Vuong Xuan Tran

A new QoS ontology and its QoS-based ranking algorithm for Web services

Abstract Web service composition is a promising solution for building distributed applications on the Internet in which Web service discovery is a key step. With a number of Web services having similar functionality, it is necessary to rank those services to select the best Web services for a request. QoS information which can reflect user’s expectation and experience of using a service is often used as a distinguish factor in a service ranking algorithm. Different service providers and participants may use different QoS concepts for describing service quality information. Therefore, it leads to the issue of semantic interoperability of QoS. In this paper, we propose a novel approach for designing and developing a QoS ontology and its QoS-based ranking algorithm for evaluating Web services. The QoS ontology can support not only describing QoS information in great detail but also facilitating various service participants expressing their QoS offers and demands at different levels of expectation. The QoS-based ranking algorithm adopted Analytic Hierarchy Process (AHP), a multiple criteria decision making technique, as an underlying mechanism for developing a flexible and dynamic ranking algorithm. The proposed QoS ontology and ranking algorithm can be used in various applications in order to facilitate automatic and dynamic discovery and selection of Web services.

OWL-T: A Task Ontology Language for Automatic Service Composition

In order to satisfy incremental business demands, it is often required to combine functionalities of several services together. A number of approaches for service composition have been therefore proposed in both academic and industrial communities. These approaches, such as BPEL, WSCI, etc. can be categorized into static, manual service composition methods. In addition, by applying Semantic Web technologies, many research works have been investigated to support automatic service composition. Despite of the significant results being achieved, the task of service composition is still a challenging and complex issue. The main reason is that the former approaches require too much detail and technical interventions for defining business processes while the latter approaches are not much scalable for sophisticated applications. In this paper, we will introduce our approach for developing an ontology/language based on the OWL, called OWL-T (T stands for task), which can be used for users describing and specifying formally and semantically their needs at a high-level abstraction, which can be then transformed into executable business processes by underlying systems. The OWL-T aims at facilitating the modeling of complex demands or systems without regarding details of low-level and technical aspects of underlying infrastructure.

A Survey and Analysis on Semantics in QoS for Web Services

When a number of Web services are deployed there may be many Web services can provide expected functions of a service request. QoS can be then used to distinguish those similar functional services in order to select the best services in terms of their quality. Various QoS models and QoS languages have been proposed for Web services. Therefore different organizations and companies may adopt different QoS models for expressing quality of provided Web services. This leads to the issue of interoperability of QoS meaning between and among service participants which join in service cooperation. Semantic technology has been applied in recent works aiming at providing an efficient and compatible method for describing and reasoning about QoS of different systems. In this paper, we present an overview of prominent research works related to developing QoS ontologies and discuss their advantages and shortcomings. Basing on such analysis, we indicate open issues that need further investigation in ongoing works aiming at developing and using QoS ontologies for Web service discovery, management, and composition.

WS-QoSOnto: A QoS Ontology for Web Services

Web service discovery is one important step in Web service composition. As more and more Web services are available, it is necessary to distinguish and rank Web services which have similar functionality. QoS information has substantial impacts on user¿s expectation and experience of using a Web service. Therefore QoS is often used as a main factor to distinguish quality of Web services. A number of QoS languages and models have been proposed. And different service providers and participants may use different QoS concepts and measurement methods for describing service quality information. This leads to the issue of QoS semantic interoperability. In this paper, we propose a novel approach for designing and building a QoS ontology for Web services. The ontology can support not only describing QoS information in great detail but also facilitating various service participants expressing their QoS offers and demands at different levels of expectation.

A new service matching definition and algorithm with SAWSDL

Semantic Web service (or briefly “SWS”) matching is a potential solution for automatic service discovery in various applications such as dynamic and automatic Web service composition. A number of approaches for SWS matching have been proposed. Most of them solely relied on concept subsumption relationship to improve the precision of Web service matching result from lexical-based methods. However such approaches suffer from several limitations such as not providing a fine-grained service matching degree, not supporting many-to-many matching between operation parameters, and not deriving data mappings between them. In this paper, we introduce a novel method for SWS matching based on SAWSDL, a semantic annotation specification for WSDL. We first define a fine-grained service matching result and then develop a corresponding service matching algorithm which can facilitate many-to-many matching of operation parameters as well as deriving concrete data mappings between them. Semantic techniques are used to infer and match data elements of operation parameters between a request and a service. The proposed algorithm was implemented and applied in the SeTEF — an automatic task-oriented business process execution system.

