15574881
A Tuplespace-Based Middleware for Semantic Web Services Using SWRL
Coordination is a vital aspect of any type of interaction between computer agents in open distributed systems such as the Web. As distributed systems become more ubiquitous, autonomous and complex, the need to ground them on common data model grows stronger. In particular, Semantic Web services are based on synchronous message exchange, thus being incompatible with the REST architectural model of the (Semantic) Web. Recent advances in middleware technologies propose semantic aware tuplespaces as an infrastructure for coping with these issues. However, all of the existing related works do not support rule in their extensions of tuplespace. This paper presents a RuleSpaces based on a combination of tuplespace computing and Semantic Web Rule Language. We describe overview of the conceptual model and discuss the necessary extensions to the original tuplespace. An initial version of the RuleSpaces prototype system has been implemented.
15542808
An Agent-based Policy Aware Framework for Web Services Security
The security of Web services has become one of the important research topics about the application of Web services. In this paper, we propose an agent-based policy aware framework for Web services security. In this framework, a policy language called ReiT which is a declarative language based on the rules and ontologies is introduced. The non-structural knowledge is represented by rules and the structural temporal knowledge is represented by ontology. Moreover, we propose a mixed reasoning mechanism to evaluate the ReiT policy. The access control policy including the context of the user and Web services is evaluated by the reasoner. In addition, we present a policy aware BOID agent to authorize the access control of the Web services. And we implement the policy aware BOID agent by extending the JADE platform.
43513684
A representation theorem for recovering contraction relations satisfying wci
A notion of an image structure associated with the canonical epistemic state is introduced. Based on it, we get a representation result for recovering contraction inference relations satisfying the condition weak conjunctive inclusion (wci) in terms of F-standard epistemic AGM states. In effect, this result establishes a representation theorem for belief contraction functions satisfying AGM postulates (k-1) - (k-7), and Rott's (wci) and (k-8c), and hence generalizes Rott's corresponding result in the finite framework.
2517026
On Dynamic and Concurrent Model of Web Service Components
The researches of Web service fasten on composition process, and are lack of the formalized description on dynamic attributes of service component itself. Aiming to these, a new dynamic and concurrent model of Web service component is presented. Firstly, this paper analyzes the process of state transition of service component under certain actions, and then depicts the dynamic transition process of service component with the state transition graph. At last, the physical representation method in memory and the algorithms to judge equivalence of state transition graph are given. Comparing with existing researches, the dynamic evolvement of service component under the actions is considered, and the algorithm to judge equivalence of service components provides an effective tool for model verification.
16775013
A Dynamic Trust Model for the Multi-agent Systems
Internet provides a fertile medium for new breeds of computer viruses. Many people who have access to a wealth of information via Internet are attacked by more computer viruses than they can effectively process. We present a dynamic computer virus detection model that can detect known viruses and previously unknown viruses to prevent information systems from damage. This model is inspired by biological immune systems that protect the body against damage from pathogens. The architecture of this model, the formal definitions of self nonself antigen, antibody, and vaccine gene library are introduced. Furthermore, the evolution of self and nonself, the generation of the antibody, the evolution of the virus vaccine gene, and the detection of the antigen are depicted. Experiment results show that this model has better capacity of self-adaptability and self-learning in detecting unknown viruses than traditional models.
8899940
Sketch retrieval based on spatial relations
In this paper, we propose an effective approach for sketch retrieval. Given sketches are firstly decomposed into basic geometric primitives and represented as a topological graph that encodes both the intrinsic attributes of the primitives and their relationships. The graph spectrum descriptor is then adopted to translate the graph-match into the computation of vector distances. Sketches retrieval is finally done by means of similarity calculation of feature vectors based on dimensionality reduction. The relevance feedback is also introduced to refine the retrieval results. Experiments prove the effectiveness and efficiency of the proposed method in sketch content retrieval and user independent.
