Publications in Service Discovery

Articles in Refereed Journals:

1. 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.

2. Shuping Ran. A model for web services discovery with QoS. SIGecom Exch., Vol. 4, Num. 1, pages 1-10, ACM, 2003.
   Abstract: Web services technology has generated a lot interest, but its adoption rate has been slow. This paper discusses issues related to this slow take up and argues that quality of services is one of the contributing factors. The paper proposes a new Web services discovery model in which the functional and non-functional requirements (i.e. quality of services) are taken into account for the service discovery. The proposed model should give Web services consumers some confidence about the quality of service of the discovered Web services.

Articles in Refereed Conferences:

1. Kyriakos Kritikos, Dimitris Plexousakis. Evaluation of QoS-Based Web Service Matchmaking Algorithms. International Conference on Services Computing, 2008.
   Abstract: Web Service (WS) discovery is a prerequisite for achieving WS composition and orchestration. Although a lot of esearch has been conducted on the functional discovery of WSs, the proposed techniques fall short when faced with the foreseen increase in the number of (potentially functionally- equivalent) WSs. The above situation can be resolved with the addition of non-functional (Quality of Service (QoS)) discovery mechanisms to WS discovery engines. QoS-based WS matchmaking algorithms have been devised for this reason. However, they are either slow - as they are based on ontology reasoners - or produce inaccurate results. Inaccuracy is caused both by the syntactic matching of QoS concepts and by wrong matchmaking metrics. In this paper, we present two Constraint Programming (CP) QoS-based WS discovery algorithms for unary constrained WS specifications that produce accurate results with good performance. We also evaluate these algorithms on matchmaking time, precision and recall in different settings in order to demonstrate their efficiency and accuracy.

2. Kyriakos Kritikos, Dimitris Plexousakis. OWL-Q for Semantic QoS-based Web Service Description and Discovery. First International Joint Workshop on Service Matchmaking and Resource Retrieval in the Semantic Web, November 2007.
   Abstract: Semantic Web Services are emerging for their promise to produce a more accurate and precise Web Service discovery process. However, most of research approaches focus only on the functional part of semantic Web Service description. The above fact along with the proliferation of Web Services is highly probable to lead to a situation where Web Service registries will return many functionally-equivalent Web Service advertisements for each user request. This problem can be solved with the semantic description of QoS for Web Services. QoS is a set of non-functional properties encompassing performance and network- related characteristics of resources. So it can be used for distinguishing between functionally-equivalent Web Services. Current research approaches for QoS-based Web Service description are either syntactic or poor or non-extensible. To solve this problem, we have developed a rich and extensible ontological specification called OWL-Q for semantic QoS-based Web Service description. We analyze all OWL-Q parts and reason that rules should be added in order to support property inferencing and constraint enforcement. Finally, we line out our under-development semantic framework for QoS-based Web Service description and discovery.

3. Ester Giallonardo, Eugenio Zimeo. More Semantics in QoS Matching. SOCA, pages 163-171, 2007.
   Abstract: The evolution of the Web towards a global computing environment is promoting new research efforts aimed at the formal characterization of Web Services QoS. Reasoning on QoS is a key to improve matching process during the discovery of desired services and a step towards the transformation of applications in collections of loosely coupled services virtually connected by semantic similarities. The paper presents the on QoS ontology, an openly available OWL ontology for QoS, and evaluates it in a QoS-aware matching environment. The ontology can be used to express functions of QoS metrics useful to improve the recall tied to the matching of a template request with target Web Services. To this end, the ontology introduces the concept of derivation in the matching process. This gives the possibility of matching a QoS template with published Web Services by deriving different QoS parameters when a one-to-one matching fails. The proposed matching algorithm utilizes a reasoner that exploits the ontology to avoid apparent mismatches. An experimental evaluation shows that exploiting QoS knowledge significantly improves matching recall without deteriorating precision.

4. Kyriakos Kritikos, Dimitris Plexousakis. Requirements for QoS-based Web Service Description and Discovery. COMPSAC (2), pages 467-472, 2007.
   Abstract: The goal of Service Oriented Architectures is to enable the creation of business applications through the automatic discovery and composition of independently developed and deployed (Web) services. Automatic discovery of Web Services (WSs) can be achieved by incorporating semantics into a richer WS description model (WSDM) and the use of Semantic Web (SW) technologies in the WS matchmaking and selection models. A sufficiently rich WSDM should encompass not only functional but also non-functional aspects like Quality of Service (QoS). QoS is a set of performance attributes that has a substantial impact on WS requesters' expectations. Thus, it can be used as a discriminating factor of functionally-equivalent WSs. The focus of this paper is twofold: to analyze the requirements of a semantically rich QoS-based WSDM and to provide SW and constrainedbased mechanisms for enriching syntactic QoS-based WS Discovery (WSDi) algorithms. In addition, a roadmap of extending WS standard techniques for realizing semantic, functional and QoS-based WSDi is presented.

