XML Schema

Name

xs:IDREFS — Definition of lists of references to unique identifiers.

Derived from:

xs:IDREF

Primary:

none

Known subtypes:

none

Facets:

xs:enumeration, xs:length, xs:maxLength, xs:minLength, xs:whiteSpace

<xs:simpleType name="IDREFS" id="IDREFS">
  <xs:restriction>
    <xs:simpleType>
      <xs:list>
        <xs:simpleType>
          <xs:restriction base="xs:IDREF"/>
        </xs:simpleType>
      </xs:list>
    </xs:simpleType>
    <xs:minLength value="1"/>
  </xs:restriction>
</xs:simpleType>

Description

xs:IDREFS is derived as a list from xs:IDREF and, thus, represents whitespace-separated lists of references to identifiers defined using the ID datatype.

The lexical space of xs:IDREFS is the lexical space of a list of xs:NCName values with a minimum length of one element (xs:IDREFS cannot be empty lists).

xs:IDREFS emulates the xs:IDREFS attribute type of the XML DTDs, even though it can be used to define simple content elements as well as attributes.

Restrictions

Applications that need to maintain a level of compatibility with DTDs should not use this datatype for elements but should reserve it for attributes.

The lexical domain (lists of xs:NCName) of this datatype doesn’t allow definition of lists of numerical key references or references containing whitespaces.

Although the W3C XML Schema provides another mechanism to define unique, key, and key reference constraints (using the xs:unique, xs:key, and xs:keyref elements) when more flexibility is needed, this mechanism doesn’t provide any alternative for lists of key references (similar ...