Publications in 2005

Articles in Refereed Journals:

1. Groenmo, R., Jaeger, M.C.. Model-driven semantic Web service composition. Software Engineering Conference, 2005. APSEC '05. 12th Asia-Pacific, To Appear, December 2005.
   Abstract: As the number of available Web services increases there is a growing demand to realise complex business processes by combining and reusing available Web services. The reuse and combination of services results in a composition of Web services that may also involve services provided in the Internet. With semantically described Web services, an automated matchmaking of capabilities can help identify suitable services. To address the need for semantically defined Web services, OWL-S and WSML have been proposed as competing semantic Web service languages. We show how the proposed semantic Web service languages can be utilized within a model-driven methodology for building composite Web services. In addition we combine the semantic-based discovery with the support for processing QoS requirements to apply a ranking or a selection of the candidates. The methodology describes a process which guides the developer through four phases, starting with the initial modelling, and ending with a new composite service that can be deployed and published to be consumed by other users.

2. Ma, K.J.. Web services: what's real and what's not?. IT Professional, Vol. 7, Num. 2, pages 14-21, March 2005.
   Abstract: The idea of abstracted, well-defined, and ubiquitously invokable services replacing proprietary interprocess communications has been a goal of system designers for a long time. The rise of Web services has led to a lot of misconceptions about how they can and cannot support the holy grail of a service-oriented architecture (SOA). This article seeks to put Web services in perspective, explaining their current capabilities and what industry can expect from them in the near term. It gives an overview of how technologies such as the Extensible Markup Language (XML), XML schemas, Extensible Stylesheet Language Transformations (XSLT), the Simple Object Access Protocol (SOAP), the Web Services Description Language (WSDL), and universal description, discovery, and integration (UDDI) fit into the equation for an SOA.

3. Wil M. P. van der Aalst. Business alignment: using process mining as a tool for Delta analysis and conformance testing. Requir. Eng., Vol. 10, Num. 3, pages 198-211, 2005.
   Abstract: Increasingly, business processes are being controlled and/or monitored by information systems. As a result, many business processes leave their "footprints" in transactional information systems, i.e., business events are recorded in so-called event logs. Process mining aims at improving this by providing techniques and tools for discovering process, control, data, organizational, and social structures from event logs, i.e., the basic idea of process mining is to diagnose business processes by mining event logs for knowledge. In this paper we focus on the potential use of process mining for measuring business alignment, i.e., comparing the real behavior of an information system or its users with the intended or expected behavior. We identify two ways to create and/or maintain the fit between business processes and supporting information systems: Delta analysis and conformance testing. Delta analysis compares the discovered model (i.e., an abstraction derived from the actual process) with some predefined processes model (e.g., the workflow model or reference model used to configure the system). Conformance testing attempts to quantify the "fit" between the event log and some predefined processes model. In this paper, we show that Delta analysis and conformance testing can be used to analyze business alignment as long as the actual events are logged and users have some control over the process.

4. Schahram Dustdar, Wolfgang Schreiner. A survey on web services composition. IJWGS, Vol. 1, Num. 1, pages 1-30, 2005.
   Abstract: Due to the web services' heterogeneous nature, which stems from the definition of several XML-based standards to overcome platform and language dependence, web services have become an emerging and promising technology to design and build complex inter-enterprise business applications out of single web-based software components. To establish the existence of a global component market, in order to enforce extensive software reuse, service composition experienced increasing interest in doing a lot of research effort. This paper discusses the urgent need for service composition, the required technologies to perform service composition. It also presents several different composition strategies, based on some currently existing composition platforms and frameworks, re-presenting first implementations of state-of the-art technologies, and gives an outlook to essential future research work.

5. Papazoglou, M.P., van den Heuvel, W.-J.. Web services management: a survey. Internet Computing, IEEE, Vol. 9, Num. 6, pages 58-64, November/December 2005.
   Abstract: Solutions based on service-oriented architectures are promising in that they leverage common services and enable collaborative business processes that cross organizational boundaries. However, because Web services applications can span multiple hosts, operating systems, languages, and enterprises, it's problematic to measure, control, and manage application availability and performance. In addition to discussing the relationship of Web services management to traditional distributed systems management, this survey explores various Web services management approaches and their underlying architectural concepts.

