Fangchun Yang

Web service composition algorithm based on TOPSIS

Abstract Independent quality of service (QoS) registration center is difficult to monitor QoS with lots of requests in Internet environment with a large number of services and lots of service requests. It is able to reduce the load and decrease the failure rate by using multiple QoS registration centers to monitor QoS of some services with lots of requests. In addition, the heterogeneous QoS data close to users habitual expression and adapts to the environment with complexity and uncertainty. This paper introduces a novel Web service composition algorithm based on technique for order preference by similarity to an ideal solution (TOPSIS) (WSCA_TOPSIS) to solve the above difficulties for the first time. WSCA_TOPSIS can support multiple decision-makers and heterogeneous QoS data. It includes three main steps: normalizing decision matrix, evaluating alternatives synthetically and evaluating group alternatives synthetically. Other contributions of the paper include a novel algorithm of aggregating QoS and a set of experiments that demonstrate the benefits and effectiveness of our approach. Experimental results show that the proposed algorithm can better support Web service composition with heterogeneous QoS data and multiple decision-makers.

Privacy-aware RBAC model for web services composition

Abstract Web services collaborative environments are highly automatic, dynamic, and heterogeneous. These characteristics always lead to high risks of services for interaction participants. Hence, it becomes one of the most important things to guarantee that the private information in cross-domain services is not illegally collected, used, disclosed or stored when the Web services are required to combine secure composition. This paper proposes the privacy-aware role based access control model for Web services composition (WSC-PRBAC), which provides protection for private data of users in composite service. The element services are divided into local services and outside services. Because the local service is authorized by users, it is exactly different from other services in the composition. To avoid sending private information to other outside services directly, we define global roles to help access these data in local service. Using global roles can realize a more strict control of the private data. In the end, the experiment and analysis of the proposed model show its and efficiency.

Detecting Feature Interactions in Web Services with Model Checking Techniques

As a platform-independent software system, a Web service is designed to offer interoperability among diverse and heterogeneous applications. With the introduction of service composition in the Web service creation, various message interactions among the atomic services result in a problem resembling the feature interaction problem in the telecommunication area. This article defines the problem as feature interaction in Web services and proposes a model checking-based detection method. In the method, the Web service description is translated to the Promela language-the input language of the model checker simple promela interpreter (SPIN), and the specific properties, expressed as linear temporal logic (LTL) formulas, are formulated according to our classification of feature interaction. Then, SPIN is used to check these specific properties to detect the feature interaction in Web services.

Policy Conflict Detection in Composite Web Services with RBAC

In the Web services environment, RBAC (role-based access control) model is widely accepted as an efficient approach to manage the access control. By defining the authorization relationship between subject roles and object roles in the RBAC, authorization policies are utilized to simplify the authorization management on different Web services. But the scalability and complexity of composite Web services may cause authorization policy conflict. A new authorization policy added to the system may conflict with existing ones and result in authorization chaos and authorization leaking. And when implemented in the composite Web services, policy conflict detection would be of high cost with manually checking. That makes automatic policy conflict detection important to ensure the security of authorizations in the composited Web services. This paper analyzes the features of the authorization policy in the CWS-RBAC (RBAC for composite Web services) and presents methods of detecting policy conflict including subject role propagation conflict, object role composition conflict and context conflict. The experiment designed is to validate the efficiency of each conflict detection method.

SKIP: an efficient search mechanism in unstructured P2P networks

Abstract Search efficiency and accuracy of resource are important considerations for search algorithm in peer-to-peer (P2P) network. Most search algorithms use flooding among neighbor nodes to search relevant resource. However, this usually causes great amount of redundant messages, which results in high search costs and low search precision. In this paper, we use vector space model (VSM) and relevance ranking algorithms to construct overlay network, and a novel search mechanism search with K-iteration preference (SKIP) based on semantic group for P2P networks is proposed to efficiently solve these problems. The key idea of SKIP is to reorder the semantic neighbors of nodes according to relevant scores and to utilize preference selection during the process of query. We analysis and implement the scheme and reveal that the SKIP provides a low overhead on topology maintenance, which can be effectively used in P2P searching and verify it outperformance in higher precision and lower search cost by comparing with current semantic-based searching mechanism gnutella-like efficient searching system (GES).

