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  • 1.
    Bevemyr, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Computing Science Department.
    Data-parallel Implementation of Prolog1996Doctoral thesis, comprehensive summary (Other academic)
  • 2.
    Dell'Acqua, Pierangelo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Computing Science Department.
    Reflection Principles in Computational Logic1998Doctoral thesis, monograph (Other academic)
    Abstract [en]

    We introduce the concept of reflection principles as a knowledge representation paradigm in a computational logic setting. Reflection principles are expressed as certain kinds of logic schemata intended to capture the basic properties of the domain knowledge to be modelled. Reflection is then used to instantiate these schemata to answer specific queries about the domain.

    This differs from other approaches to reflection mainly in the following three ways. First, it uses logical instead of procedural reflection. Second, it aims at a cognitively adequate declarative representation of various forms of knowledge and reasoning, as opposed to reflection as a means for controlling computation or deduction. Third, it facilitates the building of a complex theory by allowing a simpler theory to be enhanced by a compact metatheory, contrary to the construction of metatheories that are only conservative extensions of the basic theory.

    A computational logic system for embedding reflection principles, called RCL (for Reflective Computational Logic), is presented in full detail. The system is an extension of Horn clause resolution-based logic, and is devised in a way that makes important features of reflection parametric as much as possible, so that they can be tailored according to specific needs of different application domains. Declarative and procedural semantics of the logic are described and correctness and completeness of reflection as logical inference are proved. Examples of reflection principles for three different application areas are shown.

    The proposed approach to reflection is powerful and flexible enough to be integrated into different frameworks. We show how the use of reflection principles can be integrated into a framework of rational, reactive agents to enhance their reasoning capabilities. Finally, relationship with a variety of distinct sources within the literature on relevant topics is discussed.

  • 3.
    Hjerpe, Torkel
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Computing Science Department.
    High-level specification and efficient solving of constraint satisfaction problems1995Doctoral thesis, comprehensive summary (Other academic)
  • 4.
    Lindgren, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Computing Science Department.
    Compilation Techniques for Prolog1996Doctoral thesis, comprehensive summary (Other academic)
  • 5.
    Mildner, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Computing Science Department.
    Type Domains for Abstract Interpretation: A critical study1999Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Programming languages with dynamic typing such as Prolog do not require that the programmer declares the types of data or procedures. This flexibility, however, comes at a price. The lack of declarations makes it hard for a compiler to produce fast code since data must be assumed to be of any type.

    Abstract interpretation is a technique to automatically infer conservative approximations of program properties such as the types of program variables and procedure arguments. The properties of interest are described using an abstract domain. The abstract domains for type analysis investigated in this thesis are based on deterministic term grammars but differ in the representation of the term grammars and in the widening used, that is, the method used to ensure that the analysis terminates.

    One proposed representation of term grammars, type graphs, are shown to be exponentially larger than the term grammars they represent not only in the worst case but also in practice. One previously proposed widening for type graphs is shown to be impractically expensive and also no more precise than other more efficient methods. A novel implementation technique is proposed for another type graph widening that appears in the literature. The precision using this implementation technique is shown to be better than for the other investigated widenings. The performance, however, suffers from the problems inherent in the type graph representation unless some crucial modifications to the analyzer are made.

    To overcome the problems with the type graph representation a more compact representation of term grammars is proposed. A number of widenings using this representation are investigated and shown not to suffer from problems with huge term grammar representations. The precision obtained using these widenings are as good or better than the precision obtained using the original widening proposed for type graphs.

    Finally, two sets of benchmarks that have been used in the literature to investigate analysis methods are considered. It is shown that these benchmarks will give unrealistically good absolute precision and one set of benchmarks, the GAIA benchmarks, is shown to have further deficiencies that make it completely unsuitable for benchmarking purposes.

  • 6.
    Montelius, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Computing Science Department. Swedish Institute of Computer Science.
    Exploiting Fine-grain Parallelism in Concurrent Constraint Languages1997Doctoral thesis, monograph (Other academic)
  • 7.
    Nyström, Sven-Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Computing Science Department.
    Denotational Semantics for Asynchronous Concurrent Languages1996Doctoral thesis, monograph (Other academic)
  • 8.
    Veanes, Margus
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Computing Science Department.
    On Simultaneous Rigid E-Unification1997Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Automated theorem proving methods in classical logic with equality that are based on the Herbrand theorem, reduce to a problem called Simultaneous Rigid E-Unification, or SREU for short. Recent developments show that SREU has also close connections with intuitionistic logic with equality, second-order unification, some combinatorial problems and finite tree automata.

    We show new decidability results of various cases of SREU. In particular, we improve upon the undecidability result of SREU by showing its undecidability in a very restricted case, in fact the minimal known case. We prove the decidability of some cases of SREU under certain restrictions regarding the number of variables and other syntactical criteria. To prove the (computational) complexity of some cases, we reduce them to certain decision problems of finite tree automata. The complexity of the latter problems is studied first. In connection with that, we present a survey of closely related problems and give a comparison with the corresponding results in classical automata theory.

    These results are applied in the context of intuitionistic logic with equality, to obtain a complete classification of its prenex fragment in terms of the quantifier prefix: the ∃∃-fragment is shown undecidable and the ∀*∃∀*-fragment is shown decidable. These results have further implications for proof search in intuitionistic logic with equality.

    We also improve upon a number of other recent undecidability results that are related to the so-called Herbrand Skeleton problem and are of fundamental importance in automated theorem proving in in classical logic with equality. In that context we also prove, as our main tool, a logical theorem that we believe is of independent interest.

  • 9.
    Veanes, Margus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Computing Science Department.
    Barklund, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Computing Science Department.
    Natural cycletrees: Flexible interconnection graphs1996In: Journal of Parallel and Distributed Computing, ISSN 0743-7315, E-ISSN 1096-0848, Vol. 33, no 1, p. 44-54Article in journal (Refereed)
    Abstract [en]

    Natural cycletrees, formally defined in this paper, is a subclass of Hamiltonian graphs with maximum degree 3 that contain a binary spanning tree. A natural cycletree used as an interconnection network thus supports directly broadcasting through the binary tree as well as nearest-neighbor communication through the cycle. Natural cycletrees have several other interesting properties; e.g., they are planar, easily extensible, and can be contracted using the same methods as for binary trees. The main results of the paper are: (i) Given an arbitrary basic binary spanning treeT, there exists a natural cycletree with a minimal number of edges forT. (ii) A natural cycletree has a very simple router. We give a superfast parallel algorithm that can establish near optimal router data for that router.

  • 10.
    Veanes, Margus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Computing Science Department.
    Barklund, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Computing Science Department.
    On the number of edges in cycletrees1996In: Information Processing Letters, ISSN 0020-0190, E-ISSN 1872-6119, Vol. 57, no 4, p. 225-229Article in journal (Refereed)
    Abstract [en]

    Given N vertices v1,…, vn, how many edges does it take to form a graph that contains a Hamiltonian cycle (v1, v2,…, vN, v1) and a basic binary spanning tree with some vertex vr as root? In this article the question is answered exactly — the answer is approximately . Moreover, it is shown that for any odd N there exists a natural cycletree with N vertices, a minimal number of edges and a minimal total path length.

1 - 10 of 10
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