Capability matchmaking of semantic web services with preconditions and effects

In order to solve the problem that the current matchmaking methods for semantic web service mainly focus on the matchmaking of IO （inputs, outputs） descriptions which may result in one-sidedness, a description-logic-based IOPE （inputs, outputs, preconditions, effects） description and matchmaking method is proposed for semantic web service. The description logic concept is used to annotate service IO and the description logic assertion is employed to describe service PE（preconditions, effects）. TBox subsumption checking is used to measure the subsumption relationship between IO descriptions of service request and advertising; ABox consistency checking is used for checking the logical implication between PE descriptions of service request and advertising. Based upon the logical implication, four kinds of PE matching degrees are proposed to measure and compare the pros and cons of the results of matchmaking. They are the exact, perfect, side-effect and common match. Experiments show that the method has a higher precision rate under the same recall rate compared with the existing method.

Pre-filtering based automatic composition of multi-QoS semantic web services

To support the rapid automatic services composition and fulfill multi-quality of service （multi- QoS） demand, we propose a novel approach to realize services composition automatically by a prefihering process. Aimed at a set of web services with similar functionality and different quality of service （QoS） , a semantic services chain is given and a corresponding constructing algorithm is proposed to construct the data structure. A pre-filtering process is put forward to find whether a composition service before planning exists. It can avoid aborted planning. An optimal planning algorithm is proposed which can choose the most suitable service from a lot of similar candidate services based on semantic service chains and multi-QoS values. The algorithms can improve the correctness and automation performances of automated semantic web services composition. As an example, a concrete composite process is analyzed. Experimental results show the validity of the composite process.

Efficient Composition of Semantic Web Services with End-to-End QoS Optimization

The efficiency of QoS-aware service composition is important since most service composition problems are known to be NP-hard. With the growing number of web services, service composition is like a decision problem on selecting services or/and execution plans to satisfy the users＇ end-to-end QoS requirements （e.g. response time, throughput）. Composite services with the same functionality may have dif-ferent execution plans, which may cause different end-to-end QoS. This paper presents a model combining semantic data-links and QoS, which leads to an efficient approach to automatic construction of a composite service with optimal end-to-end QoS. The approach is based on a greedy algorithm to select both services and execution plans for composite services. Empirical and theoretical analyses of the approach show that its time complexity is O（mn2） for a repository with n services and an ontology with m concepts. Moreover, the approach increases linearly in time when using an index to search services in the repository. Tests with a repository with 20 000 services and an ontology with 300 000 concepts show that the algorithm significantly outperforms current existing algorithms in terms of composition efficiency while achieving optimal end-to-end QoS.

An automatic subdigraph renovation plan for failure recovery of composite semantic Web services

A Web service-based system never fulfills a user＇s goal unless a failure recovery approach exists. It is inevitable that several Web services may either perish or fail before or during transactions. The completion of a composite process relies on the smooth execution of all constituent Web services. A mediator acts as an intermediary between providers and consumers to monitor the execution of these services. If a service fails, the mediator has to recover the whole composite process or else jeopardize achieving the intended goals. The atomic replacement of a perished Web service usually does not apply because the process of locating a matched Web service is unreliable. Even the system cannot depend on the replacement of the dead service with a com- posite service. In this paper, we propose an automatic renova- tion plan for failure recovery of composite semantic services based on an approach of subdigraph replacement. A replacement subdigraph is posed in lieu of an original subdigraph, which includes the failed service. The replacement is done in two separate phases, ofltine and online, to make the recovery faster. The ofitine phase foresees all possible subdigraphs, pre-calculates them, and ranks several possible replacements. The online phase compensates the unwanted effects and executes the replacement subdigraph in lieu of the original subdigraph. We have evaluated our approach during an experiment and have found that we could recover more than half of the simulated failures. These achievements show a significant improvement compared to current approaches

Reducing semantic bias of annotations for semantic web service discovery

In order to improve the effectiveness of semantic web service discovery, the semantic bias between an interface parameter and an annotation is reduced by extracting semantic restrictions for the annotation from the description context and generating refined semantic annotations, and then the semantics of the web service is refined. These restrictions are dynamically extracted from the parsing tree of the description text, with the guide of the restriction template extracted from the ontology definition. New semantic annotations are then generated by combining the original concept with the restrictions and represented via refined concept expressions. In addition, a novel semantic similarity measure for refined concept expressions is proposed for semantic web service discovery. Experimental results show that the matchmaker based on this method can improve the average precision of discovery and exhibit low computational complexity. Reducing the semantic bias by utilizing restriction information of annotations can refine the semantics of the web service and improve the discovery effectiveness.

