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how far should you go with XML schema?

• From: "David Valera" <dvalera@p...>
• To: <xml-dev@x...>
• Date: Tue, 30 May 2000 09:53:26 +0200

hello,

Since I started the development of an XML schema for the XML documents I
will need to validate, I have been asking myself:

What are the limitations of XML schema if you compare them with RDMS
constraints?

I ask this because in the XML messages I have there are a few conditions
that cannot be expressed in XML schema. Just to ilustrate take the following
example:

<myroot>
	<married>yes</married>
	<dateofwedding>1973-10-12</dateofwedding>
</myroot>

I would love to have the possibility of having something like this in XML
schema: (look at the condition attributes in the dateofwedding element)

<xsd:element name="myroot">
 <xsd:complexType content="elementOnly">
  <xsd:element name="married">
   <xsd:simpleType base="xsd:string">
	<xsd:enumeration value="yes"/>
	<xsd:enumeration value="no"/>
   </xsd:simpleType>
  </xsd:element>
  <xsd:element name="dateofwedding"
    type="xsd:date" condition="if married=yes" then="minOccurs="0""
else="minOccurs="1"")/>
 </xsd:complexType>
</xsd:element>

"if married=yes" should of course be an xsl statement, but I hope you get
the point.

Is this a desirable development in XML schema? Will something like this be
implemented in future versions of XML schema? are there other XML drafts
that combine XML schema and lets say XSL do this kind of condition checking
during validation?

Thanks in advance for any thoughts on this...

David Valera


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