6. James Pasley. How BPEL and SOA Are Changing Web Services Development. IEEE Internet Computing, Vol. 9, Num. 3, pages 60-67, 2005.
   Abstract: As the use of Web services grows, organizations are increasingly choosing the Business Process Execution Language for modeling business processes within the Web services architecture. In addition to orchestrating organizations' Web services, BPEL's strengths include asynchronous message handling, reliability, and recovery. By developing Web services with BPEL in mind, organizations can implement aspects of the service-oriented architecture that might previously have been difficult to achieve.

7. Tao Yu, Kwei-Jay Lin. Service selection algorithms for Web services with end-to-end QoS constraints. Inf. Syst. E-Business Management, Vol. 3, Num. 2, pages 103-126, 2005.
   Abstract: Web services are new forms of Internet software that can be universally deployed and invoked using standard protocols. Services from different providers can be integrated into a composite service regardless of their locations, platforms, and/or execution speeds to implement complex business processes and transactions. In this paper, we study the end-to-end QoS issues of composite services by utilizing a QoS broker that is responsible for selecting and coordinating the individual service component. We design the service selection algorithms used by QoS brokers to construct the optimal composite service. The objective of the algorithms is to maximize the user-defined utility function value while meeting the end-to-end delay constraint. We propose two solution approaches to the service selection problem: the combinatorial approach, by modeling the problem as the Multiple Choice Knapsack Problem (MCKP), and the graph approach, by modeling the problem as the constrained shortest path problem in the graph theory. We study efficient solutions for each approach.

Articles in Refereed Conferences:

1. Huang, H., Tsai, W.-T., Paul, R.. Automated model checking and testing for composite Web services. pages 300-307, May 2005.
   Abstract: Web services form a new distributed computing paradigm. Collaborative verification and validation are important when Web services from different vendors are integrated together to carry out a coherent task. This paper presents a new approach to verify Web services by model checking the process model of OWL-S (Web ontology language for Web services) and to validate them by the test cases automatically generated in the model checking process. We extend the BLAST, a model checker that handles control flow model naturally, to handle the concurrency in OWL-S. We also propose enhancement in OWL-S and PDDL (Planning Domain Definition Language) to facilitate the automated test case generation. Experiments on realistic examples are provided to illustrate the process.

2. Rocco De Nicola, Gianluigi Ferrari, Ugo Montanari, Rosario Pugliese, Emilio Tuosto. A Basic Calculus for Modelling Service Level Agreements. International Conference on Coordination Models and Languages, LNCS, Vol. 3454, pages 33-48, Springer Verlag, April 2005.
   Abstract: The definition of suitable abstractions and models for identifying, understanding and managing Quality of Service (QoS) constraints is a challenging issue of the Service Oriented Computing paradigm. In this paper we introduce a process calculus where QoS attributes are first class objects. We identify a minimal set of primitives that allow capturing in an abstract way the ability to control and coordinate services in presence of QoS constraints.

3. Bernd-Holger Schlingloff, Axel Martens, Karsten Schmidt. Modeling and Model Checking Web Services. Vol. 126, pages 3-26, Elsevier, March 2005.
   Abstract: We give an overview on web services and the web service technology stack. We then show how to build Petri net models of web services formulated in the specification language BPEL4WS. We define an abstract correctness criterion for these models and study the automated verification according to this criterion. Finally, we relate correctness of web service models to the model checking problem for alternating temporal logics.

4. Luciano Baresi, Sam Guinea. Towards Dynamic Monitoring of WS-BPEL Processes. ICSOC, pages 269-282, 2005.
   Abstract: The intrinsic flexibility and dynamism of service-centric applications preclude their pre-release validation and demand for suitable probes to monitor their behavior at run-time. Probes must be suitably activated and deactivated according to the context in which the application is executed, but also according to the confidence we get on its quality. The paper supports the idea that significant data may come from very different sources and probes must be able to accommodate all of them. The paper presents: (1) an approach to specify monitoring directives, called monitoring rules, and weave them dynamically into the process they belong to; (2) a proxy-based solution to support the dynamic selection and execution of monitoring rules at run-time; (3) a user-oriented language to integrate data acquisition and analysis into monitoring rules.