OWL-T: An Ontology-based Task Template Language for Modeling Business Processes

With the growth of business demands, it becomes crucial to compose existing services in order to create new value added applications. Some languages like BPEL, WSCI enable creating complex composite services but they only allow static, manual composition. Basing on semantic technologies, many researchers have proposed (semi-)automatic methods for service composition, which often rely on a close world assumption and are not scalable for complex systems. In essence, these approaches lack a means for users expressing their complex business demands in a form that facilitates systems automatically generating a composite service. In this paper, we introduce our approach to provide an ontology/language based on the OWL, called OWL-T, for formally and semantically defining task templates that capture business demands at a high-level abstraction. Therefore, with a complex business demand expressed in terms of structured tasks, users need not to care about technical details of composition languages and an automatic composition method can be used to transform task templates into executable processes. In addition, based on semantic technologies, the OWL-T ontology also enhances the interoperability for better sharing and reuse of task templates in various domains of discourse.

Using semantic technologies for dynamic and flexible trip planning

Travel and tourism are potential areas for applying Web service technologies, especially with service integration of multiple travel information sources and tasks. It is required to support users dynamically and flexibly planning their trip plans which can be realized by various services. In this paper, we present a semantic method that automatically transforms high level trip plan templates into executable processes. A trip plan is defined by using OWL-T, a task ontology language, to capture users’ travel requirements. Semantic technologies are used to map such trip templates into executable processes expressed in BPEL, a business process language. A prototype system was developed for illustration.

A Task-Oriented Framework for Automatic Service Composition

Syntactic composition languages like BPEL, WSCI are insufficient for end users because of many technical details. In order to reduce the complexity of service composition, various approaches based on semantic technologies and planning techniques have been developed for automatic service composition. However these approaches have focused on composition aspects and have not facilitated users expressing their business demands easily and flexibly. In this paper, we propose a semantic framework that automatically transforms high level task definitions into executable processes. The task language OWL-T is developed for defining complex tasks that capture users’ business requirements. Semantic technologies are utilized to map such task templates into executable processes expressed in the BPEL language. An implemented prototype was developed for illustrating the practical potential of the framework.

Explaining Answers from Agent Communication of Semantic Web Information

In semantic Web, an application can not only provide explicit information but also infer implicit knowledge. Besides, an answer can be also derived from multiple sources and by multiple agents. In order to trust and use such an answer, a user needs a proof and/or explanations of that answer, which contain information related to knowledge sources, systems, reasoning methods, relationships of data items, etc. In this paper, we extend our existing logical agent framework so that agents can not just reason with multiple distributed ontologies but also record proofs and provide explanations of their answers. A proof contains essential information related to a reasoning process including agents, sources of ontologies, rules, facts, etc. Then various explanations can be then generated from a proof for users, depending on their purpose and requirement. Agents are capable of creating, exchanging, and accumulating (sub-) answers along with their proofs and explanations among each other when they cooperate in solving common problems.

Proof for Multi-agent Communication of Semantic Web Information

In semantic Web, an application should not just giving a correct answer but also providing a proof or some kinds of explanations for that answer. A proof contains information related to the process that creates an answer like knowledge sources, reasoning systems, etc. Provided a proof or explanations, a user can trust and use a result with confidence. Such a means of answer provenance is even more important for distributed systems where an answer may be derived from many knowledge sources and by several systems. In this paper, basing on our existing logical framework for multi-agent communication of semantic Web information, we extend the framework so that the agents are capable of tracing and providing proofs of their answers. A proof contains information about sources of knowledge, agents participated in the reasoning process as well as facts, rules, and axioms that are employed for inferring an answer. Such proofs are essential for various tasks like checking and validating answers, computing trust information, or generating explanations of answers.