20643 2013-01-11 09:51:45 +0000 [XP3.0] Formal and informal definitions of derives-from() do not match 2013-06-19 10:07:10 +0000 1 1 1 Unclassified XPath / XQuery / XSLT XPath 3.0 Last Call drafts PC All CLOSED FIXED https://www.w3.org/Bugs/Public/show_bug.cgi?id=20632 P2 normal --- 1 mike jonathan.robie public-qt-comments oldest_to_newest 81225 0 mike 2013-01-11 09:51:45 +0000 This is transferred from the comment made by email here: https://lists.w3.org/Archives/Member/w3c-xsl-query/2013Jan/0003.html We say in 2.5.5 derives-from( AT, ET ) returns true if AT is derived from ET by restriction or extension, or if ET is a union type of which AT is a member type. If this were the case, then when a function expects union(xs:string, xs:decimal), it would be a type error to supply an xs:integer. Furthermore, "union type" should be "pure union type". This sentence is immediately followed by a paraphrase that says "formally, ...", and the paraphrase gives the a more complete definition. But there is no indication that the sentence quoted is to be regarded as incomplete or informal. A better definition might be: derives-from( AT, ET ) returns true if any of the following conditions applies: * AT is ET * ET is the base type of AT * ET is a pure union type of which AT is a member type * There is a type MT such that derives-from(AT, MT) and derives-from(MT, ET) The problem is exemplified by test instanceof138. The expected result for this test assumes that restrictedDate is substitutable for a union type that includes the base type of restrictedDate as one of its members. 81953 1 jonathan.robie 2013-01-22 17:34:36 +0000 The Working Group accepted the proposed change.