We study mobile systems, i.e. systems with a dynamically changing communication topology, from a process algebras point of view. Mobility can be introduced in process algebras by allowing names or terms to be transmitted. We distinguish these two approaches as first-order and higher-order. The major target of the thesis is the comparison between them. The prototypical calculus in the first-order paradigm is the π-calculus. By generalising its sort discipline we derive an w-order extension called Higher-Order π-calculus (HOπ). We show that such an extension does not add expressiveness to the π-calculus: Higher-order processes can be faithfully compiled down to first-order, and respecting the behavioural equivalence we adopted in the calculi. Such an equivalence is based on the notion of bisimulation, a fundamental concept of process algebras. Unfortunately, the standard definition of bisimulation is unsatisfactory in a higher-order calculus because it is over-discriminating. To overcome the problem, we propose barbed bisimulation. Its advantage is that it can be defined uniformly in different calculi because it only requires that the calculus possesses an interaction or reduction relation. As a test for barbed bisimulation, we show that in CCS and π-calculus, it allows us to recover the familiar bisimulation-based equivalences. We also give simpler characterisations of the equivalences utilised in HOπ. For this we exploit a special kind of agents called triggers, with which it is possible to reason fairly efficiently in a higher-order calculus notwithstanding the complexity of its transitions. Finally, we use the compilation from HOπ to π-calculus to investigate Milner's

by Wu Kam-wah. / Bibliography: leaves [129]-[130] / Thesis (M.Ph.)--Chinese University of Hong Kong, 1985

Programmers design, write, and understand programs with a high-level structure in mind. Existing programming languages are not very good at capturing this structure because they must include low-level implementation details. To address this problem we introduce Twig, a programming language that allows for domain-specific logic to be encoded alongside low-level functionality. Twig's language is based on a simple, formal calculus that is amenable to both human and machine reasoning. Users may introduce rules that rewrite expressions, allowing for user-defined optimizations. Twig can also incorporate procedures written in a variety of low-level languages. Our implementation supports C and Python, but our abstract model can accommodate other languages as well. We present Twig's design and formal semantics and discuss our implementation. We demonstrate Twig's use in two different domains, multi-language programming and GPU programming, and compare Twig against a well-known typemapping system, SWIG.

Digitized by Kansas Correctional Industries

<p>Streaming applications like multimedia and radar signal processing applications are becoming </p><p>increasingly compute-intensive. To overcome the computational demands new parallel </p><p>architectures are emerging. </p><p> </p><p>The programming tools provided with these architectures require low-level programming, which </p><p>creates a need for a common high-level architecture independent language that can exploit </p><p>parallelism efficiently. One such language is StreamIt, designed around the notions of streams </p><p>and stream transformers, which allows efficient mapping to a variety of architectures. </p><p> </p><p>The overall goal of this master’s thesis is to evaluate the StreamIt language from a </p><p>programmability and portability point of view. An MPD-application has been developed in </p><p>StreamIt, which is executed on the RAW simulator. Furthermore, a code generator is designed to </p><p>compile and execute the application on the XPP simulator. </p><p> </p><p>The conclusions drawn are that StreamIt is easy to learn, but hard to use because of its </p><p>programming paradigm as compared to conventional languages. StreamIt programming involves </p><p>thinking in terms of streams instead of globally accessed memory. The structure of StreamIt </p><p>makes it easy to reuse components and modify the application. The construction of the compiler </p><p>makes it possible to port StreamIt application to various architectures.</p>

Djang et al. [1998] introduced a new model of types for declarative visual programming languages (VPLs). Implicit static typing is used in their type model, in order to eliminate the programming mechanisms associated with type declarations, provide immediate visual feedback with respect to type errors and guarantee type safe programs. Their type model also evaluates types on a level of granularity that is finer than in previous approaches to types. Instead of evaluating types on the basis of abstract names, their model determines a set of operations that an object guarantees and compares this set to the set of operations this object is required to support. If the set of required operations is a subset of the set of guaranteed operations, then the object is considered type safe. This granularity provides their model with the ability to support inheritance without introducing explicit type declarations and to communicate type errors to users without requiring the user to understand a large set of terminology. These features of their model attempt to provide VPL users with more powerful programming capabilities without the introduction of a high learning curve. In this thesis, an implementation of the Djang et al.'s model of types is presented. Data structures and algorithms are developed that conform to the axioms prescribed by Djang et al. The space and time complexity analyses for our data structures and algorithms are examined. Our implementation provides new insights into the cost and performance of the Djang et al.'s type model. / Graduation date: 2000

We believe concreteness, direct manipulation and responsiveness in a visual programming language increase its usefulness. However, these characteristics present a challenge in generalizing programs for reuse, especially when concrete examples are used as one way of achieving concreteness. In this thesis, we present a technique to solve this problem by deriving generality automatically through the analysis of logical relationships among concrete program entities from the perspective of a particular computational goal. Use of this technique allows a fully general form-based program with reusable abstractions to be derived from one that was specified in terms of concrete examples and direct manipulation. Also addressed in this thesis is how to statically represent the generalized programs. In general, we address how to design better static representations. A weakness of many interactive visual programming languages is their static representations. Lack of an adequate static representation places a heavy cognitive burden on a VPL's programmers, because they must remember potentially long dynamic sequences of screen displays in order to understand a previously-written program. However, although this problem is widely acknowledged, research on how to design better static representations for interactive VPLs is still in its infancy. Building upon the cognitive dimensions developed for programming languages by cognitive psychologists Green and others, we have developed a set of concrete benchmarks for VPL designers to use when designing new static representations. These benchmarks provide design-time information that can be used to improve a VPL's static representation. / Graduation date: 1997

Streaming applications like multimedia and radar signal processing applications are becoming increasingly compute-intensive. To overcome the computational demands new parallel architectures are emerging.   The programming tools provided with these architectures require low-level programming, which creates a need for a common high-level architecture independent language that can exploit parallelism efficiently. One such language is StreamIt, designed around the notions of streams and stream transformers, which allows efficient mapping to a variety of architectures.   The overall goal of this master’s thesis is to evaluate the StreamIt language from a programmability and portability point of view. An MPD-application has been developed in StreamIt, which is executed on the RAW simulator. Furthermore, a code generator is designed to compile and execute the application on the XPP simulator.   The conclusions drawn are that StreamIt is easy to learn, but hard to use because of its programming paradigm as compared to conventional languages. StreamIt programming involves thinking in terms of streams instead of globally accessed memory. The structure of StreamIt makes it easy to reuse components and modify the application. The construction of the compiler makes it possible to port StreamIt application to various architectures.

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

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