Attribute Default Value

Hello,

     According to 3.4.5 "Complex Type Definition Information Set 
Contributions" of "XML Schema:  Structures" [1]

For each attribute use in the {attribute uses} whose {required} is false and whose {value constraint} is not ·absent· but whose {attribute declaration} does not match one of the attribute information items in the element 
information item's [attributes] as per clause 3.1 of Element Locally Valid (Complex Type) (§3.4.4) above, the post-schema-validation infoset has an attribute information 
item whose properties are as below added to the [attributes] of the element information item. 


The section goes on to list the properties for such an attribute 
information item as [local name], [namespace name], [schema normalized 
value], [schema default], [validation context], [validity], [validation 
attempted] and [schema specified].  In addition, such an attribute has 
[type definition] and [member type definition] properties as appropriate.

     Attribute information items, as described in 2.3 of "XML Information 
Set" [2], have the properties [namespace name], [local name], [prefix], 
[normalized value], [specified], [attribute type], [references] and [owner 
element].  The first two of these properties are mentioned for the 
attribute information items described by 3.4.5 of Structures, but what of 
the remaining six properties?

     The introduction of XML InfoSet Recommendation [3] states that some 
properties may have the value unknown or the value no value, which are distinct from all other values.  It's not clear whether each 
of the six properties of an attribute information item described in [2] 
but not mentioned in [1] has the value unknown, the value no value, or just isn't a property of such an attribute information item.

     If the six absent properties aren't actually properties of such an 
attribute information item, then I believe they should be described as 
some other kind of information item, rather than referring to the 
definition provided in the XML InfoSet Recommendation.

     If those six are properties of such an attribute information item, 
what values do they have?  It's not clear to me that the XML InfoSet 
Recommendation permits a property to have the special values unknown or no value, unless it explicitly indicates that a property could have one of those 
special values.  As I mentioned, [3] states that some properties may have 
those special values, but it doesn't state that every property may have 
such a special value.

Thanks,

Henry
[1] http://www.w3.org/TR/xmlschema-1/#section-Complex-Type-Definition-Information-Set-Contributions
[2] http://www.w3.org/TR/xml-infoset/#infoitem.attribute
[3] http://www.w3.org/TR/xml-infoset/#intro.null
------------------------------------------------------------------------
Henry Zongaro      XML Parsers development
IBM SWS Toronto Lab   Tie Line 969-6044;  Phone (905) 413-6044
mailto:zongaro@ca.ibm.com