Optional AttributeGroup

I have to define a attribute grou开发者_Go百科p for 2 mutually inclusive data elements. In the below example if TO_DT is present FROM_DT has to be present and TO_DT is not present then FROM_DT is not present.

I thought of creating these as mandatory attributes and define attributegroup as optional but its not working:

<xs:attributeGroup name="DateRangeAttributes" id="Element_Common_545">
  <xs:attribute name="TO_DT" type="xs:date" use="required" id="Element_Common_547"/>
  <xs:attribute name="FROM_DT" type="xs:date" use="required" id="Element_Common_546"/>
<xs:attributeGroup>

Can anyone suggest a way to handle this using attributes

Sorry, that kind of constraint can't be enforced by XML Schema (1.0). You'll have a enforce it elsewhere (such as with code or XSLT) or change the format. Possibilities:

• Provide default values so both are effectively always present.
• Use a single attribute containing a length-2 list of dates.
• Use elements (you could also control the order, unlike attributes).

These constraints can be expressed in Schematron and in XML Schema 1.1.