Table of contents

Appendices

3.5 AttributeUses

An attribute use is a utility component which controls the occurrence and defaulting behavior of attribute declarations. It plays the same role for attribute declarations in complex types that particles play for element declarations.

NOTE: 

<xs:complexType>
 . . .
 <xs:attribute ref="xml:lang" use="required"/>
 <xs:attribute ref="xml:space" default="preserve"/>
 <xs:attribute name="version" type="xs:number" fixed="1.0"/>
</xs:complexType>
     

XML representations which all involve attribute uses, illustrating some of the possibilities for controlling occurrence.

The Attribute Use Schema Component[top]

The attribute use schema component has the following properties:

[required] determines whether this use of an attribute declaration requires an appropriate attribute information item to be present, or merely allows it.

[attribute] provides the attribute declaration itself, which will in turn determine the simple type definition used.

[au-value_constraint] allows for local specification of a default or fixed value. This must be consistent with that of the [attribute], in that if the [attribute] specifies a fixed value, the only allowed [au-value_constraint] is the same fixed value.

XML Representation of Attribute Use Components[top]

Attribute uses correspond to all uses of [attribute] which allow a use attribute. These in turn correspond to two components in each case, an attribute use and its [attribute] (although note the latter is not new when the attribute use is a reference to a top-level attribute declaration). The appropriate mapping is described in [XML Representation of Attribute Declaration Schema Components].

Constraints on XML Representations of Attribute Uses[top]

None as such.

Attribute Use Validation Rules[top]

For an attribute information item to bevalid with respect to an attribute use its normalized value must match the canonical lexical representation of the attribute use's [au-value_constraint] value, if it is present and fixed.

Attribute Use Information Set Contributions[top]

None as such.

Constraints on Attribute Use Schema Components[top]

All attribute uses (see [AttributeUses]) must satisfy the following constraints.

1. The values of the properties of an attribute use must be as described in the property tableau in [The Attribute Use Schema Component], modulo the impact of [Missing Sub-components].

2. If the [attribute] has a fixed [a-value_constraint], then if the attribute use itself has a [au-value_constraint], it must also be fixed and its value must match that of the [attribute]'s [a-value_constraint].