How can you specify co-dependent attributes in XSD?

[tskelly]

Hi,

Is there any way of specifying a pair of attributes that are both optional but if one is present the other must also be?

Thanks in advance.

[rski]

You can try to achieve this using abstract types and xsi:type attribute

xsd

<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.org/GolfCountryClub" xmlns:tns="http://www.example.org/GolfCountryClub">

	<element name="osoby">
		<complexType>
			<sequence>
				<element name="osoba" type="tns:tagType"></element>						
			</sequence>
		</complexType>
	</element>	
  
  
  
	<complexType name="tagType" abstract="true" />

	<complexType name="tagWithAttr">
   		<complexContent mixed="true">
      		<extension base="tns:tagType">
         		<attribute name="attr1" type="string" use="required"/>
         		<attribute name="attr2" type="string" use="required"/>
      		</extension>
   		</complexContent>
	</complexType>

	<complexType name="tagWithoutAttr">
   		<complexContent mixed="true">
      		<extension base="tns:tagType">
      		</extension>
   		</complexContent>
	</complexType>
</schema>

valid xmls

<?xml version="1.0" encoding="UTF-8"?>
<tns:osoby xmlns:tns="http://www.example.org/GolfCountryClub" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.example.org/GolfCountryClub GolfCountryClub.xsd ">
  <osoba attr1="18" attr2="19" xsi:type="tns:tagWithAttr"/>
</tns:osoby>

<?xml version="1.0" encoding="UTF-8"?>
<tns:osoby xmlns:tns="http://www.example.org/GolfCountryClub" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.example.org/GolfCountryClub GolfCountryClub.xsd ">
  <osoba xsi:type="tns:tagWithoutAttr"/>
</tns:osoby>

nonvalid xmls

<?xml version="1.0" encoding="UTF-8"?>
<tns:osoby xmlns:tns="http://www.example.org/GolfCountryClub" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.example.org/GolfCountryClub GolfCountryClub.xsd ">
  <osoba attr1="18"  xsi:type="tns:tagWithoutAttr"/>
</tns:osoby>

<?xml version="1.0" encoding="UTF-8"?>
<tns:osoby xmlns:tns="http://www.example.org/GolfCountryClub" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.example.org/GolfCountryClub GolfCountryClub.xsd ">
  <osoba attr1="18"  xsi:type="tns:tagWithAttr"/>
</tns:osoby>

Is that ok for you?

[tskelly]

Hi rski,

that's a good solution ... wish I had thought of it!!

However, we can't use it in this instance. We have written a system to process customer transmitted files conforming to a specific xsd that we provide. Our system is deployed and live and cannot be changed. This solution would require a code change.

Thanks though.

[rski]

Is it possible for you to add some Relax-NG formulas into the xsd file?