http://www.logicmatters.net/2007/03/fixed-point-logics/ Logic, enthusiasms, sceptical thoughts, and a little LaTeX geekery Mon, 06 Feb 2012 19:23:02 +0000 hourly 1 http://wordpress.org/?v=3.1 http://www.logicmatters.net/2007/03/fixed-point-logics/comment-page-1/#comment-22 Peter Smith Sat, 10 Mar 2007 08:15:00 +0000 http://www.logicmatters.net/?p=57#comment-22 The ancestral <i>R*</i> of the relation <i>R</i> is that relation that stands to <i>R</i> as <i>ancestor of</i> stands to <i>parent of</i>. So <i>R*ak</i> is true just if there is a (finite) chain <i>a, b, c, ..., j, k</i> such that <i>Rab</i>, <i>Rbc</i>, <i>Rcd</i>, ..., <i>Rjk</i>. The ancestral R* of the relation R is that relation that stands to R as ancestor of stands to parent of. So R*ak is true just if there is a (finite) chain a, b, c, …, j, k such that Rab, Rbc, Rcd, …, Rjk.

]]> http://www.logicmatters.net/2007/03/fixed-point-logics/comment-page-1/#comment-21 Shawn Sat, 10 Mar 2007 02:11:00 +0000 http://www.logicmatters.net/?p=57#comment-21 This question might be a bit basic, but could you explain what an ancestral is? Googling turns up nothing of relevance, since the cognate 'ancestor' turns up too many genealogy sites. Thanks. This question might be a bit basic, but could you explain what an ancestral is? Googling turns up nothing of relevance, since the cognate ‘ancestor’ turns up too many genealogy sites. Thanks.

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