2148 2005-09-12 16:46:45 +0000 R-157: Question about non-deterministic content models 2009-04-21 19:25:05 +0000 1 1 1 Unclassified XML Schema Structures: XSD Part 1 1.0 only All All CLOSED WORKSFORME P2 normal --- 1 sandygao ht www-xml-schema-comments oldest_to_newest 6106 0 sandygao 2005-09-12 16:46:45 +0000 Despite the fact that multiple non-normative portions of the spec make it clear that ambiguous content-models were not intended to be allowed, the language used in the normative parts of xml-schema (structures) allows for ambiguous/non- deterministic content-models. The 'Unique Particle Attribution' constraint combined with section 3.8.4 _would_ require non-ambiguous content-models, were it not for the interaction of minOccurs/maxOccurs with these rules. There are 2 relatively simple fixes that I can think of: make it clear that minOccurs/maxOccurs are just syntactic sugar, and that the 'Unique Particle Attribution' constraint should not be impacted by this sugar. change section 3.8.4 to indicate that the partitioning of the content must be possible based only on the current position in the content-model and the name of the next element. (I.e. make it explicit that ambiguity is not allowed.) Here is an example: --- t.xsd <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" > <xs:element name="root"> <xs:complexType> <xs:sequence minOccurs="2" maxOccurs="2"> <xs:element name="a" minOccurs="2" maxOccurs = "unbounded"/> <xs:element name="b" minOccurs="0"/> </xs:sequence> </xs:complexType> </xs:element> </xs:schema> ---- t.xml <?xml version="1.0"?> <root><a/><a/><a/><a/><root> ---- t2.xml <?xml version="1.0"?> <root><a/><a/><a/><b/><a/><root> Both t.xml and t2.xml are valid according to the content-model, and in both cases there is unique particle attribution, but upon having parsed the 2nd and encountering the 3rd , it is impossible to know whether to start a new sub- sequence or to continue the current. For 1.xml, it is necessary to start a new sub-sequence at that point, and for t2.xml it is necessary to hold off. See the following for more info: http://lists.w3.org/Archives/Public/www-xml-schema-comments/2002AprJun/0129.html 6107 1 sandygao 2005-09-12 16:47:06 +0000 Response from Henry: http://lists.w3.org/Archives/Public/www-xml-schema-comments/2002AprJun/0139.html Resolution: Discussed at the Sept. 20 concall. RESOLVED: to classify R-157 as clarification without erratum.