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arXiv 1401.7388cs.LGmath.COstat.ML
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VC类到最大类的有界嵌入

Bounding Embeddings of VC Classes into Maximum Classes

The University of Melbourne(墨尔本大学);UC Berkeley(加州大学伯克利分校);Queensland University of Technology(昆士兰科技大学)

J. Hyam Rubinstein, Benjamin I. P. Rubinstein, Peter L. Bartlett

摘要:

计算学习理论中最早的理论之一--样本压缩理论--断言概念类(等价集合系统)在其VC维度上允许大小线性的压缩方案。到目前为止,这一说法是正确的最大类--那些拥有最大的基数为他们的VC维。最有前途的方法,积极解决的猜想是通过嵌入一般的VC类到最大类没有超线性增加的VC维度,因为这样的嵌入将扩展到所有的VC类的压缩方案。我们表明,最大类的特点是通过查看类作为一个立方复杂的图的局部连通性。最大VC类的这种几何特征被应用于证明一个否定的嵌入结果,该结果表明VC-d类不能嵌入到VC维低于2d的任何最大类中。另一方面,我们证明了每个VC-d类C嵌入到VC-(d+D)最大类中,其中D是C的亏数,即,最大VC-d类的基数与C的基数之间的差。对于VC-2类的二元n-立方体4 <= n <= 6,我们给出了最好的结果嵌入到最大类。对于一些特殊的布尔函数类,研究了它们与最大类的关系。最后给出了一个将VC-d类嵌入到VC-(d+k)极大类中的一般递归过程。

英文摘要:

One of the earliest conjectures in computational learning theory-the Sample Compression conjecture-asserts that concept classes (equivalently set systems) admit compression schemes of size linear in their VC dimension. To-date this statement is known to be true for maximum classes---those that possess maximum cardinality for their VC dimension. The most promising approach to positively resolving the conjecture is by embedding general VC classes into maximum classes without super-linear increase to their VC dimensions, as such embeddings would extend the known compression schemes to all VC classes. We show that maximum classes can be characterised by a local-connectivity property of the graph obtained by viewing the class as a cubical complex. This geometric characterisation of maximum VC classes is applied to prove a negative embedding result which demonstrates VC-d classes that cannot be embedded in any maximum class of VC dimension lower than 2d. On the other hand, we show that every VC-d class C embeds in a VC-(d+D) maximum class where D is the deficiency of C, i.e., the difference between the cardinalities of a maximum VC-d class and of C. For VC-2 classes in binary n-cubes for 4 <= n <= 6, we give best possible results on embedding into maximum classes. For some special classes of Boolean functions, relationships with maximum classes are investigated. Finally we give a general recursive procedure for embedding VC-d classes into VC-(d+k) maximum classes for smallest k.

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