30093 2017-04-17 11:58:50 +0000 [xslt30] Incorrect explanation of example pattern 2017-05-31 09:27:51 +0000 1 1 1 Unclassified XPath / XQuery / XSLT XSLT 3.0 Proposed Recommendation PC All CLOSED FIXED P2 normal --- 1 mike mike sca.w3c public-qt-comments oldest_to_newest 128540 0 mike 2017-04-17 11:58:50 +0000 In 5.5.1 we have an example pattern: //para matches any para element that has a parent node. This example is incorrect. The normative specification shows that this pattern matches any para element in a tree that is rooted at a document node. (This error is also present in the XSLT 2.0 specification.) 128573 1 mike 2017-05-04 17:43:07 +0000 The WG agreed the change, and I have changed the explanation of the example to say "//para matches any para element in a tree that is rooted at a document node". The WG also asked the editor, for the record, to provide a technical explanation of why the example is incorrect. The relevant rule for the semantics of this pattern is in §5.5.3 (The Meaning of a Pattern) and reads: an item N matches a pattern P if the following applies, where EE is the equivalent expression to P: N is a node, and the result of evaluating the expression root(.)//(EE) with a singleton focus based on N is a sequence that includes the node N So //para matches $N if the result of root($N)//(//para) contains N. This expression expands to root($N)/ descendant-or-self::node()/ ( root(.) treat as document-node()/ descendant-or-self::node()/ child::para ) If $X is a root node then for every descendant $D of $X, root($D) will be $X. So this can be simplified to root($N) treat as document-node()/ descendant-or-self::node()/ child::para It is clear that (a) all nodes selected by this expression are elements named para (b) in the case of a para for which root(.) is not a document node, the step (root(.) treat as document node) will fail with a dynamic error, and therefore the pattern will not match (c) for every element E in a tree that is rooted at a document node, E is either a child of the document node, or a child of a descendant of the document node, and therefore the pattern selects EVERY element named para in such a tree.