Abstract:The determination of such good properties as liveness, deadlock-freeness of a global system is an important field in the study of Petri net systems synthesis. In this paper, the sharing synthesis of Petri net systems, a significant synthesis process, is discussed. The language recursiveness in sharing synthesis process is proposed and proved, and then the language relation formula based on the concurrent language is obtained. These results present a formal tool for the analysis of a large system which contains concurrent behavior. Moreover, this language relation formula can be applied to judge the liveness and deadlock-freeness of the synthesized systems. Necessary and sufficient conditions are developed. Finally, under the given conditions, the liveness of a global system can be determined by the sublanguage of the local systems, and thus can be studied by means of local systems.

Abstract:In order to specify the behaviors of structure-complex Petri nets, the concept of synchronous composition is extended and a method is presented, with which a given structure-complex Petri net can be obtained through the synchronous composition of a set of structure-simple Petri nets, namely S-nets. Firstly, the language characters of S-nets are analyzed with details and the methods to obtain their language expressions are presented. With the synchronous intersection operation of Petri net languages, the language relationships between the structure-complex Petri net and the set of S-nets can be expressed. Based on these works, an algorithm to specify the behaviors of Petri nets especially structure-complex systems is obtained.

Abstract:In distributed modeling and simulation area, it is intractable to comprehend the fundamental principles of optimistic advancing mechanism and implement the optimistic advancing services in RTI (runtime infrastructure) according to HLA (high level architecture) specifications. This paper introduces two different optimistic advancing mechanisms in PDES (parallel discrete event simulation) and HLA, and reveals some important differences between them. For example, the virtual time can be rolled back in PDES, the logical time can not be rolled back in HLA, and an optimistic federate can only roll back its message-scheduling time and must ensure that its rollback won’t influence the advancing of conservative federates. Rollback occurs in a logical process in PDES, but it can only occur in a federate rather than RTI in HLA. In addition, a new implementation mechanism called Zero-Saving is proposed in this paper. With this mechanism, a RTI does not need to save any execution states when optimistic advancing services are implemented. This mechanism has successfully been applied to a RTI named StarLink. The Zero-Saving mechanism adds two new variables into the message retraction handle type RTI::MessageRetraction Handle which is a data type defined by IEEE 1516.1. One variable represents the time stamp of the sent TSO (time stamp order) message, and the other is used to save all federates which receive the message. When a TSO message is sent to RTI, RTI returns the sending federate a message retraction handle with all message-received federates. So RTI knows which federates should be notified to retract the received messages whenever the sending federate uses a message retraction handle to ask RTI to retract a TSO message. The fundamental principles and implementation of optimistic advancing services introduced in this paper are useful for RTI developers.

Abstract:Traditional software process models are mostly static, mechanical, and passive. Traditional approach requires modeler to determine all the possible conditions the software process will encounter and to define explicitly the solutions into a process model. It lacks the ability to allow further deliberations when the modeled environment changes. This paper presents an Agent-based self-adaptive software process model. In this approach, software process is modeled as peers: process Agents. These software process Agents can adapt themselves to the software process environment and act with initiative and autonomy. When the process environment changes, the process agents can dynamically change their behavior to ensure that the development goal can still be achieved.

Abstract:This paper proposes a new scheduling scheme based on priority table design by integrating two characteristic parameters (i.e. deadline and value) of a task. Two real-time scheduling algorithms from the scheme are presented: earliest deadline value (EDV) and value earliest deadline (VED). Furthermore, how to implement the two algorithms using multi-linked lists is given, including task acceptance policy and task completion/abortion policy. This scheme can also be applied to integrate two other characteristic parameters or even three characteristic parameters of a task. Based on hit value ratio, weighted guarantee ratio and differentiated guarantee ratio, the performance of the VED and EDV algorithms are analyzed, the experimental results show that the VED and EDV algorithms can improve the performance compared to the classical EDF (earliest deadline first) and HVF (highest value first) algorithms under all workload conditions.