A Novel Approach to Optimize Information Dissemination in IMS Presence System

Presence is an important service in IMS. The user in IMS would use presence as a necessary component. But the more user uses, the harder presence information transmits. Previous researches show that the traffic increases rapidly with the presentity number grows. In this paper, we propose an approach to optimize information dissemination in IMS Presence System. Comparing with previous researches, a new architecture is set up. In this architecture, presence information transmission is modeled as a growing tree. A k sequence method is proposed to construct the tree. And some key algorithms are introduced for the tree adjustment. With a mathematical analysis, the new method is more suitable for presence information dissemination. And in the experiment, the result shows that the method can do a better job with smaller traffic and jitter.

QoS-based service selection for multiple requests with different classes

As the rapid development of web service, there are more and more services that have similar functional implementations appear on the converged network. Therefore the web service selection technologies help users selecting their services based on users non-functional requirements. However, present works are lack of considering the situations that multiple user requests for the same functional service, not to mention users with different classes/priorities. This paper aims at helping multi-users to select their services from uses perspective and finding a global optimal solution. Comparing with existing service selection technologies, our approach has three advantages: 1) It classifies a services QoS into four types and normalizes these QoS attributes on various dimensions with different metrics and scales. 2) In order to determine how well a service satisfies a users requirements, it gives the satisfaction calculating functions based on prospect theory, which is good at reflecting the fluctuation of user feeling. 3) It uses bipartite graph to solve service selection for multi-users scenario. Besides, users different classes/priorities are also taken into account in satisfaction calculations.

Small business-oriented index construction of cloud data

With the development of cloud computing, data owners (businesses and individuals) are motivated to outsource their local complex database systems to public cloud for flexibility and economic savings. But for the consideration of users privacy, personal data has to be special treatment locally before outsourcing to the cloud server. Considering the large number of data users and documents in cloud, it is crucial for data owner to construct an index for their data collection, which increases the cost of the data owner. Related works focus on the searches on encrypted database but rarely consider the overhead of the index construction for data owner and the extensions of the index. Although traditional index construction methods of information retrieval have been widely studied, direct application of these methods would not be necessarily suitable for our scenario. Thus, enabling an efficient index construction service is of paramount. In this paper, we define and solve the problem of index construction on small business (SBIC). Among various index methods, we choose inverted index method. An inverted index is an index data structure storing a mapping from content to its locations in a set of documents. The purpose of it is to allow fast full text searches.We firstly propose a basic SBIC scheme using Lucene (an open source project for web search engine), and then significantly improve it to meet efficient keyword extraction requirement and multi-type files demand. Thorough analysis design goals(see section 2.3) of proposed schemes is given, extensive experimental results on the dataset further show proposed scheme indeed introduce low overhead on time and space.

Design and Implementation of Load Test for 3G Online Charging System

3G oriented Online Charging System concept is briefly introduced at first. Then the OCS load test requirements are analyzed and the load test scenario is proposed, including the load test manners and scope, major performance benchmark data, full-service oriented traffic model and test output requirements. Based on the load test scenario, the design and implementation of OCS load tester is presented at last, which has been adapted in 3G OCS development and deployment in China Telecom.

Using ‘word of mouth’ to find community structure in an online IMS system

Abstract Presence is a feature that is used widely in lots of system, especially in IMS. The presence system in IMS also provides application developer and end user with a chance to new style applications. But the presence system in IMS has some problems. Previous researches show that the traffic increases rapidly with the presentity number grows. In this study, we would treat the system in a different way by introducing some social networking concepts to the architecture. Moreover, we would focus on how to apply and generate community in the dynamic and online environment. A word of mouth marketing principle would be used to model the community generating procedure. The presence system would works like a marketing environment. Experiment with simple math analysis show this approach is effective for distributed community generating.