CODEWITHSUNDEEP
xsdxml-validation
John K
John K

Reputation: 28869

XSD and element existence requirement, or other options

At the XSD level, can I define an element requirement based on presence of another element in the document?

For example, I want to require the element <firstname /> be provided whenever the <id /> element is also present, otherwise first name is optional.

If this cannot be enforced at the XSD level, then should I make both elements optional and enforce the requirement through a different level of checking?

Options welcome.

Upvotes: 1

Views: 357

Answers (2)

Daniel Haley
Daniel Haley

Reputation: 52858

Here's an example of this being done in a DTD. (Note: The test instances were validated using oXygen XML Editor (which is using Xerces).)

DTD (test.dtd)

<?xml version="1.0" encoding="UTF-8"?>
<!ELEMENT user ((firstname?|(firstname,id)),lastname)>
<!ELEMENT firstname (#PCDATA)>
<!ELEMENT lastname (#PCDATA)>
<!ELEMENT id (#PCDATA)>

Here are some example XML instances (valid and invalid):

Valid

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE user SYSTEM "test.dtd">
<user>
  <firstname/>
  <id/>
  <lastname/>
</user>

Invalid

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE user SYSTEM "test.dtd">
<user>
  <id/>
  <lastname/>
</user>

Valid

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE user SYSTEM "test.dtd">
<user>
  <firstname/>
  <lastname/>
</user>

Upvotes: 1

pmartin
pmartin

Reputation: 2741

This cannot be enforced at the XSD level.

Making both elements optional and enforcing the requirement at a different level in the application architecture sounds like a good option to me.

Upvotes: 1

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