5. Kyriakos Kritikos, Dimitris Plexousakis. Semantic QoS-based Web Service Discovery Algorithms. Fifth European Conference on Web Services, pages 181-190, IEEE Computer Society, 2007.
   Abstract: The success of the Web Service (WS) paradigm has led to a proliferation of available WSs, which are advertised in WS registries. While sophisticated semantic WS discovery algorithms are operating on these registries to return matchmaking results with high precision and recall, many functionally-equivalent WSs are returned. The solution to the above problem comes in terms of semantic QoS-based description and discovery of WSs. We have already presented a rich and extensible ontology language for QoS-based WS description called OWL-Q. We have also proposed a semantic QoS metric matching algorithm. Based on this algorithm, we have extended a CSP-based approach for QoS-based WS discovery. In this paper, we firstly analyze the evolution of OWL-Q and its extension with SWRL rules, we propose a modification to the metric matching algorithm and we show the way the metric alignment process takes place. Then we propose two novel semantic QoS-based WS Discovery algorithms that return matches even for over-constrained QoS-based WS requests. The first one deals with unary constraints while the second one is more generic. Finally, implementation aspects of our QoS-based WS discovery system are discussed.

6. Kyriakos Kritikos, Dimitris Plexousakis. Semantic QoS Metric Matching. ECOWS, pages 265-274, 2006.
   Abstract: As the Web Service paradigm gains popularity for its promise to transform the way business is conducted, the number of deployed Web Services grows with a fast rate. While sophisticated semantic discovery mechanisms have been invented to overcome the UDDI's syntactic discovery solution in order to provide more recallable and precise results, the amount of functionally equivalent Web Services returned is still large. The solution to this problem is the description of the QoS non-functional aspect of Web Services. QoS encompasses the performance of Web Services and can be used as a discriminator factor for refining Web Service advertisement result lists. However, most scientific efforts presented so far are purely syntactic and are not capturing all aspects of QoS-based Web Service description leading to imprecise syntactic discovery mechanisms. This paper presents a novel, rich and extensible ontology-based approach for describing QoS of Web Services that complements OWL-S. It is shown that, by using this approach and by introducing the concept of semantic QoS metric matching, QoS-based syntactic matchmaking and selection algorithms are transformed to semantic ones leading to better results.

7. Vikas Deora, Jianhua Shao, Gareth Shercliff, Patrick J. Stockreisser, W. A. Gray, N. J. Fiddian. Incorporating QoS Specifications in Service Discovery. WISE Workshops, pages 252-263, 2004.
   Abstract: In this paper, we extend the current approaches to service discovery in a service oriented computing environment, such as Web Services and Grid, by allowing service providers and consumers to express their promises and requirements for quality of service (QoS). More specifically, we allow service providers to advertise their services in an extended DAML-S that supports quality specifications, and we allow service consumers to request services by stating required quality levels. We propose a model here for incorporating QoS specifications and requirements in service discovery, and describe how matchmaking between advertised and requested services based on functional as well as quality requirements is supported in our model.

8. Gwen Salaün, Lucas Bordeaux, Marco Schaerf. Describing and Reasoning on Web Services using Process Algebra. ICWS, 2004.
   Abstract: We argue that essential facets of web services, and especially those useful to understand their interaction, can be described using process-algebraic notations. Web service description and execution languages such as BPEL are essentially process description languages; they are based on primitives for behaviour description and message exchange which can also be found in more abstract process algebras. One legitimate question is therefore whether the formal approach and the sophisticated tools introduced for process algebra can be used to improve the effectiveness and the reliability of web service development. Our investigations suggest a positive answer, and we claim that process algebras provide a very complete and satisfactory assistance to the whole process of web service development. We show on a case study that readily available tools based on process algebra are effective at verifying that web services conform their requirements and respect properties. We advocate their use both at the design stage and for reverse engineering issues. More prospectively, we discuss how they can be helpful to tackle choreography issues.

9. Vladimir Tosic, Kruti Patel, Bernard Pagurek. WSOL - Web Service Offerings Language. CAiSE '02/ WES '02: Revised Papers from the International Workshop on Web Services, E-Business, and the Semantic Web, pages 57-67, Springer-Verlag, 2002.
   Abstract: WSOL (Web Service Offerings Language) is an XML (Extensible Markup Language) notation compatible with the WSDL (Web Services Description Language) standard. While WSDL is used for describing operations provided by Web Services, WSOL enables formal specification of multiple classes of service for one Web Service. A service offering is a formal representation of one class of service for a Web Service. As classes of service for Web Services are determined by combinations of various constraints, WSOL enables formal specification of functional constraints, some QoS (a.k.a., non-functional) constraints, simple access rights (for differentiation of service), price, and relationships with other service offerings of the same Web Service. Describing a Web Service in WSOL, in addition to WSDL, enables selection of a more appropriate Web Service and service offering for particular circumstances. Further, it supports dynamic adaptation and management of Web Service compositions using manipulation of service offerings.