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This thesis considers several instances of abstraction that arose in the design and implementation of the web programming language Links. The first concerns user interfaces, specified using HTML forms. We wish to construct forms from existing form fragments without introducing dependencies on the implementation details of those fragments. Surprisingly, many existing web systems do not support this simple scenario. We present a library which captures the essence of form abstraction, and extend it with more practical facilities, such as validation of the HTML a program produces and of the input a user submits. An important part of our library is a simple semantics, given as the composition of three primitive “idioms”, an interface to computation introduced by McBride and Paterson. In order to justify this approach we present a comparison of idioms with the related notions of monads and arrows, refining the informal claims in the literature. Our library forms part of the Links framework for stateless web interactions. We describe a related aspect of this system, a preprocessor that derives generic instances of functions, which we use to serialise server state between client requests. The abstraction in this case involves the shape of datatypes: the serialisation operation is specified independently of the particular types involved. Our final instance of abstraction involves abstract types. Functional programming languages typically offer one of two styles of abstract type: the abstraction boundary may be drawn using a private data constructor, or using a type signature. We show that there is a pair of semantics-preserving translations between these two styles. In the light of this, we revisit the decision of the Haskell designers to offer the constructor style, and define a library that supports signature-style definitions in Haskell by translation into the constructor style.

This dissertation reports the results of research into the provision of adaptive user interfaces to support individuals in the management of their personal information. Many individuals find that they have increased responsibility for managing aspects of their own lives, including the information associated with their jobs. In contrast with traditional approaches to information management, which are generally driven by organisational or business requirements, the requirements of personal information management systems tend to be less rigidly defined. This dissertation employs research from the areas of personal information management and adaptive user interfaces - systems which can monitor how they are used, and adapt on a personal level to their user - to address some of the particular requirements of personal information management systems. An adaptive user interface can be implemented using a variety of techniques, and this dissertation draws on research from the area of software agents to suggest that reactive software agents can be fruitfully applied to realise the required adaptivity. The reactive approach is then used in the specification and development of an adaptive interface which supports simple elements of personal information management tasks. The resulting application is evaluated by means of user trials and a usability inspection, and the theoretical architectures and techniques used in the specification and development of the software are critically appraised. The dissertation demonstrates an application of reactive software agents in adaptive systems design and shows how the behaviour of the system can be specified based on the analysis of some representative personal information management tasks.

The channel flow method has established the net dissolution kinetics of calcite single crystals at high pH (7.7-9.7) and varying bulk Ca²⁺ concentrations (0-10 mM), using wide ranges of solution flow rates (10^-3-0.3 cm³ s^-1). Literature rate equations were in poor agreement with experiment. Modelling with the following mechanism, where Ca²⁺ and CO₃^2- undergo Langmuirian adsorption: Ca²⁺_(aq) ⇄ Ca²⁺_(ads) CO^2-</sub>3 (aq)</sub> ⇄ CO^2-_{3 (ads)} Ca(sup>2+</sup></sub>(ads)</sub> + CO^2-_{3 (ads)} ⇄ CaCO_{3 (ads)} CaCo_{3 (ads)} → CaCo_{3 (lattice)} and the consequent rate law J_net/mol cm<sup>-2</sub>s^-1 = k_pK_CaK_CO₃ {K_sp - [Ca²⁺]_o[CO^2-₃]_o (1 + K_Ca[Ca²⁺]_o)(1 + K<sub>CO₃[CO^2-₃]_o) gave excellent agreement with experiment under all conditions studied. This mechanism is shown to explain all literature streaming potential, electrophoresis and kinetic salt effect data. Dissolution of calcite under the above conditions was strongly inhibited by Mg²⁺ and fully deprotonated forms of succinic acid, 2-sulphobutanedioic acid, phthalic acid and maleic acid. Mechanisms were established; for the maleate dianion, the inhibition was due to the blocking of the dissolution sites at which CaCO₃ units are incorporated into the crystal lattice. For the other ions, inhibition arose from competitive Langmuirian adsorption either between CO₃<sup>2-<sup> and the anions, or between Ca²⁺ and Mg²⁺. A new method to quantify the inhibited dissolution of particulate CaCO₃ (=10 μm) via enhanced mass transport of solution to the rotating disc electrode, due to the rotation of the particles in the diffusion layer, has been established. Good agreement was found with that measured independently using the channel flow cell. A.c. impedance spectroscopy has been used to characterise scaled (CaCO₃) steel tubes. Results provide scope for (i) monitoring scale growth, and (ii) use in safety control devices for alerting to the scaling of pipe-work.