11053365
Making Self-Adaptation an Engineering Reality
In this paper, we envision a world where a software engineer could take an existing software system, specify, for a set of properties of interest, an objective, conditions for change, and strategies for their adaptation and, within a few man weeks, make that system self-adaptive where it was not before. We describe how our approach generalizes to different classes of systems and holds promise for cost-effective, dynamic system self-adaptation to become an engineering reality.
1009077
An architecture for coordinating multiple self-management systems
A common approach to adding self-management capabilities to a system is to provide one or more external control modules, whose responsibility is to monitor system behavior, and adapt the system at run time to achieve various goals (configure the system, improve performance, recover from faults, etc.). An important problem arises when there is more than one such self-management module: how can one make sure that they are composed to provide consistent and complementary benefits? In this paper we describe a solution that introduces a self-management coordination architecture and infrastructure to support such composition. We focus on the problem of coordinating self-configuring and self-healing capabilities, particularly with respect to global configuration and incremental repair. We illustrate the approach in the context of a self-managing video teleconference system that composes two preexisting adaptation modules to achieve synergistic benefits of both.
9335785
Rainbow: architecture-based self-adaptation with reusable infrastructure
While attractive in principle, architecture-based self-adaptation raises a number of research and engineering challenges. First, the ability to handle a wide variety of systems must be addressed. Second, the need to reduce costs in adding external control to a system must be addressed. Our rainbow framework attempts to address both problems. By adopting an architecture-based approach, it provides reusable infrastructure together with mechanisms for specializing that infrastructure to the needs of specific systems. The specialization mechanisms let the developer of self-adaptation capabilities choose what aspects of the system to model and monitor, what conditions should trigger adaptation, and how to adapt the system.
8012254
Software architecture-based adaptation for Grid computing
Grid applications must increasingly self-adapt dynamically to changing environments. In most cases, adaptation has been implemented in an ad hoc fashion, on a per-application basis. This paper describes work which generalizes adaptation so that it can be used across applications by providing an adaptation framework. This framework uses a software architectural model of the system to analyze whether the application requires adaptation, and allows repairs to be written in the context of the architectural model and propagated to the running system. In this paper, we exemplify our framework by applying it to the domain of load-balancing a client-server system. We report on an experiment conducted using our framework, which illustrates that this approach maintains architectural requirements.
2936245
On failure recoverability of client-server applications in mobile wireless environments
Analytical results for the Cdf of the failure recovery time for client-server applications in mobile wireless environments characterized by logging, and mobility handoff strategies for facilitating failure recovery are reported in the paper. The results can be applied to determine if a mobile application can satisfy its recoverability requirement upon a mobile host failure when operating under a set of parameter values characterizing the mobile application, the underlying client-server environment, and the logging & mobility handoff strategies adopted by the mobile application. Model parameters which affect the shape of the failure recovery time Cdf for two mobility handoff strategies, namely, Eager and Lazy, are identified, and their effects are analyzed, with numerical data and result interpretations given. A tradeoff analysis between the cost invested by these two mobility handoff strategies for maintaining the logging and checkpoint information before failure versus the return of investment in terms of improved failure recoverability is given, and the best checkpoint interval period that would yield the best return of investment for the eager mobility handoff strategy over the lazy strategy is identified.
19385806
Lossy-to-lossless compression of medical volumetric data using three-dimensional integer wavelet transforms
We study lossy-to-lossless compression of medical volumetric data using three-dimensional (3-D) integer wavelet transforms. To achieve good lossy coding performance, it is important to have transforms that are unitary. In addition to the lifting approach, we first introduce a general 3-D integer wavelet packet transform structure that allows implicit bit shifting of wavelet coefficients to approximate a 3-D unitary transformation. We then focus on context modeling for efficient arithmetic coding of wavelet coefficients. Two state-of-the-art 3-D wavelet video coding techniques, namely, 3-D set partitioning in hierarchical trees (Kim et al., 2000) and 3-D embedded subband coding with optimal truncation (Xu et al., 2001), are modified and applied to compression of medical volumetric data, achieving the best performance published so far in the literature-both in terms of lossy and lossless compression.
30645069
Backtrack Routing and Priority-Based Wavelength Assignment in WDM Networks
In this paper, we consider two key problems in the WDM networks: the wavelengh assignment and routing problems. The objective of the problems is to minimize the request blocking rate. We propose two priority-based methods for the wavelength assignment problem: static and dynamic strategies. Based on the priority of an incoming request, the proposed methods allocate a wavelength among the available wavelengths for the given priority. Analytic models and simulations are presented for the proposed wavelength assignment methods so as to analyse the link blocking rate. The simulation results show that the link blocking rate by the dynamic strategy is less than that by the assignment strategy. We also develop a routing algorithm that works together with the proposed wavelength assignment methods to reduce the overall blocking rates. The proposed routing method maintains a routing tree for a given connection request. Based on the routing tree, the algorithm finds a route with one available wavelength for each link along the route. We compare the proposed routing method with the fixed routing and fixed alternate routing algorithms. The experiments show that the proposed routing algorithm performs better than the fixed routing and the alternate routing methods.
8458726
Approaching the largest β-skeleton within a minimum weight triangulation
Given a set S of n points in the plane, a triangulation is a maximal set of non-intersecting edges connecting the points in S. The weight of the triangulation is the sum of the lengths of the edges. The complexity of computing the minimum weight triangulation is currently unresolved. In this paper, we show that for ~ > 1/ sin K, the &skeleton of S is a subgraph of a minimum weight triangulation of S, where ~ = tan-1(3/m) N 7r/3.l. There exists a four point example such that the /3skeleton for ~ < 1/ sin(r/3) is not a subgraph of the minimum weight triangulation.
9588683
Performance evaluation of an admission control algorithm: dynamic threshold with negotiation
An admission control algorithm for a multimedia server is responsible for determining if a new request can be accepted without violating the QoS requirements of the existing requests in the system. Most admission control algorithms treat every request uniformly and hence optimize the system performance by maximizing the number of admitted and served requests. In practice, requests might have different levels of importance to the system. Requests offering high contribution or reward to the system performance deserve priority treatment. Failure of accepting a high-priority request would incur high penalty to the system.A novel threshold-based admission control algorithm with negotiation for two priority classes of requests is proposed in our previous study. The server capacity is divided into three partitions based on the threshold values: one for each class of requests and one common pool shared by two classes of requests. Reward and penalty are adopted in the proposed system model. High-priority requests are associated with higher values of reward as well as penalty than low-priority ones. In this paper, given the characteristics of the system workload, the proposed analytical models aim to finds the best partitions, optimizing the system performance based on the objective function of the total reward minus the total penalty. The negotiation mechanism reduces the QoS requirements of several low-priority clients, by cutting out a small fraction of the assigned server capacity, to accept a new high-priority client and to achieve a higher net earning value. Stochastic Petri-Net model is used to find the optimal threshold values and two analytical methods are developed to find sub-optimal settings. The experiment results show that the sub-optimal solutions found by the proposed analytical methods are very close to optimal ones. The methods enable the algorithm to dynamically adjust the threshold values, based on the characteristics of the system workload, to achieve higher system performance.