[oXygen-user] XML Schema and empty elements

[George Cristian Bina]

Hi Timothy,

Thanks for the note, however, do you mind if you share with the rest of 
us your solution?

The nillable flag if disabled by default. If set it specifies that an 
element can have no content but in that case the xsi:nil attribute needs 
to be set to true. I have not used it in a real application but I 
believe it is useful when you want to express data structures in XML and 
you need the option to be able to not specify any value for the fields, 
similar with setting a variable to null in a programming language like Java.

If you want an element to have some content then how you specify that 
depends whether its content is
* element only
* specified by a simple type
* mixed (elements and text)

In the first case when an element contains only other elements than you 
need to make sure that not all the child elements are optional so you 
have some required content.

In the second case it depends on the type set on an element. If the type 
does not accept the empty string as a valid value then you do not need 
to specify anything else. If the empty string is allowed than you can 
try specifying a constraining facet on that type, for instance in case 
of xs:string you can specify that the minimum length should be greater 
than zero.

In the third case it is a little more difficult because XML Schema does 
not enforce constraints on the text part of an element that contains 
mixed content (both elements and text). The most you can do probably is 
to deal with that as in case of element only content and require some 
structure inside that element.

Of course if you allow for instance Schematron embedded rules in your 
schema then this constraint can be easily expressed as a Schematron rule.

Best Regards,
George
---------------------------------------------------------------------
George Cristian Bina
<oXygen/> XML Editor, Schema Editor and XSLT Editor/Debugger
http://www.oxygenxml.com

Timothy Reaves wrote:
> On Thu, July 26, 2007 10:51, Timothy Reaves wrote:
>> I'd like to have my schema specify that not only are certain elements
>> required, but that they can't be blank.  I can't seem to find how to
>> specify this.  I thought it was the nillable attribute, but that doesn't
>> prevent blank elements.
>>
> 
> Got this one figured out.  Nevermind. :-}
> 
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