17013178
Smart supply web: an application of web-based data and workflow mediation
This paper describes our vision of a Supply Web as the next major advance in the e-commerce world in terms of how e-services are delivered. After highlighting shortcomings of existing supply chain solutions, we give an architecture to show how three important technologies, namely, workow systems, data integration and on-line decision support, will have to come together to enable seamless deployment of e-service supply web solutions. We rst discuss research eorts (namely, XRL, YAT and DecisionFlows) that support the three technologies separately, and then describe the challenges of integrating them eectively.
16012186
A fine-grained, controllable, user-to-user delegation method in RBAC
This paper addresses the issues surrounding user-to-user delegation in RBAC. We show how delegations can be incorporated into the RBAC model in a simple and straightforward manner. A special feature of the model is that it allows fine-grained control over what rights a user wishes to delegate as opposed to delegation at the role level where all the rights of a role must be delegated. In addition, the model provides a rich set of controls regarding further delegations of a right, generic constraints that further control delegations, and an innovative model for revocations. Properties of both delegation and revocation are discussed, and our work is compared with other related research.
206778468
A performance study of general grid structures for replicated data
Recently, there has been considerable interest in the study of replica-control protocols which are based on organizing several copies of an object into logical structures, such as rectangular grids. In addition to high availability, another objective in exploiting such structures is to improve the degree of load sharing in a system. The authors extend the scope of grid structures to general grids, which allow holes in various positions of a rectangular structure and are useful to consider because they often produce availabilities that are higher than solid grids, where every position must be occupied by a node. In addition to proposing an improvement to the existing grid protocol, new insights are offered into the performance of the grids, from both availability and load sharing points of view. Algorithms for designing grids to maximize availability independently and also in conjunction with a load sharing constraint are given.<<ETX>>
59757838
Operating System Support for Data Management.
42238558
A crash recovery algorithm based on multiple logs that exploits parallelism
The paper describes an efficient algorithm for recovery based on multiple logs. The standard WAL algorithm is designed to work with a single log. Since each transaction is required to write a commit record to the log, it imposes limits on the maximum achievable throughput even if group commits are allowed. These limits are well below the needs of high transaction rate systems in airlines and in other areas. Another problem with a 'single log' algorithm is that the tail of the log is a 'hot spot' because of severe contention for it. It is shown that both these problems are solved by extending the write-ahead logging method into a multiple log algorithm which allows transactions to write to one of several logs, and also permits each log to perform checkpoints and I/O operations in parallel. A further advantage of multiple logs is that parallelism can be exploited at recovery time. An algorithm is outlined that speeds up recovery by scanning the multiple logs in parallel.<<ETX>>
7923805
A reference model for team-enabled workflow management systems
Abstract Today's workflow systems assume that each work item is executed by a single worker. From the viewpoint of the system, a worker with the proper qualifications selects a work item, executes the associated work, and reports the result. There is usually no support for teams, i.e., groups of people collaborating by jointly executing work items (e.g., the program committee of a conference, the management team of a company, a working group, and the board of directors). In this paper, we propose the addition of a team concept to today's workflow management systems. Clearly, this involves a marriage of workflow and groupware technology. To shed light on the introduction of teams, we extend the traditional organizational meta model with teams and propose a team-enabled workflow reference model. For this reference model and to express constraints with respect to the distribution of work to teams, we use object constraint language (OCL).
