimistic protocol and on the hierarchical structure of the composition. The globally correct execution of the composite Web service is achieved by communication among dependent subtrans-actions and the peers they have accessed.

The automatic composition of Web services requires the existing services to be encoded in a semantic form, such as ontology. If Web services are represented with ontology, we can automatic compose Web services by means of their semantics. Ontology modeling is divided into two steps: input/output parameters modeling and Web services modeling. First, we collect Web services' input/output parameters, represent them with classes in ontology, and transform Web services to properties in ontology, define relations between classes and properties. Then we judge Web services' relations based on relations between properties transformed from these Web services and estimate whether these Web services can be composed.

Context-aware Web service would significantly benefit the interactions between human, applications, and the environment.

Context-aware Web services are identified as an important technology to support new applications on the future Internet. Context information has several qualities that make the development of these services challenging, compared to conventional, Web services. Therefore, sound software engineering practices are needed during their development and execution. This article discusses a novel software engineering-based approach, which leverages the benefits of model-driven architecture, aspect-oriented modeling, and formal model checking, for modeling and verifying context-aware services. The approach is explored using a real-world case study in intelligent transport. An evaluation framework is established to validate the main methods and tools employed.

Users of Web and grid services often must temporarily delegate some or all of their rights to a software entity to perform actions on their behalf. The problem with the typical grid services approach (X. 509 proxy certificates) is that commercial Web services tooling fails to recognize these certificates or process them properly. The security assertion markup language (SAML) is a standardized XML-based framework for exchanging authentication, authorization and attribute information. SAML has broadening commercial support but lacks delegation capabilities. To address this shortcoming, we exploit SAML's inherent extensibility to create a delegation framework for Web and grid services that supports both direct and indirect delegation. We develop a set of verification rules for delegation tokens that rely on WS-Security X.509 signatures, but do not force any trust relationship between the delegatee and the target service. We have implemented the framework on two common Web service hosting environments: Java/Tomcat and .NET. By leveraging existing Web services standards, we make it easier for Grid practitioners to build and consume Web and grid services without resorting to grid-specific protocols.

Preface. 1. Introduction. 1.1 What is COP? 1.2 Why is COP important? 1.3 What is a component? 1.4 Hardware components and software components. 1.5 From OOP to COP. 1.6 Component-based software engineering. 1.7 Summary. 1.8 Self-review questions. 1.9 Exercises. 2. A Theory of Components. 2.1 Principles of COP. 2.2 Infrastructures of COP. 2.3 Component models. 2.4 Connection models. 2.5 Deployment models. 2.6 Unifying component technologies. 2.7 Summary. 2.8 Self-review questions. 2.9 Exercises. 3. COP with JavaBeans. 3.1 Overview of JavaBeans technology. 3.2 The component model of JavaBeans. 3.3 The connection model of JavaBeans. 3.4 The deployment model of JavaBeans. 3.5 Examples and lab practice. 3.6 Summary. 3.7 Self-review questions. 3.8 Exercises. 4. Enterprise JavaBeans Components. 4.1 The EJB a rchitecture. 4.2 The component model of EJB. 4.3 The connection model of EJB. 4.4 The deployment model of EJB. 4.5 Examples and lab practice. 4.6 Summary. 4.7 Self-review questions. 4.8 Exercises. 4.9 Programming exercises. 5. CORBA Components. 5.1 The COBRA component infrastructure. 5.2 The CORBA component model (CCM). 5.3 The connection model of CORBA and CCM. 5.4 The deployment model of CORBA and CCM. 5.5 Examples and lab practice. 5.6 Summary. 5.7 Self-review questions. 5.8 Exercises. 5.9 Programming exercises. 6. .NET Components. 6.1 The .NET framework. 6.2 The component model of .NET. 6.3 The connection model of .NET. 6.4 .NET component deployments. 6.5 Visual Studio .NET. 6.6 Examples and lab practice. 6.7 Summary. 6.8 Self-review questions. 6.9 Exercises. 6.10 Programming exercises. 7. COP with OSGi Components. 7.1 Overview of OSGi technology. 7.2 The component model of OSGi. 7.3 The connection model of OSGi. 7.4 The deployment model of OSGi. 7.5 Examples and lab practice. 7.6 Summary. 7.7 Self-review questions. 7.8 Exercises. 8. Web Services Components. 8.1 The Web Services framework. 8.2 The component model of Web Services. 8.3 The connection model of Web Services. 8.4 Web Services component deployment. 8.5 Examples and lab practice. 8.6 Summary. 8.7 Self-review questions. 8.8 Exercises. 8.9 Programming exercises. Appendix.

Web services form the core of e-business and hence, have experienced a rapid development in the past few years. This has led to a demand for a discovery mechanism for Web services. Discovery is the most important task in the Web service model because Web services are useless if they cannot be discovered. A large number of Web service discovery systems have been developed. Universal Description, Discovery and Integration (UDDI) is a typical mechanism that stores indexes to Web services but it does not support semantics. Semantic Web service discovery systems that have been developed include systems that support matching Web services using the same ontology, systems that support matching Web services using different ontologies, and systems that support limitations of UDDI. This paper presents a survey of Web service discovery systems, focusing on systems that support semantics. The paper also elaborates on open issues relating to such discovery systems. Request access from your librarian to read this chapter's full text.

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.

While Web service models become increasingly popular and many service providers start to offer all kinds of Web services, the quality of service (QoS) for Web services has become an important factor for service requesters to consider during the selection process of appropriate Web services. In this paper, we present an evaluation and selection framework (CosmosQoS) for QoS-required Web services. A novel architecture and reputation appraisal model to monitor, store and evaluate the physical usage and post-condition of requested Web services in a requester-located network is proposed to better support service requesters such that they can select suitable Web services based on their QoS requirements, trustworthiness of Web services, and effect of network connection and configuration between service requesters and providers.

Web services form the core of e-business and hence, have experienced a rapid development in the past few years. This has led to a demand for a discovery mechanism for web services. Discovery is the most important task in the web service model because web services are useless if they cannot be discovered. A large number of web service discovery systems have been developed. Universal Description, Discovery and Integration (UDDI) is a typical mechanism that stores indexes to web services but it does not support semantics. Semantic web service discovery systems that have been developed include systems that support matching web services using the same ontology, systems that support matching web services using different ontologies, and systems that support limitations of UDDI. This paper presents a survey of web service discovery systems, focusing on systems that support semantics. The paper also elaborates on open issues relating to such discovery systems.