Yuliang Shi

Formal analysis of compatibility of Web services via CCS

Compatibility of Web services states the fitness of service peers that interact each other. It covers both static properties and dynamic behavior of Web services. Most researches deal with compatibility issue in the context of static checking. In this paper, we use a formal method, say CCS, to describe dynamic behavior of Web services. The formalization brings us the capability of reasoning on the dynamic aspects. We discuss compatibility at different levels so that we can clarify the impacts of it on composition and substitution of Web services. We also pay attention to context-independent substitutability which is useful in practice.

Exception handling of workflow for Web services

When solving problems such as enterprise information integration and interoperation across heterogeneous repositories, Web services and workflow are extensively used. Due to the nature of modularity, openness and encapsulation, traditional exception handling strategies can hardly meet the demands in the Web service setting. In this paper, we put forward a strategy based on constraint rules of Web services and the position of service nodes. We also design a framework to support exception handling dynamically during the execution of workflow.

Compatibility Analysis of Web Services

The compatibility analysis is absolutely necessary for guaranteeing the correct composition of Web services, no matter what styles the composition takes, statically or dynamically. In this paper, we provide a formalization of Web services behavior using the approach of automata. With this understanding, we propose a definition of role among Web services interactions. As a result, we can check whether two or more Web services are compatible in collaboration or not.

Analysis of web services composition and substitution via CCS

Web services composition is a key issue in web service research area. Substitution of service is closely related with composition and important to robustness of service composition. In this paper, we use process algebra as formalism foundation modeling and specifying web services and reasoning on behavioral features of web services composition. We analyze some cases that have effects on design and implementation of composition. Upon that, and based on definition of composition, we study substitution. As to the problem of how to substitute a component web service, we present a relation. Any new selected web services can substitute old component service independent of context and take part in composition successfully in the case that they satisfy criteria of this relation.

TDWF: A Workflow Model Based on Cooperation of Web Services

Currently technologies of Web services have greatly developed and provided a new application platform for CSCW. For a business process across enterprises, cooperation of multiple Web services is usually required to achieve the final goal. However, most current Web services choreography proposals, such as BPEL4WS or WSCI, only provide a fixed execution flow, lacking of flexibility and adaptability. In this paper, we propose a flexible workflow model TDWF, which can specify the execution process of Web services according to task dependency information, so that the Web services can be composed dynamically. We also put forward an algorithm to verify the correctness of the composition process. Besides, the proposed compensation mechanism of workflow could properly satisfy the requirements of end users

A method to select the optimum web services

Emerging web services standards enable the development of large-scale applications in open environments. With the increasingly emerging web services, one of the main problems is not to find out the required services, but to select the optimum one from a set of requirements-satisfying services. In this paper, we propose a workflow-organization-model-based method to compute web services reputation values, then combine the reputation values with QoS-based objective quality values as the judgment standard to provide to users. Based on these values, users can select the optimum web service to execute.

A Formal Specification for Web Services Composition and Verification

Due to the promising features of Web services, their deployment and research are booming. Among them, various techniques for Web service composition have been developed. In this paper, we propose a new composition framework. We use automata to describe behaviors of Web services. Each of underlying Web services can interact with others through asynchronous messages passing according to its interaction role (client or server). All these messages are recorded by a virtual global observer and the observation result is just the composition conversation of Web services. We also develop a formal a top-down verification mechanism on this framework and provide some realizable conditions for a successful composition

Dynamic incremental data summarization for hierarchical clustering

In many real world applications, with the databases frequent insertions and deletions, the ability of a data mining technique to detect and react quickly to dynamic changes in the data distribution and clustering over time is highly desired. Data summarizations (e.g., data bubbles) have been proposed to compress large databases into representative points suitable for subsequent hierarchical cluster analysis. In this paper, we thoroughly investigate the quality measure (data summarization index) of incremental data bubbles. When updating databases, we show which factors could affect the mean and standard deviation of data summarization index or not. Based on these statements, a fully dynamic scheme to maintain data bubbles incrementally is proposed. An extensive experimental evaluation confirms our statements and shows that the fully dynamic incremental data bubbles are effective in preserving the quality of the data summarization for hierarchical clustering.

Web service collaboration analysis via automata

It is evidenced that formal analyses are helpful for web services interactions. However, most current web services choreography proposals, such as BPEL4WS or WSCI, only provide notations for describing the message flows in web service collaboration, lacking of reasoning mechanisms to verify the process of interacting among them. In this paper, we present a formalization of web services interaction based on WSCI using the approach of automata. The method can check whether two or more web services are compatible or not in their collaboration.