7450 2009-08-28 01:07:21 +0000 [XPath] 'for' expression example does not produce expected output 2010-02-17 22:56:28 +0000 1 1 1 Unclassified XPath / XQuery / XSLT XPath 2.0 Recommendation All All RESOLVED FIXED http://www.w3.org/TR/2007/REC-xpath20-20070123/#id-for-expressions P5 trivial --- 1 zongaro jonathan.robie public-qt-comments oldest_to_newest 26727 0 zongaro 2009-08-28 01:07:21 +0000 Some colleagues pointed out a problem in example 'for' expression that appears in the second box in section 3.7 of XPath 2.0.[1] for $a in fn:distinct-values(book/author) return (book/author[. = $a][1], book[author = $a]/title) The paragraph that appears before the example indicates that it "transforms the input document into a list in which each author's name appears only once, followed by a list of titles of books written by that author." However, the expression before the comma operator actually selects, for each book element that has one or more author elements that match $a, the first such author element for that book. So one author element will appear for each book written by that author. With the given input, the output will be: <author>Stevens</author> <author>Stevens</author> <title>TCP/IP Illustrated</title> <title>Advanced Programming in the Unix environment</title> <author>Abiteboul</author> <title>Data on the Web</title> <author>Buneman</author> <title>Data on the Web</title> <author>Suciu</author> <title>Data on the Web</title> The following was probably intended: for $a in fn:distinct-values(book/author) return ((book/author[. = $a])[1], book[author = $a]/title) The corresponding example in XQuery 1.0 was written differently, and does not have the same problem. [1] http://www.w3.org/TR/2007/REC-xpath20-20070123/#id-for-expressions 31743 1 jonathan.robie 2010-02-11 00:31:26 +0000 I am fixing this for future versions of XPath.