开放全局约束的可收缩性
Contractibility for Open Global Constraints
摘要：
全局约束的开放形式允许在约束程序执行期间向参数添加新变量。这样的形式是需要困难的约束编程问题，其中问题的建设和问题的解决是交错的，并自然适合约束逻辑编程。但是，一般来说，当约束打开时，对于全局约束合理的过滤可能不合理。本文提供了一个简单的表征，称为收缩性，过滤仍然健全的约束时，约束是开放的。有了这个特性，我们就可以很容易地确定一个约束是否具有这个特性。在后一种情况下，我们可以用它来推导约束的可收缩近似。我们证明了这项工作的硬约束和软约束。在这个过程中，我们制定了两个一般类的软约束。
英文摘要：
Open forms of global constraints allow the addition of new variables to an argument during the execution of a constraint program. Such forms are needed for difficult constraint programming problems where problem construction and problem solving are interleaved, and fit naturally within constraint logic programming. However, in general, filtering that is sound for a global constraint can be unsound when the constraint is open. This paper provides a simple characterization, called contractibility, of the constraints where filtering remains sound when the constraint is open. With this characterization we can easily determine whether a constraint has this property or not. In the latter case, we can use it to derive a contractible approximation to the constraint. We demonstrate this work on both hard and soft constraints. In the process, we formulate two general classes of soft constraints.
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