Efficient semantic web service matching using common ontology

To solve the bottleneck problem in centralized service discovery methods,a novel architecture based on domain ontology for semantic service discovery is proposed.This distributed architecture can adjust the domain partition and allocate system resources automatically.The characteristics of this mechanism are analyzed,including scalability,self-organization and adaptability.In this mechanism,semantic web service discovery is separated into two parts.First,under balance tree topology,registry proxy can rapidly forward requests to the objective registry center,and avoid the bottleneck problem.Secondly,a semantic distance based service matching algorithm is proposed to promote the effect of service searching.The results of simulation experiments show that the proposed mechanism can serve as a scalable solution for semantic web service publication and discovery.And the improved matching algorithm has higher recall and precision than other algorithms.

An Edge-Based Approach for Semantic Matchmaking of Service Capabilities

Semantic Web Services is an emerging technology that promises to enable dynamic, execution-time discovery, composition, and invocation of Web Services. Semantic matchmaking plays a vital role in the automated and dynamic discovery process of Semantic Web Services and consists in measuring the semantic distance between a requested service and an advertised one. In this paper, an innovative approach to effectively compute the semantic distance between Ontology Web Language for Services （OWL-S） annotated services is proposed. First, an edge-based method for measuring the semantic distance between Web Ontology Language （OWL） concepts is presented. Then, a comparison of the proposed measure and the one presented in a recent related work is made in order to show that our method is more efficient and fine-grained. Finally, some equations to compute semantic matchmaking of service capabilities, which are expressed in terms of inputs and outputs, are presented.

Quality Model and Metrics of Ontology for Semantic Descriptions of Web Services

An ontology is a conceptualisation of domain knowledge. It is employed in semantic web services technologies to describe the meanings of services so that they can be dynamically searched for and composed according to their meanings. It is essential for dynamic service discovery, composition, and invocation. Whether an ontology is well constructed has a tremendous impact on the accuracy of the semantic description of a web service, the complexity of the semantic definitions, the efficiency of processing messages passed between services, and the precision and recall rates of service retrieval from service registrations. However, measuring the quality of an ontology remains an open problem. Works on the evaluation of ontologies do exist, but they are not in the context of semantic web services. This paper addresses this problem by proposing a quality model of ontology and defining a set of metrics that enables the quality of an ontology to be measured objectively and quantitatively in the context of semantic descriptions of web services. These metrics cover the contents, presentation, and usage aspects of ontologies. The paper also presents a tool that implements these metrics and reports a case study on five real-life examples of web services.

A Semantic Matchmaker for Ranking Web Services

This paper is concerned with the matchmaker for ranking web services by using semantics. So far several methods of semantic matchmaker have been proposed. Most of them, however, focus on classifying the services into predefined categories rather than providing a ranking result. In this paper, a new method of semantic matchmaker is proposed for ranking web services. It is proposed to use the semantic distance for estimating the matching degree between a service and a user request. Four types of semantic distances are defined and four algorithms are implemented respectively to calculate them. Experimental results show that the proposed semantic matchmaker significantly outperforms the keywordbased baseline method.

Hybrid QoS-aware semantic web service composition strategies

Hybrid QoS model which consists of certain and uncertain expressions has strong power of semantic QoS description. For solving the hybrid QoS-aware semantic web service composition problem, this paper presents an Uncertain Multi-attribute decision making based Composition algorithm （UMC）. The UMC includes two parts. First, UMC-Core can be used to synthetically evaluate the hybrid service quality information. Second, UMC-DH （Distributed and Heuristic framework for UMC） aims at enhancing the run-time performance of UMC when the problem space increases. The simulation results show that the UMC has lower execution cost, higher approximation ratio and success ratio than other similar approaches.