Stuttgart, University, Diss., 2003 (Nicht für den Austausch).

Berlin, Freie Universiẗat, Diss., 2000. / Dateiformat: zip, Dateien im PDF-Format.

Undergraduate honors paper--Mount Holyoke College, 2007. Dept. of Art. / Includes bibliographical references (leaf 12).

Universiẗat, Diss., 1999--Heidelberg.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M.A.)--Ohio State University, 1987. / Includes bibliographical references (leaves 77-79). Available online via OhioLINK's ETD Center

Proefschrift Universiteit van Amsterdam. / Met samenvatting in het Nederlands.

Workflow management systems enable organisations to deal with all aspects of business process management, including analysis, modelling, execution, and administration. Modelling workflow processes involves transformation of the process logic into a formal representation and it always remains a critical success factor for these systems. Workflow modelling languages provide constructs for capturing high-level descriptions of business processes, which are then have to be transformed and encoded into low-level execution semantics with the use of workflow programming languages. However, maintaining these models separately results in a number of issues, particularly when the various interdependencies between them are managed manually. This primarily creates difficulties in adaptation, in terms of identifying changes in high-level descriptions due to modifications of business conditions, and tracing the impact of those changes on the low-level execution semantics. Moreover, certain information included in the high-level descriptions is either partly encoded or omitted from the low-level execution semantics and at the same time, complicated business rules encoded at the execution level are not included in the high-level descriptions, creating major inconsistencies. The above issues result in high maintenance costs, reducing the overall efficiency and performance of workflow management systems. This thesis addresses the aforementioned problems by proposing a framework named SYMEX. SYMEX addresses the issue of integrating high and low-level descriptions in one unified format, from a Systems Theory perspective. SYMEX models have a mathematically defined formalism capable of capturing both high-level descriptions of business processes and low-level workflow execution semantics. Furthermore, SYMEX offers a concise and easy to learn and communicate set of constructs, allowing business analysts, process designers, and programmers to work on the same model, at different levels of abstraction. Apart from the theoretical framework, an XMLbased approach for the application of SYMEX is proposed, along with a constraint- based inference engine. Additionally, SYMEX models are evaluated in terms of their complexity and prove easier to read, understand, and manage than other traditional workflow modelling approaches. However, further research is required to assess the capability of the framework, with respect to modelling workflow processes in a service-oriented environment, where activities of business processes are essentially web-services exposed on the Internet.

The research conducted in this thesis is on distributed termination detection in multiagent systems. Agents engage in complex interactions by executing behaviour specifications in the form of protocols. This work presents and experiments with a framework for making termination in a multiagent system explicit. As a side effect, the mechanism can be exploited to aid management of agent interactions, by providing visibility of the interaction process and can be extended to drive multiagent system management tasks such as timely garbage collection. Results from previous attempts to deploy agents systems when scaling up, e.g. Agentcities, have shown and exposed a big gap between theory and practice especially in the reliability and availability of deployed systems. In particular more work needs to be done in the area of supporting agent infrastructures as much as in theoretical agent foundations. There are two aspects to this problem of termination detection in multiagent systems, firstly, the formal verification of behaviour at compile-time and secondly, monitoring and control at run-time. Regarding the former, there has been some work on the ver- 13 ification of agent communication languages. But overall verification is difficult and often requires knowledge of internal states of agents at compile time, and as yet has not been satisfactorily solved to be deployed in real systems. The second, the runtime approach is adopted in here. The research is not about protocol engineering but assumes correct protocols, and protocol specifications to be finite state machine graphs. Given these correct verified protocols, the thesis proposes a number of definitions culminating in identification of minimal information in the form of sub-protocols that agents being autonomous, can make available for the termination detection. An off line procedure for deriving these sub-protocols is then presented. The thesis then considers a termination detection model, and within this model, proposes an conversationmodel encompassing protocol executions, with hierarchical conversations modelled as diffusing computation trees and defines a number of predicates to derive termination in centralised and distributed environments. Algorithms that implement these predicates are sketched and some complexity analysis is performed. The thesis then considers a prototype implementation evaluated over some defined detection delays metric. The evaluation approach is heavily empirical, with an experimental approach adopted to evaluate various configurations of the termination detection mechanism. The evaluation employs robust resampling and bootstrapping methods to analyse and obtain distributions and confidence intervals of the detection delays metric for the termination detection mechanism.

Superconducting nanowire single photon detectors (SNSPDs) have emerged as mature detection technology that offers superior performance relative to competing infrared photon counting technologies. SNSPDs have the potential to revolutionize a range of advanced infrared photon counting applications, from quantum information science to remote sensing. The scale up to large area SNSPD arrays or cameras consisting of hundreds or thousands of pixels is limited by efficient readout schemes. This thesis gives a full overview of current SNSPD technology, describing design, fabrication, testing and applications. Prototype 4-pixel SNSPD arrays (30 x 30 µm2 and 60 x 60 µm2) were fabricated, tested and time-division multiplexed via a power combiner. In addition, a photon-number resolved code-division multiplexed 4-pixel array was simulated. Finally, a 100 m calibration-free distributed fibre temperature testbed, based on Raman backscattered photons detected by a single pixel fibre-coupled SNSPD housed in a Gifford McMahon cryostat was experimentally demonstrated with a spatial resolution of approximately 83 cm. At present, it is the longest range distributed thermometer based on SNSPD sensing.