5. Alistair P. Barros, Marlon Dumas, Arthur H. M. ter Hofstede. Service Interaction Patterns. Business Process Management, pages 302-318, 2005.
   Abstract: With increased sophistication and standardization of modeling languages and execution platforms supporting business process management (BPM) across traditional boundaries, has come the need for consolidated insights into their exploitation from a business perspective. Key technology developments in BPM bear this out, with several web services-related initiatives investing significant effort in the collection of compelling use cases to heighten the exploitation of BPM in multi-party collaborative environments. In this setting, we present a collection of patterns of service interactions which allow emerging web services functionality, especially that pertaining to choreography and orchestration, to be benchmarked against abstracted forms of representative scenarios. Beyond bilateral interactions, these patterns cover multilateral, competing, atomic and causally related interactions. Issues related to the implementation of these patterns using established and emerging web services standards, most notably BPEL, are discussed.

6. Aysu Betin-Can, Tevfik Bultan, Xiang Fu. Design for verification for asynchronously communicating Web services. WWW, pages 750-759, 2005.
   Abstract: We present a design for verification approach to developing reliable web services. We focus on composite web services which consist of asynchronously communicating peers. Our goal is to automatically verify properties of interactions among such peers. We propose a design pattern that eases the development of such web services and enables a modular, assume-guarantee style verification strategy. In the proposed design pattern, each peer is associated with a behavioral interface description which specifies how that peer will interact with other peers. Using these peer interfaces we automatically generate BPEL specifications to publish for interoperability. Assuming that the participating peers behave according to their interfaces, we verify safety and liveness properties about the global behavior of the composite web service during behavior verification. During interface verification, we check that each peer implementation conforms to its interface. Using the modularity in the proposed design pattern, we are able to perform the interface verification of each peer and the behavior verification as separate steps. Our experiments show that, using this modular approach, one can automatically and efficiently verify web service implementations.

7. Gerardo Canfora, Massimiliano Di Penta, Raffaele Esposito, Maria Luisa Villani. An approach for QoS-aware service composition based on genetic algorithms. GECCO '05: Proceedings of the 2005 conference on Genetic and evolutionary computation, pages 1069-1075, ACM, 2005.
   Abstract: Web services are rapidly changing the landscape of software engineering. One of the most interesting challenges introduced by web services is represented by Quality Of Service (QoS)-aware composition and late-binding. This allows to bind, at run-time, a service-oriented system with a set of services that, among those providing the required features, meet some non-functional constraints, and optimize criteria such as the overall cost or response time. In other words, QoS-aware composition can be modeled as an optimization problem.We propose to adopt Genetic Algorithms to this aim. Genetic Algorithms, while being slower than integer programming, represent a more scalable choice, and are more suitable to handle generic QoS attributes. The paper describes our approach and its applicability, advantages and weaknesses, discussing results of some numerical simulations.

8. Gerardo Canfora, Massimiliano Di Penta, Raffaele Esposito, Maria Luisa Villani. QoS-Aware Replanning of Composite Web Services. ICWS '05: Proceedings of the IEEE International Conference on Web Services, pages 121-129, IEEE Computer Society, 2005.
   Abstract: Run-time service discovery and late-binding constitute some ofthe most challenging issues of service-oriented software engineering.For late-binding to be effective in the case of composite services,a QoS-aware composition mechanism is needed. This meansdetermining the set of services that, once composed, not only willperform the required functionality, but also will best contribute toachieve the level of QoS promised in Service Level Agreements (SLAs). However, QoS-aware composition relies on estimated QoS values and workflow execution paths previously obtained using a monitoring mechanism. At run-time, the actual QoS valuesmay deviate from the estimations, or the execution path may not bethe one foreseen. These changes could increase the risk of breakingSLAs and obtaining a poor QoS. Such a risk could be avoided byreplanning the service bindings of the workflow slice still to be executed. This paper proposes an approach to trigger and perform compositeservice replanning during execution. An evaluation has been performedsimulating execution and replanning on a set of composite serviceworkflows.

