We consider the problem of translating between irreducible closed sets and implicational bases in closure systems. To date, the complexity status of this problem is widely open, and it is further known to generalize the notorious hypergraph dualization problem, even in the context of acyclic convex geometries, i.e., closure systems admitting an acyclic implicational base. This paper studies this later class with a focus on the degree, which corresponds to the maximal number of implications in which an element occurs. We show that the problem is tractable for bounded values of this parameter, even when relaxed to the notions of premise- and conclusion-degree. Our algorithms rely on structural properties of acyclic convex geometries and involve various techniques from algorithmic enumeration such as solution graph traversal, saturation techniques, and a sequential approach leveraging from acyclicity. They are shown to perform in incremental-polynomial time. Finally, we complete these results by showing that our running times cannot be improved to polynomial delay using the standard framework of flashlight search.
翻译:本文研究闭包系统中不可约闭集与蕴含基之间的转换问题。迄今为止,该问题的复杂性状态尚未明确,且已知其可推广至著名的超图对偶化问题,即使在无环凸几何(即允许无环蕴含基的闭包系统)的背景下亦然。本文聚焦于此类系统中的度参数(对应元素在蕴含式中出现的最大次数)进行研究。我们证明当该参数有界时,即使放宽至前提度和结论度的概念,该问题仍具有可处理性。我们的算法基于无环凸几何的结构特性,并融合了算法枚举中的多种技术,包括解图遍历、饱和技术以及利用无环性的序列方法。这些算法被证明可在增量多项式时间内执行。最后,我们通过证明在标准手电筒搜索框架下无法将运行时间改进为多项式延迟,从而完善了上述结果。