In order to formally reason and verify web services composition described by web services choreography specification WS-CDL,a typed formal model named typed Abstract WS-CDL（web services choreography description language）for WS-CDL specifications is proposed.In typed Abstract WS-CDL,the syntax of type and session,typing rules and operational semantics are formalized;the collaborations of web services are formally described by sessions;the operational semantics of a session can help to formally reason the execution of the choreography;the typing rules can help to formally check the data type consistency of exchanged information between web services and capture run-time errors due to type mismatches.Particularly,the concepts of type assumption set extension and type assumption set compatibility are proposed,and the merging algorithm of type assumption sets is defined so as to eliminate type assumption conflict.Based on the formal model,typed mapping rules for mapping web services choreography to orchestration is also defined.With the typed mapping rules,orchestration stubs and their type assumption sets can be generated from a given choreography; thus, web services composition can be verified at choreography and orchestration levels,respectively.The model is proved to have properties of type safety,and how the model can help to reason and verify web services composition is illustrated through a case study.
Name ambiguity is a critical problem in many applications, in particular in online bibliography sys-tems, such as DBLP, ACM, and CiteSeerx. Despite the many studies, this problem is still not resolved and is becoming even more serious, especially with the increasing popularity of Web 2.0. This paper addresses the problem in the academic researcher social network ArnetMiner using a supervised method for exploiting all side information including co-author, organization, paper citation, title similarity, author＇s homepage, web constraint, and user feedback. The method automatically determines the person number k. Tests on the researcher social network with up to 100 different names show that the method significantly outperforms the baseline method using an unsupervised attribute-augmented graph clustering algorithm.
In this paper, we propose Term-based Semantic Peerto-Peer Networks （TSPN） to achieve semantic search. For each peer, TSPN builds a full text index of its documents. Through the analysis of resources, TSPN obtains series of terms, and distributes these terms into the network. Thus, TSPN can use query terms to locate appropriate peers to perform semantic search. Moreover, unlike the traditional structured P2P networks, TSPN uses the terms, not the peers, as the logical nodes of DHT. This can withstand the impact of network chum. The experimental results show that TSPN has better performance compared with the existing P2P semantic searching algorithms.
In order to reduce the traffic load and improve the availability of the shared resources in unstructured P2P networks, a caching scheme combining alternative index and adaptive replication （AIAR） is presented. AIAR uses random walk mechanism to disperse the caching information of resources in the network based on its power-law characteristic, and dynamically adjusts replicas according to the visit frequency on resources and the degree information of peers. Subsequent experimental results show that the proposed AIAR scheme is beneficial to improve the search performance of success rate and respond speed. In addition, compared to some existing caching scheme, AIAR can perform much better in success rate, especially in a dynamic environment.
An access control model is proposed based on the famous Bell-LaPadula （BLP） model.In the proposed model,hierarchical relationships among departments are built,a new concept named post is proposed,and assigning security tags to subjects and objects is greatly simplified.The interoperation among different departments is implemented through assigning multiple security tags to one post, and the more departments are closed on the organization tree,the more secret objects can be exchanged by the staff of the departments.The access control matrices of the department,post and staff are defined.By using the three access control matrices,a multi granularity and flexible discretionary access control policy is implemented.The outstanding merit of the BLP model is inherited,and the new model can guarantee that all the information flow is under control.Finally,our study shows that compared to the BLP model,the proposed model is more flexible.
PeerMD, a P2P molecular dynamics simulation frame-work based on Web services is proposed. It utilizes rich free CPU time and network bandwidth of P2P networks to provide enough resources for dynamics simulation of bio-macromolecule, and has resolved the problem that it is difficult to interoperate between heterogeneous peers in P2P environment through Web services. Structure of PeerMD is given. Function, input and output of molecular dynamics simulation Web service are defined. Processes of publishing, discovering and invoking of molecular dynamics simulation Web service based on multi-level SuperPeer are given. A protocol system of PeerMD is implemented on a basic P2P platform JXTA, and experimental simulations of tumor necrosis fact alpha （TNF-α） and two mutations of it are executed on the protocol system. Simulation results show that PeerMD can speed up molecular dynamics simulation perfectly.
Quorum system is a preferable model to construct distributed access control architecture, but not all quorum system can satisfy the requirements of distributed access control architecture. Aiming at the dependable problem of authorization server in distributed system and combining the requirements of access control, a set of criterions to select and evaluate quorum system is presented. The scheme and algorithm of constructing an authorization server system based on Paths quorum system are designed, and the integrated sys- tem performance under some servers attacked is fully analyzed. Role-based access control on the Web implemented by this scheme is introduced. Analysis shows that with certain node failure probability, the scheme not only has high dependability but also can satisfy the special requirements of distributed access control such as real-time, parallelism, and consistency of security policy.
