2554 2005-11-28 02:36:33 +0000 Should UPA be a model group or particle constraint? 2009-04-21 19:21:42 +0000 1 1 1 Unclassified XML Schema Structures: XSD Part 1 1.0/1.1 both All All CLOSED INVALID important, easy resolved P4 normal --- 1 sandygao cmsmcq www-xml-schema-comments oldest_to_newest 7275 0 sandygao 2005-11-28 02:36:38 +0000 Currently UPA is in 3.8.6 to constraint model groups. Consider the following: <complexType> <sequence maxOccurs="2"> <element name="a"/> <element name="a" minOccurs="0"/> </sequence> </complexType> This should be invalid, because for the input <a/><a/>, we don't know which element declaration to use for the second <a/>. The content type of this complex type is a particle, whose term is a model gruop (the only model group in the content type). This model group is a sequence of 2 element declarations. It's clear that the sequence model group itself doesn't violate UPA, then how do we flag this complex type as invalid? Shouldn't UPA be defined on particles? 11992 1 cmsmcq 2006-09-24 15:00:42 +0000 Strictly speaking, the Unique Particle Attribution constraint is described (both in 1.0 and in the status quo of 1.1) as applying to a 'content model', rather than a 'model group'. The term 'content model' is defined in section 2.2.3.2 as a particle: A particle can be used in a complex type definition to constrain the &#183;validation&#183; of the [children] of an element information item; such a particle is called a content model. In the example, the constraint applies to the particle whose term is the sequence, not to the sequence group itself. So the repetition information which is essential to detecting the problem is not lost. Does this sufficiently address the problem, or am I missing something? 12067 2 sandygao 2006-09-27 03:02:43 +0000 The analysis in comment #1 looks correct. I'm marking this bug as invalid. I obviously must have assumed the first 3 words of UPA to be "a model group" as opposed to "a content model". The confusion is probably caused by the fact that the constraint is in section "3.8.6 Model Groups".