Question

is it possible in XML Schema to define the same element with several different definitions depending on one attribute.

As Example:

<xsd:element name="Element">
  <xsd:complexType>
    <xsd:sequence>
     <xsd:attribute name="type" fixed="type1"/>
    <xsd:seqeuence>
  </xsd:complexType>
</xsd:element>

<xsd:element name="Element">
  <xsd:complexType>
    <xsd:sequence>
     <xsd:attribute name="type" fixed="type2"/>
     <xsd:attribute name="value" type="xsd:integer"/>
    <xsd:seqeuence>
  </xsd:complexType>
</xsd:element>

<xsd:element name="RootElement">
  <xsd:complexType>
    <xsd:sequence>
     <xsd:element ref="Element"/>
    </xsd:sequence>
  </xsd:complexType>
</xsd:element>

Or is there any other way to solve this problem.
It is important that both definitions are named “Element”, because I have an application needing that both elements are named the same way. But there is a second application that needs the additional information for type2.

Answer 1

Consider removing the type attribute and just defining two childnodes with the different structures you wish.

This way you can have

<Element>
  <ElementType1>
    <!--whatever-->
  </ElementType1>
</Element>

and

<Element>
  <ElementType2 value="42">
    <!--whatever-->
  </ElementType1>
</Element>

in the same document.

Try this in the DTD section for Element:

<!ELEMENT Element (ElementType1?)>  <!-- the ? means 1 or 0 -->
<!ELEMENT Element (ElementType2?)>  

or rather this if only one is ever allowed under Element and Element is not allowed to be empty:

<!ELEMENT Element (ElementType1 | ElementType1)>

You can read more on about DTD element operators.