17604686
Enhanced high-performance distributed coordination function for IEEE 802.11 multi-rate LANs
To compensate for the effects of fading in wireless channels, IEEE 802.11 systems utilize a rate-adaptation mechanism to accomplish a multi-rate capability. However, the IEEE 802.11 distributed coordination function results in a fundamental performance anomaly in multi-rate networks; namely, when stations with different transmission rates collide, the throughput performance of the high-rate station is significantly degraded by the relatively longer channel occupancy time of the low-rate station. This study resolves this problem through the use of an enhanced high-performance distributed coordination function (EHDCF) protocol. While most existing solutions to the multi-rate performance anomaly problem have the form of simple contention-based protocols, EHDCF has two modes, namely a contending mode and an active mode. In the proposed protocol, new stations joining the network are assigned a contending mode, but switch to an active node (and are therefore permitted to transmit data packets) as soon as they have gained access to the channel. Having transmitted a data packet, the active node then selects the next transmission station in accordance with a probability-based rule designed such that the high-rate stations within the network receive a greater number of transmission opportunities than the low-rate stations. The simulation results show that the EHDCF protocol not only yields a significant improvement in the network throughput but also guarantees the temporal fairness of all the stations. Copyright q 2009 John Wiley & Sons, Ltd.
11362746
A novel approach to extract colon lumen from CT images for virtual colonoscopy
An automatic method has been developed for segmentation of abdominal computed tomography (CT) images for virtual colonoscopy obtained after a bowel preparation of a low-residue diet with ingested contrast solutions to enhance the image intensities of residual colonic materials. Removal of the enhanced materials was performed electronically by a computer algorithm. The method is a multistage approach that employs a modified self-adaptive on-line, vector quantization technique for a low-level image classification and utilizes a region-growing strategy for a high-level feature extraction. The low-level classification labels each voxel based on statistical analysis of its three-dimensional intensity vectors consisting of nearby voxels. The high-level processing extracts the labeled stool, fluid and air voxels within the colon, and eliminates bone and lung voxels which have similar image intensities as the enhanced materials and air, but are physically separated from the colon. This method was evaluated by volunteer studies based on both objective and subjective criteria. The validation demonstrated that the method has a high reproducibility and repeatability and a small error due to partial volume effect. As a result of this electronic colon cleansing, routine physical bowel cleansing prior to virtual colonoscopy may not be necessary.
27275974
Distributed Spatial Catalog Service on the CORBA Object Bus
Spatial catalog service is a necessary component for distributed geographic information. Spatial catalog services provide the capabilities for organizing and managing spatial metadata. Catalog services simplify the process of data discovery in a large spatial database, facilitate data transfer, and help data fusion.This paper presents a software architecture for spatial catalog services. We first discuss the general concept of spatial catalog facilities and the logical model of spatial catalog services. We then introduce the distributed object-oriented model for spatial catalog services based on the industrial standard Common Object Request Broker Architecture (CORBA). The core components of spatial catalog services, catalog and catalog registry, are described in detail with the CORBA Interface Definition Language (IDL). Examples are given to illustrate the structure of the catalog component and its relations with other service components in a distributed GIS. The model provides a common interface to spatial catalogs and related data no matter how catalogs are defined, what formats they use, and where they are located. It provides crucial services in a distributed Geographic Information System.
1252893
A Configurable Web Service Performance Testing Framework
More and more softwares based on web service technologies are developed. Before their releases on the Internet, it is necessary to evaluate these systems' performance, especially their response time under different workload pressures. However, existing performance testing benchmarks and tools for web service applications are difficult to adapt to various user-specific testing purposes. This paper proposes a configurable web service performance testing framework which contains client module, application server module and database module. Client module, by using the network cooperation method that one central client drives several other clients, adapts to a great number of concurrent customers to request web services. Application server module contains web services under testing and external supporting web services, each of which is configured as a plug-in. The process to realize mixed ratio of web service interactions is similar to dealing cards and adapts to different commercial application characteristics. In database module, the data model including table and attribute dependence can be customized, and the data scale initialization can be resized according to the topology of above dependence. As such, this framework allows testers to dynamically define their data model, customize their scale of database, configure their transaction characteristics, deploy their application strategies and confirm their performance metrics..
13896042
Posture control of a dual-crawler-driven robot
This paper deals with a tracked robot that consists of the proposed crawler module, in which a planetary gear reducer is used as the power transmission device to give two different outputs with just one actuator. This under-actuated system could perform posture control through the interaction between the front and rear modules. On occasion, the posture that the front module is lifted up can make the robot overcome obstacles actively and easily. To find out the controllable postures, the static analysis of the robot has been conducted. In this paper, we provide the control strategy for performing the posture control, and propose the control methods including direct, indirect, and cooperative control to conduct the posture control. Experimental tests show the effectiveness of the control methods.