9. Jorge Cardoso. About the Data-Flow Complexity of Web Processes. 6th International Workshop on Business Process Modeling, Development, and Support: Business Processes and Support Systems: Design for Flexibility, pages 67-74, 2005.
   Abstract: Abstract. Organizations are increasingly faced with the challenge of managing e-commerce and e-business applications involving Web services and Web processes. In some cases, Web processes’ design can be highly complex, due, for example, to the vast number of services carried out in global markets. High complexity in a process has several undesirable drawbacks, it may result in bad understandability, more errors, defects, and exceptions leading processes to need more time to develop, test, and maintain. Therefore, excessive complexity should be avoided. Flexibility and complexity are guiding principles in the design of business processes. In most business processes, flexibility and complexity are related inversely. Processes with a high complexity tend be less flexible, since it is more complicated to make changes to the process. In our previous work we have defined a metric to measure the control-flow complexity of Web processes. The major goal of this paper is to study the issues and establish the requirements for the development of a metric to analyze the data-flow complexity of Web processes.

10. Samuele Carpineti, Cosimo Laneve, Paolo Milazzo. BoPi - A Distributed Machine for Experimenting Web Services Technologies. ACSD, pages 202-211, 2005.
    Abstract: BoPi is a programming language with a runtime support that allows the distribution and the execution of programs over the network. The language is a process calculus with XML values and datatypes, and with a pattern matching mechanism for deconstructing values. The compiler gives a typesafe bytecode in the form of an XML document, that may be deployed on the network. What comes out is a simple, statically typed, and formally defined core BPEL language with a basic query mechanism supplied by patterns.

11. Rocco De Nicola, Daniele Gorla, Rosario Pugliese. Basic Observables for a Calculus for Global Computing. ICALP, pages 1226-1238, 2005.
    Abstract: We introduce a foundational language for modelling applications over global computers whose interconnection structure can be explicitly manipulated. Together with process distribution, mobility, remote operations and asynchronous communication through distributed data spaces, the language provides constructs for explicitly modelling inter-node connections and for dynamically establishing and removing them. For the proposed language, we define natural notions of extensional observations and study their closure under operational reductions and/or language contexts to obtain barbed congruence and may testing equivalence. For such equivalences, we provide alternative characterizations in terms of a labelled bisimulation and a trace equivalence that can be used for actual proofs.

12. Casey K. Fung, Patrick C. K. Hung, Guijun Wang, Richard C. Linger, Gwendolyn H. Walton. A Study of Service Composition with QoS Management. ICWS, pages 717-724, 2005.
    Abstract: Quality of service (QoS) management in compositions of services requires careful consideration of QoS characteristics of the services and effective QoS management in their execution. A Web service is a software system that supports interoperable application-to-application interaction over the Internet. Web services are based on a set of XML standards such as simple object access protocol (SOAP). The interactions of SOAP messages between Web services form the theoretical model of SOAP message exchange patterns (MEP). Web Services Business Process Execution Language (WSBPEL) defines an interoperable integration model that facilitates automated process integration in intra- and inter-corporate environments. A service-level agreement (SLA) is a formal contract between a Web services requestor and provider guaranteeing quantifiable issues at defined levels only through mutual concessions. Based on a prior research work on message detail record (MDR), this paper further proposes a SOAP message tracking model for supporting QoS end-to-end management in the context of WSBPEL and SLA. This paper motivates the study of QoS management in a Web service composition framework with the evolution of a distributed toolkit in an industrial setting.

13. Dan Hirsch, Emilio Tuosto. SHReQ: Coordinating Application Level QoS. SEFM, pages 425-434, 2005.
    Abstract: We present SHReQ, a formal framework for specifying systems that handle abstract high-level QoS requirements which are becoming more and more important for service oriented computing. SHReQ combines Synchronised Hyperedge Replacement (SHR) with constraint-semirings. SHR is a (hyper)graph rewriting mechanism for modelling evolution of systems. The novelty of the approach relies on the synchronisation mechanism which is based on constraint-semirings, algebraic structures that provide both the mathematics for multi-criteria QoS and the synchronisation policies underlying the SHR mechanism.

14. Hai Huang, Wei-Tek Tsai, Raymond Paul, Yinong Chen. Automated Model Checking and Testing for Composite Web Services.. 8th IEEE International Symposium on Object-Oriented Real-Time Distributed Computing (ISORC 2005), pages 300-307, IEEE Computer Society, 2005.
    Abstract: Web Services form a new distributed computing paradigm. Collaborative verification and validation are important when Web Services from differen vendors are integrated together to carry out a coherent task. This paper presents a new approach to verify Web Services by model checking the proces model of OWL-S (Web Ontology Language for Web Services) and to validate them by the test cases automatically generated in the model checking process. We extend the BLAST, a model checker tha handles control flow model naturally, to handle the concurrency in OWL-S. We also propose enhancement in OWL-S and PDDL (Planning Domain Definition Language) to facilitate the automated test case generation. Experiments on realistic examples are provided to illustrate the process.

