IBM-DM-005: Lack of timezone property

Data Model Section 3.3.3 (Storing xs:dateTime, xs:date, and xs:time 
values): This section says that ". . . Implementations must keep track of 
both of these values . . .", meaning the date or time converted to UTC and 
a separate timezone expressed as a dayTimeDuration. But the definitions of 
element and attribute nodes do not provide any way to do this. The data 
model lists all the properties of each kind of node. The properties of an 
element node are base-uri, node-name, parent, type, children, attributes, 
namespaces, and nilled. None of these properties provide a way to store a 
separate timezone if the element contains an xs:time. If the data model 
requires some piece of information to be stored for an element or 
attribute node, then it must provide a property for this purpose. This is 
an example of the kind of problem that will be exposed by carefully 
specifying the types of the various node properties.