1,029 research outputs found

    Undergraduate Catalog of Studies, 2023-2024

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    Graduate Catalog of Studies, 2023-2024

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    A Unifying Theory for Graph Transformation

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    The field of graph transformation studies the rule-based transformation of graphs. An important branch is the algebraic graph transformation tradition, in which approaches are defined and studied using the language of category theory. Most algebraic graph transformation approaches (such as DPO, SPO, SqPO, and AGREE) are opinionated about the local contexts that are allowed around matches for rules, and about how replacement in context should work exactly. The approaches also differ considerably in their underlying formal theories and their general expressiveness (e.g., not all frameworks allow duplication). This dissertation proposes an expressive algebraic graph transformation approach, called PBPO+, which is an adaptation of PBPO by Corradini et al. The central contribution is a proof that PBPO+ subsumes (under mild restrictions) DPO, SqPO, AGREE, and PBPO in the important categorical setting of quasitoposes. This result allows for a more unified study of graph transformation metatheory, methods, and tools. A concrete example of this is found in the second major contribution of this dissertation: a graph transformation termination method for PBPO+, based on decreasing interpretations, and defined for general categories. By applying the proposed encodings into PBPO+, this method can also be applied for DPO, SqPO, AGREE, and PBPO

    Undergraduate Catalog of Studies, 2023-2024

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    Graduate Catalog of Studies, 2023-2024

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    Formally verified animation for RoboChart using interaction trees

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    RoboChart is a core notation in the RoboStar framework. It is a timed and probabilistic domain-specific and state machine-based language for robotics. RoboChart supports shared variables and communication across entities in its component model. It has formal denotational semantics given in CSP. The semantic technique of Interaction Trees (ITrees) represents behaviours of reactive and concurrent programs interacting with their environments. Recent mechanisation of ITrees, ITree-based CSP semantics and a Z mathematical toolkit in Isabelle/HOL bring new applications of verification and animation for state-rich process languages, such as RoboChart. In this paper, we use ITrees to give RoboChart novel operational semantics, implement it in Isabelle, and use Isabelle’s code generator to generate verified and executable animations. We illustrate our approach using an autonomous chemical detector and patrol robot models, exhibiting nondeterminism and using shared variables. With animation, we show two concrete scenarios for the chemical detector when the robot encounters different environmental inputs and three for the patrol robot when its calibrated position is in other corridor sections. We also verify that the animated scenarios are trace refinements of the CSP denotational semantics of the RoboChart models using FDR, a refinement model checker for CSP. This ensures that our approach to resolve nondeterminism using CSP operators with priority is sound and correct

    LIPIcs, Volume 251, ITCS 2023, Complete Volume

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    LIPIcs, Volume 251, ITCS 2023, Complete Volum

    Undergraduate Catalog of Studies, 2022-2023

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    Farming out : a study.

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    Farming is one of severals ways of arranging for a group of individuals to perform work simultaneously. Farming is attractive. It is a simple concept, and yet it allocates work dynamically, balancing the load automatically. This gives rise to potentially great efficiency; yet the range of applications that can be farmed efficiently and which implementation strategies are the most effective has not been classified. This research has investigated the types of application, design and implementation that farm efficiently on computer systems constructed from a network of communicating parallel processors. This research shows that all applications can be farmed and identifies those concerns that dictate efficiency. For the first generation of transputer hardware, extensive experiments have been performed using Occam, independent of any specific application. This study identified the boundary conditions that dictate which design parameters farm efficiently. These boundary conditions are expressed in a general form that is directly amenable to other architectures. The specific quantitative results are of direct use to others who wish to implement farms on this architecture. Because of farming’s simplicity and potential for high efficiency, this work concludes that architects of parallel hardware should consider binding this paradigm into future systems so as to enable the dynamic allocation of processes to processors to take place automatically. As well as resulting in high levels of machine utilisation for all programs, this would also permanently remove the burden of allocation from the programmer
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