Abstract:With the rapid advances of wireless communication and positioning techniques, tracking the positions of mobile objects is becoming increasingly feasible and necessary. Traditional spatial index structures are not suitable for indexing mobile objects because of numerous updating operations. A coordinates-organization hybrid-feature indexing structure called C²OR-Tree is firstly introduced in this paper to index the current positions of the hierarchically organized mobile objects. Based on C²OR-Tree, a notable activated-insertion and deferred-deletion (AIDD) algorithm is presented to deal with the bulk updates of the objects coordinates. In view of the local reconstruction characteristic of the C²OR-Tree, AIDD algorithm gives an efficient implemention of the bulk updates with the integration of the insert processing of the updated objects and the earmark processing of the updated regions. Experiment shows that C²OR-Tree can preserve its satisfying query response capability even after many times of AIDD operations.

Abstract:Due to the variation of the tasks attributes, the behavior of soft real-time systems, such as multimedia application, is becoming increasingly unpredictable. Under this circumstance, the scheduling algorithms, which depend on the tasks static attributes, cant give a usable and efficient resource allocation to those soft real-time systems. This paper presents an elastic scheduling algorithm for flexible workload. Based on sampling the total number and lost number of the task instances, this algorithm adjusts the number of task instances executing in the next sampling period to guarantee the tasks basic QoS (quality of service) and to improve the system resource utilization and concurrency in the next sampling period. This paper analyzes the model and evaluates its performance. Simulation results show that, besides improving resource utilization, this algorithm has good stability and convergence.

Abstract:The aim of this paper is to create a new anomaly detection model based on rules. A detailed classification of the LINUX system calls according to their function and level of threat is presented. The detection model only aims at critical calls (I.e. The threat level 1 calls). In the learning process, the etection model dynamically processes every critical call, but does not use data mining or statistics from static data. Therefore, the increment learning could be implemented. Based on some simple predefined rules and refining, the number of rules in the rule database could be reduced dramatically, so that the rule match time can be reduced effectively during detection processing. The experimental results clearly demonstrate that the detection model can effectively detect R2L, R2R and L2R attacks. Moreover the detected anomaly is limited in the corresponding requests, but not in the entire trace. The detection model is fit for the privileged processes, especially for those based on request-responses.

Abstract:Web application servers (WASs) provide a web computing infrastructure for distributed components. The component structure of statically configured distribution prevents web applications from being adaptive to the changing environmental conditions at runtime. To meet the requirement of dynamic redistribution, WASs should provide the capability to support component migration. The most challenging problem is to maintain component consistency during such a component migration. To resolve this inconsistency problem, some kinds of component migration constrains (CMC) are defined in this paper. A component migration model for J2EE (Java 2 platform enterprise edition) application servers is proposed, and SLB_Copy, SFB_Copy and EB_Copy component migration algorithms are presented. It is proved that SLB_Copy, SFB_Copy and EB_Copy migration algorithms all satisfy the CMC constrains. At present, the migration model is implemented in a J2EE application server, referred to as WebFrame 2.0, and these algorithms are applied to provide numerous services such as the adaptive load balancing service and the failover service.

Abstract:Differentiated services (DiffServ) is a scalable architecture for supporting quality of services (QoS), and video multicast is the application which needs network to support QoS guarantee. To accommodate to heterogeneous network and host, it is a good idea to transmit video in a few layers. The paper proposes LVMM (layered video multicast meter) and LVMF (layered video multicast forwarder) algorithms for distribution of the layered video multicast in DiffServ networks. The method needs only one multicast address and its validity is verified using ns-2 simulator.

Abstract:At present, research on secure multi-party computation is of great interest in modern cryptography. It should be acknowledged that if any function can be computed securely, then it results in a very powerful tool. In fact, all natural protocols are, or can be rephrased to be, special cases of the multi-party computation problems. Design and analysis of the special multi-party computation protocols is meaningful and has attracted much interest in this field. Based on the combination of a public-key cryptosystem of the homomorphic encryption and on the theoretic construction relying on the F-hiding assumption, a protocol for comparing information of equality is proposed. The protocol needs only a single round of interaction and ensures fairness, efficiency and security. The protocol is fair, which means that one party knows the sound result of the comparison if and only if the other one knows the result. The protocol is efficient with the help of an oblivious third party for calculating. However, the third party cannot learn any information about the participant's private inputs and even about the comparison result, and cannot collude with any participant. The protocol is secure for the two participants, that is, any information about their secret input will not leak except the final computation result. A precise proof of security of the protocol is presented. Applications of this protocol may include private bidding and auctions, secret ballot elections, commercial business, identification in a number of scenarios and so on. It is believed that the protocol may be of practical significance for electronic transaction.

