this paper, we look at database middleware systems as tranformation engines, and discuss when and how data is transformed to provide users with the information they need.

I declare that this thesis is my own account of my research and contains as its main content work which has not previously been submitted for a degree at any tertiary education institution.

April 29, 2011Für UnsShe had never before seen a rabbit with either a waistcoat-pocket, or a watch to take out of it, and burning with curiosity, she ran across the field after it Lewis CarrollThe following document, written under the supervision of Dr. reviewed by:

This thesis presents CraneTracker, a multi-modal sensing and communication system for monitoring migratory species at the continental level. By exploiting the robust and extensive cellular infrastructure across the continent, traditional mobile wireless sensor networks can be extended to enable reliable, low-cost monitoring of migratory species. The developed multi-tier architecture yields ecologists with unconventional behavior in-formation not furnished by alternative tracking systems at such a large scale and for a low-cost. The simulation, development and implementation of the CraneTracker soft-ware system is presented. The system is shown effective through multiple proxy deploy-

Hiermit versichere ich, die vorliegende Master-Thesis ohne Hilfe Dritter nur mit den angegebenen Quellen und Hilfsmitteln angefertigt zu haben. Alle Stellen, die aus Quellen entnommen wurden, sind als solche kenntlich gemacht. Diese Arbeit hat in gleicher oder ähnlicher Form noch keiner Prüfungsbehörde vorgelegen. Darmstadt, den 17. Mai 2011 (Marcel Lucas) The popularity of Networked Virtual Environments (NVE) increased remarkably in recent years where a plethora of players participate concurrently. Traditional approaches applying the Client/Server pattern swiftly reach their limit in terms of scalability and maintainability. Hence, different approaches are based on Peer-to-Peer (P2P) technology. In particular, fast-paced NVEs stress these systems and most likely cause high overlay maintenance overhead. This Master’s Thesis presents a novel approach to spatial Publish/Subscribe (Pub/Sub) in P2P NVEs. The unstructured P2P system BubbleStorm offers flexible and scalable means and is therefore used as a fundamental base for the developed Pub/Sub system. As the evaluation of the subscription is performed

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Abstract — J2EE applications are becoming increasingly ubiquitous and with their increasing adoption, performance and scalability issues are gaining in importance. For a J2EE application to perform well and be scalable, both the platform on which it is built and the application design must be efficient and scalable. Industry-standard benchmarks such as the SPECjAppServer set of benchmarks help to evaluate the performance and scalability of alternative platforms for J2EE applications, however, they cannot be used to evaluate the performance and scalability of concrete applications built on the selected platforms. In this paper, we present a systematic approach for evaluating and predicting the performance and scalability of J2EE applications based on modeling and simulation. The approach helps to identify and eliminate bottlenecks in the application design and ensure that systems are designed and sized to meet their quality of service requirements. We introduce our approach by showing how it can be applied to the SPECjAppServer2004 benchmark which is used as a representative J2EE application. A detailed model of a SPECjAppServer2004 deployment is built in a step-by-step fashion and then used to predict the behavior of the system under load. The approach is validated by comparing model predictions against measurements on the real system. Index Terms — Performance modeling and prediction, software verification, performance evaluation, distributed systems

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