22537497
ACES: An efficient admission control scheme for QoS-aware web servers
The unpredictability of server response performance hinders the advance of new application on the Internet. In this paper, we present an efficient admission control algorithm, ACES, based on the server workload characteristics. The admission control algorithm ensures the bounded response time from a web server by periodical allocation of system resources according to the resource requirements of incoming tasks. By rejecting requests exceeding server capacity, the response performance of the server is well maintained even under high system utilization. The resource requirements of tasks are estimated based on their types. A double-queue structure is implemented to reduce the effects caused by estimation inaccuracy, and to exploit the spare capacity of the server, thus increasing the system throughput. The admission control algorithm can be used for server overload control and for QoS provisioning of service differentiating Internet servers. Response delays of accepted tasks are bounded by the desired predefined time period. Theoretical analyses and experimental studies show that the ACES algorithm provides desirable throughput and bounded response delay to the tasks, without any significant impact on the aggregate throughput performance of the system under various workload situations.
8488192
Session-based overload control in QoS-aware Web servers
With the explosive use of the Internet, contemporary Web servers are susceptible to overloads and their services deteriorate drastically and often cause denial of services. In this paper, we propose two methods to prevent and control overloads in Web servers by utilizing the session-based relationship among HTTP requests. We first exploited the dependence among session-based requests by analyzing and predicting the reference patterns. Using the dependency relationships, we have derived traffic conformation functions that can be used for capacity planning and overload prevention in Web servers. Second, we have proposed a dynamic weighted fair sharing (DWFS) scheduling algorithm to control overloads in Web servers. DWFS is distinguished from other scheduling algorithms in the sense that it aims to avoid processing of requests that belong to sessions that are likely to be aborted in the near future. The experimental results demonstrate that DWFS can improve server responsiveness by as high as 50% while providing QoS support through service differentiation for a class of application environment.
3576
Collapsibility and Consistency in Quantified Constraint Satisfaction
The concept of consistency has pervaded studies of the constraint satisfiction problem. We introduce two concepts, which are inspired by consistency, for the more general framework of the quantified constraint satisfaction problem (QCSP). We use these concepts to derive, in a uniform fashion, proofs of polynomial-time tractability and corresponding algorithms for certain cases of the QCSP where the types of allowed relations are restricted. We not only unify existing tractability results and algorithms, but also identify new classes of tractable QCSPs.
43818812
Piecewise linear modulation model of handwriting
A new piecewise linear modulation model of handwriting is proposed. In this model, the velocity of handwriting trajectory is modeled as the impulse response of a time varying second order system. For mathematical tractability, the entire trajectory is segmented into several non-overlapping frames, while the natural frequency and the damping factor of the system are assumed to vary linearly with time in each frame and are continuous along the entire trajectory. In other words, handwriting is regarded as an oscillation modulated by a continuous and piecewise linear signal. The parameters of this model are estimated by Powell's optimization algorithm which does not require the computation of the first order derivative. The number and lengths of the frames are decided by a modified binary search algorithm along with the estimation of parameters. This model has achieved very high data compression rate as well as accurate reproduction of real handwriting.
15665012
Progressive auction based resource allocation in service-oriented architecture
The emerging paradigm of distributed Web services has promised seamless business integration across the Internet that shares not only computing power but also applications. One major challenge is resource allocation to each end user in an economically efficient and low latency manner. A common solution is proportional sharing where each user gets his resource in proportion to the predetermined weight. However, this does not allow users to differentiate the value of their services and to dynamically adjust the weights. A resource reservation mechanism may improve the information and service sharing but usually introduces a high latency. In this paper, we propose a progressive auction based market mechanism for resource allocation that allows user differentiation of the service value and ensures the resource acquisition latency to be limited only to the communication delay in service-oriented architecture (SOA) systems. We present a service sharing prototype for selecting services for further business process composition or solution creation and show experimental results on the formation of reliable user ranking in resource sharing through the progressive auction.
5485929
ITTALKS: A Case Study in the Semantic Web and DAML
Effective use of the vast quantity of information now available on the web will require the use of "Semantic Web" markup languages such as the DARPA Agent Markup Language (DAML). Such languages will enable the automated gathering and processing of much information that is currently available but insufficiently utilized. Effectively, such languages will facilitate the integration of multi-agent systems with the existing information infrastructure. As part of our exploration of Semantic Web technology, and DAML in particular, we have constructed ITTALKS, a web-based system for automatic and intelligent notification of information technology talks. In this paper, we describe the ITTALKS system, and discuss the numerous ways in which the use of Semantic Web concepts and DAML extend its ability to provide an intelligent online service to both the human community and the agents assisting them.
19452291
Cross-Jurisdictional Activity Networks to Support Criminal Investigations
Border and transportation security is a critical part of the Department of Homeland Security's (DHS) national strategy. DHS strategy calls for the creation of "smart borders" where information from local, state, federal, and international sources can be combined to support risk-based management tools for border-management agencies. Sharing cross-jurisdictional law enforcement data is important because criminals take advantage of the fact that information sharing between law enforcement jurisdictions is very limited. Challenges to information integration in this important domain include policy and privacy concerns, data security requirements, semantic or schema-level matching of legacy system data, and identity matching. The BorderSafe project leverages the skills and experiences of a diverse group of researchers, law enforcement officials, and government agencies to address data sharing needs in the Southwest United States. Our demo presents a framework for combining law enforcement data across jurisdictions to support criminal investigation and describes how that framework was used in combining three large, overlapping datasets to produce an integrated system for visualizing criminal activity networks.