15. Michael C. Jaeger, Gero Mühl, Sebastian Golze. QoS-Aware Composition of Web Services: A Look at Selection Algorithms. ICWS, pages 807-808, 2005.
    Abstract: When a composition of Web services is designed, available services are put together to form a defined flow of executions. In a discovery process, a trader proposes available Web services as potential candidates. In a succeeding selection, for each task a trader chooses one candidate to form the optimal composition due to selection criteria. This paper discusses how the selection can consider different quality-of-service (QoS) categories to determine the most suitable candidates for the composition. If more than one category is used for optimisation, a multi-dimensional optimisation problem arises. This mentions similarities to similar combinatorial problems. Then, possible solutions are proposed and their performance is evaluated.

16. Dimka Karastoyanova, Alejandro Houspanossian, Mariano Cilia, Frank Leymann, Alejandro P. Buchmann. Extending BPEL for Run Time Adaptability. EDOC, pages 15-26, 2005.
    Abstract: The existing Web Service Flow (WS-flow) technologies enable both static and dynamic binding of participating Web services (WSs) on the process model level. Adaptability on per-instance basis is not sufficiently supported and therefore must be addressed to improve process flexibility upon changes in the environment. Ad-hoc process instance changes can be enabled by swapping participating WS instances, by modifying port Types of the partners to be invoked, and by changing process logic. In this work we address the problem of dynamic binding of WSs to WS-flow instances at run time, i.e. the ability to exchange a WS instance participating in a WS-flow instance with an alternative one. The problem is additionally complicated by the fact that the execution of a process depends on its deployment. We describe the "find and bind" mechanism, and we show its representation as a BPEL extension. We discuss the benefits that could be gained and the disadvantages it brings in. The mechanism extends and improves the existing process technologies. It facilitates a precisely controlled policy-based selection of WSs at run time and also provides for process instance repair, while maintaining simplicity. We also discuss a prototypical implementation of the presented functionality.

17. Khaled Mahbub, George Spanoudakis. Run-time Monitoring of Requirements for Systems Composed of Web-Services: Initial Implementation and Evaluation Experience. ICWS, pages 257-265, 2005.
    Abstract: This paper describes a framework supporting the runtime monitoring of requirements for systems implemented as compositions of Web-services specified in BPEL. The requirements that can be monitored are specified in event calculus. The paper presents an overview of the framework and describes the architecture and implementation of a tool that we have developed to operationalise it. It also presents the results of a preliminary experimental evaluation of the framework.

18. Mike P. Papazoglou, Paolo Traverso, Schahram Dustdar, Frank Leymann, Bernd J. Krämer. 05462 Service-Oriented Computing: A Research Roadmap. Service Oriented Computing, 2005.
    Abstract: This document presents a Services Research Roadmap that launches four pivotal, inherently related, research themes to Service-Oriented Computing (SOC): service foundations, service composition, service management and monitoring and service-oriented engineering. Each theme is introduced briefly from a technology, state of the art and scientific challenges standpoint. From the technology standpoint a comprehensive review of state of the art, standards, and current research activities in each key area is provided. From the state of the art the major open problems and bottlenecks to progress are identified. During the during seminar each core theme was initially introduced by a leading expert in the field who described the state of the art and highlighting open problems and important research topics for the SOC community to work on in the future. These experts were then asked to coordinate parallel workgroups that were entrusted with an in-depth analysis of the research opportunities and needs in the respective theme. The findings presented in this summary report build on the advice of those panels of experts from industry and academia who participated in this Dagstuhl Seminar and met at other occasions during the past three years, e.g., at the International Conference on Service Oriented Computing (ICSOC, see www.icsoc.org). These experts represent many disciplines including distributed computing, database and information systems, software engineering, computer architectures and middleware and knowledge representation.

