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.
2732754
A server side caching scheme for CORBA
We propose a caching scheme for saving the results of invocations of read methods at server side. Server side caching helps in reducing load on frequently accessed servers when computing the result is relatively costly. Our model provides strong consistency by using a dependency graph that specifies dependence information among method invocations of an object. We have implemented this scheme as a service in CORBA.
1888002
An Analysis and Taxonomy of Unstructured Workflows
Most workflow tools support structured workflows despite the fact that unstructured workflows can be more expressive. The reason for this is that unstructured workflows are more prone to errors. In this paper, we describe a taxonomy that serves as a framework for analyzing unstructured workflows. The taxonomy organizes unstructured workflows in terms of two considerations: improper nesting and mismatched split-join pairs. Based on this taxonomy we characterize situations that are well-behaved and others that are not. We also discuss well-behaved unstructured workflows that have equivalent structured mappings. Finally, we also introduce a relaxed notion of correctness called quasi-equivalence that is based on one-directional bisimulation. The results of our research will be useful for researchers investigating expressiveness and correctness issues in unstructured workflows.
5894333
Organizational modeling in UML and XML in the context of workflow systems
Workflow technology plays a key role as an enabler in E-Commerce applications, such as supply chains. Until recently the major share of the attention of workflow systems researchers has gone to the exchange of information in cross-organizational processes. Increasingly the focus is shifting from the exchange of data to support for interorganizational workflow processes. One of the initiatives in this direction has been XRL (eXchangeable Routing Language), an extendible instance-based language having an XML syntax and Petri-net semantics. In this paper, we move to the next level by extending XRL with organizational entities, structures, and rules. Hence, we describe an organizational model first in UML and then convert it into an XML DTD. Our organizational model allows for the specification of non-human resources, collections of resources (e.g., departments, teams, etc.), availability of resources, delegation, and role inheritance. Additional features of our proposal are the tight integration of organizational concepts and routing concepts. An important goal of this work is to create standard for organizational modeling much like the X. 500 standard for directories.
37821202
Optimizing Voting-Type Algorithms for Replicated Data
The main objectives of data replication are improved availability and reduced communications cost for queries. Maintaining the various copies consistent, however, increases the communications cost incurred by updates. For a given degree of replication, the choice of a specific concurrency control algorithm can have a significant impact on the total communications cost. In this paper we present various models for analyzing and understanding the trade-offs between the potentially opposing objectives of maximum resiliency and minimum communications cost in the context of the quorum consensus class of algorithms. It is argued that an optimal vote assignment is one which meets given resiliency goals and yet incurs the least communications cost compared with all other alternative assignments. A mathematical model for vote assignment is developed, and optimal algorithms are presented. It is demonstrated that significant cost savings can be realized from these approaches.
2753181
Hierarchical Quorum Consensus: A New Algorithm for Managing Replicated Data
A novel algorithm for managing replicated data is presented. The proposed method is based on organizing the copies of an object into a logical, multilevel hierarchy, and extending the quorum consensus algorithm to such an environment. Several properties of the method are derived and optimality conditions are given for minimizing the quorum size. It is shown that, given a collection of n copies of an object, the method allows a quorum to be formed with n/sup 0.63/ copies versus ((n+1)/2) copies in the case of the majority voting algorithm. Tradeoffs between the proposed method and three other quorum-based methods are discussed, and the main features of each method are highlighted. >
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.