RE: extension element question

Element with subelements and/or attributes are complex types. Elements that do not contain nested elements but instead a single value have simple content. Every element has to have a type [even if it is xs:anyType]. To add attributes to a complex type with simple content means extending its underlying simple type. 
 

 -----Original Message----- 
 From: David.Cantrell@Gunter.AF.mil [mailto:David.Cantrell@Gunter.AF.mil] 
 Sent: Fri 10/25/2002 1:48 PM 
 To: xmlschema-dev@frink.w3.org 
 Cc: 
 Subject: extension element question
 
 


 Hello again schemers,
 
 I am going through the XFront schema tutorial[0] and have hit a spot that I
 don't quite understand.
 
 Why are the simpleContent and extension elements required here:
 
         <xsd:complexType name="linkType">
                 <xsd:simpleContent>
                         <xsd:extension base="xsd:string">
                                 <xsd:attribute name="title"
 type="xsd:string" use="required"/>
                                 <xsd:attribute name="action"
 type="xsd:string" use="required"/>
                         </xsd:extension>
                 </xsd:simpleContent>
         </xsd:complexType>
 
 I'm not extending any types, at least not intentionally, so I'm not sure why
 it's required. The element I'm trying to create should look like this:
 
         <link title="foo" action="bar"/>
 
 There are no child elements or character data, the element will always be
 empty except for the two required attributes.
 
 Also, I don't quite understand exactly what the simpleContent element really
 does. The MSXML docs state:
 
         "Contains extensions or restrictions on a complexType element with
 character data or a simpleType element as content and contains no elements."
 
 I don't fully understand exactly what that means. Since there is no CDATA
 and it is not a simpleType, and definitely does not contain any child
 elements, I see no reason for this element to be required.
 
 However, if I eliminate either the extension or the entire simpleContent
 wrapper, the validation fails and reports I did not declare a root element
 (not shown in the above schema snippet)... :(
 
 Thanks,
 -dave
 
 [0] http://www.xfront.com/#schema

Received on Friday, 25 October 2002 18:45:18 UTC