19. Florian Rosenberg, Schahram Dustdar. Business Rules Integration in BPEL - A Service-Oriented Approach. CEC, pages 476-479, 2005.
    Abstract: Business rules change quite often. These changes cannot be handled efficiently by representing business rules embedded in the source code of the business logic. Efficient handling of rules that govern ones business is one factor for success. That is where business rules engines play an important role. The service-oriented computing paradigm is becoming more and more popular. Services offered by different providers, are composed to new services by using Web service composition languages such as BPEL. Such process-based composition languages lack the ability to use business rules managed by different business rules engines in the composition process. In this paper, we propose an approach on how to use and integrate business rules in a service-oriented way into BPEL.

20. Wei-Tek Tsai, Yinong Chen, Raymond A. Paul. Specification-Based Verification and Validation of Web Services and Service-Oriented Operating Systems. WORDS, pages 139-147, 2005.
    Abstract: Service-Oriented Architecture (SOA) and Web Services (WS) have received significant attention recently. Even though WS are based on open standards and support software interoperability, but the trustworthy issues of WS has actually limited the growth of WS applications as organizations do not trust those WS developed by other vendors and at the same time they do not have access to the source code. This paper addressed this issue by proposing several solutions including specification-based verification and validation, collaborative testing, and group testing. The key concept is that it is possible to provide a comprehensive evaluation of WS even if their source code is not available.

Publications in Refereed Workshops:

1. S. Nakajima. Model-Checking Behavioral Specification of BPEL Applications. Proceedings of the International Workshop on Web Languages and Formal Methods, WLFM 2005, 2005.
   Abstract: To provide a framework to compose lots of specialised services flexibly, BPEL is proposed to describe Web service flows. Since the Web service flow description is basically a distributed collaboration, writing correct programs in BPEL is not easy. Verifying BPEL program prior to its execution is essential. This paper proposes a method to extract the behavioral specification from a BPEL appliation program and to analyze it by using the SPIN model checker. With the adequate abstraction method and support for DPE, the method can analyze all the four example cases in the BPEL standard document.

Technical Reports and Manuals:

1. Alain Andrieux, Karl Czajkowski, Asit Dan, Kate Keahey, Heiko Ludwig, Toshiyuki Nakata, Jim Pruyne, John Rofrano, Steve Tuecke, Ming Xu. Web Services Agreement Specification (WS-Agreement). Grid Resource Allocation Agreement Protocol, September 2005.
   Abstract: This document describes Web Services Agreement Specification (WS-Agreement), a Web Services protocol for establishing agreement between two parties, such as between a service provider and consumer, using an extensible XML language for specifying the nature of the agreement, and agreement templates to facilitate discovery of compatible agreement parties. The specification consists of three parts which may be used in a composable manner: a schema for specifying an agreement, a schema for specifying an agreement template, and a set of port types and operations for managing agreement life-cycle, including creation, expiration, and monitoring of agreement states.

2. The OASIS Group. Quality Model for Web Services. The Oasis Group, September 2005.
   Abstract: The purpose of this document is to provide a model for Web services quality management and quality factors in the process of developing and using Web services. We define the consistent and systematic conceptual model of Web services quality, which may be used by intimate associates, i.e. stakeholders, developers, service providers, and customers of Web services.

3. The OMG Group. UML$^\mathrm{TM}$ Profile for Modeling Quality of Service and Fault Tolerance Characteristics and Mechanisms. Num. ptc/2005-05-02, The OMG Group, May 2005.

4. I. Foster, H. Kishimoto, A. Savva, D. Berry, A. Djaoui, A. Grimshaw, B. Horn, F. Maciel, F. Siebenlist, R. Subramaniam, J. Treadwell, J. Von Reich . The Open Grid Services Architecture, Version 1.0. ANL, IBM, Fujitsu, NeSC, CCLRC-RAL, UVa, Hitachi, Intel, HP, 2005.
   Abstract: Successful realization of the Open Grid Services Architecture (OGSA) vision of a broadly applicable and adopted framework for distributed system integration, virtualization, and management requires the definition of a core set of interfaces, behaviors, resource models, and bindings. This document, produced by the OGSA working group within the Global Grid Forum (GGF), provides a first version of this OGSA definition. The document focuses on requirements and the scope of important capabilities required to support Grid systems and applications in both e-science and e-business. The capabilities described are Execution Management, Data, Resource Management, Security, Self-Management, and Information. The description of the capabilities is at a high-level and includes, to some extent, the interrelationships between the capabilities.

5. The Oasis Group. Summary of Quality Model for Web Services. The Oasis Group, 2005.