Abstract:With the rapid development of e-business, web applications based on the Web are developed from localization to globalization, from B2C(business-to-customer) to B2B(business-to-business), from centralized fashion to decentralized fashion. Web service is a new application model for decentralized computing, and it is also an effective mechanism for the data and service integration on the web. Thus, web service has become a solution to e-business. It is important and necessary to carry out the research on the new architecture of web services, on the combinations with other good techniques, and on the integration of services. In this paper, a survey presents on various aspects of the research of web services from the basic concepts to the principal research problems and the underlying techniques, including data integration in web services, web service composition, semantic web service, web service discovery, web service security, the solution to web services in the P2P (Peer-to-Peer) computing environment, and the grid service, etc. This paper also presents a summary of the current art of the state of these techniques, a discussion on the future research topics, and the challenges of the web services.

Abstract:The aim of image restoration is to recover the original uncorrupted images from noisy, blurred ones. A linear image restoration algorithm based on a wavelet-domain local gaussian model is proposed in this paper. The wavelet-domain local gaussian model approximates the local probability distribution of the wavelet coefficients with a single gaussian function. Because the wavelet-domain local gaussian model adaptively characterizes the local statistic properties of real-world images, the algorithm presented in this paper specifies the prior distribution of the real-world image through the model and converts the restoration problem to an constrained optimization one which can be solved with the conjugate gradient method. Experimental results show that the algorithm can properly retrieve various kinds of edges, and the PNSR (peak signal to noise ratio) and subjective visual effect of the restored images are improved significantly.

Abstract:Representing a curve contained in a surface is very important in dealing with path generation in computer numerical control (CNC) machining and the trimming issues that frequently occur in the field of CAD/CAM. This paper develops methods for tangent direction continuous (G¹) and both tangent direction and curvature continuous (G²) interpolation of a range of points on surface with specified tangent and either a curvature vector or a geodesic curvature at every point. As a special case of the interpolation, the blending problems of curves on surface are also discussed. The basic idea is as follows: with the help of the related results of differential geometry, the problem of interpolating curve on a parametric surface is converted to a similar one on its parametric plane. The methods can express the G¹ and G² interpolation curve of an arbitrary sequence of points on a parametric surface in a 2D implicit form, which transforms the geometric problem of surface intersection, usually a troublesome issue, into the algebraic problem of computing an implicit curve in displaying such an interpolation curve. Experimental results show the presented methods are feasible and applicable to CAD/CAM and Computer Graphics.

Abstract:Painting system based on texture mapping is often limited by the model's parameterization in a 2D texture space. For models with complex topologies or complicated distributions of the structural details, finding the parameterization can be very difficult and usually must be performed manually. Here a novel data representation and a system for direct painting on 3D surface are presented. By creating 3D colored points for each triangle, the system can support a great variety of painting operations similar to the conventional 2D pixels editor. One key ingredient of this method is a novel adaptive data representation including geometry, topology and color. This technique is called the imaged geometry, which allows users to treat each triangle as a triangle image, and to paint the points on 3D triangle surface without any parameterization. This system can take any triangle model as an input and produces an output with colored points on triangles of the model surface. Because this method is adaptive, details are created in the triangles required by the texture painting, which reduces memory usage. Based on the imaged geometry, the models with complex topologies can be painted in an easy way.

Abstract:In this paper,the 2003 year's application for and supporting General Program,Key Program,National Science Fund for Distinguished Young Scholars,and Major Research Plan by Computer Science Division of Information Science Department of National Natural Science Foundation of China(NSFC)are summarized.Due to volumes of the General Program and their fargoing application,further analysis and summarization are performed from several aspects.