23,563 research outputs found

    Sketched Answer Set Programming

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    Answer Set Programming (ASP) is a powerful modeling formalism for combinatorial problems. However, writing ASP models is not trivial. We propose a novel method, called Sketched Answer Set Programming (SkASP), aiming at supporting the user in resolving this issue. The user writes an ASP program while marking uncertain parts open with question marks. In addition, the user provides a number of positive and negative examples of the desired program behaviour. The sketched model is rewritten into another ASP program, which is solved by traditional methods. As a result, the user obtains a functional and reusable ASP program modelling her problem. We evaluate our approach on 21 well known puzzles and combinatorial problems inspired by Karp's 21 NP-complete problems and demonstrate a use-case for a database application based on ASP.Comment: 15 pages, 11 figures; to appear in ICTAI 201

    Breaking Instance-Independent Symmetries In Exact Graph Coloring

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    Code optimization and high level synthesis can be posed as constraint satisfaction and optimization problems, such as graph coloring used in register allocation. Graph coloring is also used to model more traditional CSPs relevant to AI, such as planning, time-tabling and scheduling. Provably optimal solutions may be desirable for commercial and defense applications. Additionally, for applications such as register allocation and code optimization, naturally-occurring instances of graph coloring are often small and can be solved optimally. A recent wave of improvements in algorithms for Boolean satisfiability (SAT) and 0-1 Integer Linear Programming (ILP) suggests generic problem-reduction methods, rather than problem-specific heuristics, because (1) heuristics may be upset by new constraints, (2) heuristics tend to ignore structure, and (3) many relevant problems are provably inapproximable. Problem reductions often lead to highly symmetric SAT instances, and symmetries are known to slow down SAT solvers. In this work, we compare several avenues for symmetry breaking, in particular when certain kinds of symmetry are present in all generated instances. Our focus on reducing CSPs to SAT allows us to leverage recent dramatic improvement in SAT solvers and automatically benefit from future progress. We can use a variety of black-box SAT solvers without modifying their source code because our symmetry-breaking techniques are static, i.e., we detect symmetries and add symmetry breaking predicates (SBPs) during pre-processing. An important result of our work is that among the types of instance-independent SBPs we studied and their combinations, the simplest and least complete constructions are the most effective. Our experiments also clearly indicate that instance-independent symmetries should mostly be processed together with instance-specific symmetries rather than at the specification level, contrary to what has been suggested in the literature

    A reusable iterative optimization software library to solve combinatorial problems with approximate reasoning

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    Real world combinatorial optimization problems such as scheduling are typically too complex to solve with exact methods. Additionally, the problems often have to observe vaguely specified constraints of different importance, the available data may be uncertain, and compromises between antagonistic criteria may be necessary. We present a combination of approximate reasoning based constraints and iterative optimization based heuristics that help to model and solve such problems in a framework of C++ software libraries called StarFLIP++. While initially developed to schedule continuous caster units in steel plants, we present in this paper results from reusing the library components in a shift scheduling system for the workforce of an industrial production plant.Comment: 33 pages, 9 figures; for a project overview see http://www.dbai.tuwien.ac.at/proj/StarFLIP

    Working Notes from the 1992 AAAI Spring Symposium on Practical Approaches to Scheduling and Planning

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    The symposium presented issues involved in the development of scheduling systems that can deal with resource and time limitations. To qualify, a system must be implemented and tested to some degree on non-trivial problems (ideally, on real-world problems). However, a system need not be fully deployed to qualify. Systems that schedule actions in terms of metric time constraints typically represent and reason about an external numeric clock or calendar and can be contrasted with those systems that represent time purely symbolically. The following topics are discussed: integrating planning and scheduling; integrating symbolic goals and numerical utilities; managing uncertainty; incremental rescheduling; managing limited computation time; anytime scheduling and planning algorithms, systems; dependency analysis and schedule reuse; management of schedule and plan execution; and incorporation of discrete event techniques

    Representation-Selection for Constraint Satisfaction Problems: A Case Study Using n-Queens

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    https://deepblue.lib.umich.edu/bitstream/2027.42/154179/1/39015100081804.pd

    Universalization or localization? Issues of knowledge legitimation in comaprative education

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    The endeavor to unite the universal and the accidental in both, the physical and the social world into one theoretical framework – the idea of such a unity can be found already in the Chinese concept of Tao – dates back in the modern culture to the Enlightenment. Such a unified knowledge came to be understood as a potential tool of forecasting and controlling societal progress. All through the positivistic 19th century, comparativists followed Marc-Antoine Jullien de Paris, who thought educational comparison should become an exact science whose outcomes could be used anywhere and transplanted to any place. It was Michael Sadler who as the first comparative educationalist strictly refused the idea of cultural and institutional borrowing. Under his influence comparative education focused on the variations unique to the single countries and to the factors underlying these variations. Even the later emerging functionalist method remained in the tradition of a „one-dimensional logic“, which, as Marcuse alleged, was inseparably connected with the rationale of domination of nature and society. It is only the postmodern sight, which – without giving up the humanistic ideas of modernity which originated in Western modernization – opens possibilities to enter a cross cultural dialogue and to accept multiple theoretical realities. (DIPF/Orig.)Der Beitrag bietet einen breiten Überblick über grundlegende Tendenzen in der historischen Entwicklung von Vergleichender Erziehungswissenschaft. Dabei unterliegt der Darstellung implizit und explizit durchgängig das Bewußtsein, daß vergleichende Wissenschaft im weitesten Sinne weder ein Monopol der jüngsten Epoche noch etwa eines einzigen Kulturraums darstellt. Mit seiner analytischen, aber auch normativen Interpretation von gegenwärtigen Tendenzen postmodernen Denkens sieht er die Möglichkeit eines transkulturellen Dialogs über die Weiterentwicklung und Erweiterung der etablierten (westlichen) Vergleichenden (Erziehungs-)Wissenschaft. (DIPF/Orig.
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