28468806
Space-code bloom filter for efficient per-flow traffic measurement
Per-flow traffic measurement is critical for usage accounting, traffic engineering, and anomaly detection. Previous methodologies are either based on random sampling (e.g., Cisco's NetFlow), which is inaccurate, or only account for the "elephants". We introduce a novel technique for measuring per-flow traffic approximately, for all flows regardless of their sizes, at very high-speed (say, OC768). The core of this technique is a novel data structure called space code bloom filter (SCBF). A SCBF is an approximate representation of a multiset; each element in this multiset is a traffic flow and its multiplicity is the number of packets in the flow. The multiplicity of an element in the multiset represented by SCBF can be estimated through either of two mechanisms-maximum likelihood estimation (MLE) or mean value estimation (MVE). Through parameter tuning, SCBF allows for graceful tradeoff between measurement accuracy and computational and storage complexity. SCBF also contributes to the foundation of data streaming by introducing a new paradigm called blind streaming. We evaluate the performance of SCBF through mathematical analysis and through experiments on packet traces gathered from a tier-1 ISP backbone. Our results demonstrate that SCBF achieves reasonable measurement accuracy with very low storage and computational complexity
43715944
Performance Analysis and Scheduling of Stochastic Fork-Join Jobs in a Multicomputer System
The authors model a parallel processing system comprising several homogeneous computers interconnected by a communication network. Jobs arriving to this system have a linear fork-join structure. Each fork of the job gives rise to a random number of tasks that can be processed independently on any of the computers. Since exact analysis of fork-join models is known to be intractable, the authors resort to obtaining analytical bounds to the mean job response time of the fork-join job. For jobs with a single fork-join and, probabilistic allocation of tasks of the job to the N processors, they obtain upper and lower bounds to the mean job response time. Upper bounds are obtained using the concept of associated random variables and are found to be a good approximation to the mean job response time. A simple lower bound is obtained by neglecting queueing delays. They also find two lower bounds that include queueing delays. For multiple fork-join jobs, they study an approximation based on associated random variables. Finally, two versions of the join-the-shortest-queue (JSQ) allocation policy (i.e., JSQ by batch and JSQ by task) are studied and compared, via simulations and diffusion limits. >
206590820
Structure from Motion with Known Camera Positions
The wide availability of GPS sensors is changing the landscape in the applications of structure from motion techniques for localization. In this paper, we study the problem of estimating camera orientations from multiple views, given the positions of the viewpoints in a world coordinate system and a set of point correspondences across the views. Given three or more views, the above problem has a finite number of solutions for three or more point correspondences. Given six or more views, the problem has a finite number of solutions for just two or more points. In the three-view case, we show the necessary and sufficient conditions for the three essential matrices to be consistent with a set of known baselines. We also introduce a method to recover the absolute orientations of three views in world coordinates from their essential matrices. To refine these estimates we perform a least-squares minimization on the group cross product SO(3) × SO(3) × SO(3). We report experiments on synthetic data and on data from the ICCV2005 Computer Vision Contest.
5053302
Componentxchange: An E-Exchange for Software Components
A key challenge in Component-Based Software Engineering (CBSE) is finding appropriate software components for reuse. A component broker that allows component vendors to make available their modules, and also allows component integrators to search and select components matching their requirements will help solve this problem. In this paper, we describe an E-Exchange for buying and selling of software components over the World Wide Web. The ComponentXchange uses an XML based specification language for components, which is a semi-formal specification language that can describe a rich and an extensible set of component properties including functional properties, non-functional attributes and licensing aspects. ComponentXchange supports two models of component trading. A component can be used either by downloading it and integrating it into the client application or by accessing it remotely over the network. It has a licensing server that enforces the licensing terms and conditions. ComponentXchange can be easily extended to support different payment models like pay-per-use, pay-per-user, etc.
8829443
Exploring the trade-off between label size and stack depth in MPLS routing
Multiprotocol label switching or MPLS technology is being increasingly deployed by several of the largest Internet service providers to solve problems such as traffic engineering and to offer IP services like virtual private networks (VPNs). In MPLS, the analysis of the packet (network layer) header is performed just once, and each packet is assigned a stack of labels, which is examined by subsequent routers when making forwarding decisions. Despite the fact that MPLS is becoming widespread on the Internet, we know essentially very little about the performance one can achieve with it, and about the intrinsic trade-offs in its use of resources. In this paper, we undertake a comprehensive study of the label size versus stack depth trade-off for MPLS routing protocols on lines and trees. We show that in addition to LSP tunneling, label stacks can also be used to dramatically reduce the number of labels required for setting up MPLS LSPs in a network. Based on this observation, we develop routing algorithms and prove lower bounds for two basic problems: (1) fixed label routing: given a fixed number of labels, we want to minimize the stack depth, and (2) fixed stack routing: given a bound on the stack depth, we want to minimize the number of labels used. Our simulation results validate our approach, demonstrating that our novel protocols enable MPLS routing on large trees with few labels and small stack sizes. Thus, our MPLS routing algorithms are applicable to a number of practical scenarios involving the provisioning of VPNs and multicast trees.