xmlxsdschemaxml-attribute

Must ID attributes be unique in XML?

Having an XML document like this:

<Fathers>
  <Father ID="1">
    <Name>Homer</Name>
    <Sons>
       <Son ID="1">
           <Name>Bart</Name>
       </Son>
    </Sons>
  </Father>
</Fathers>

Is it valid to have the same attribute name ID in different nested tags?

Also, is it valid to have duplicate ID values?

Solution

  • ID attribute values must be unique in an XML document:

    Validity constraint: ID

    Values of type ID must match the Name production. A name must not appear more than once in an XML document as a value of this type; i.e., ID values must uniquely identify the elements which bear them.

    Regarding your other question, yes, it is ok to have the same attribute names, even ID, among nested elements.