XML Schema Question

Question

Is it possible to define an XML Schema (XSD) to correctly describe a document such as the following?

<root>
    <str name="status">success</str>
    <str name="message">Your request has been processed successfuly.</str>
</root>

The problem might be that the <str> tags have an attribute (name) as well as string values. I would be grateful if anyone could come up with an XML Schema for this piece of XML, since I am kind of stuck at this point. My best attempt so far is shown below, but botice that the <str> element cannot have a type (such as xsd:string) in this context.

  <xs:element name="object">
  <xs:complexType>
    <xs:sequence>
      <xs:element name="str" minOccurs="2" maxOccurs="2">
        <xs:complexType>
          <xs:sequence>
            <xs:element name="productName" type="xs:string"/>
          </xs:sequence>
          <xs:attribute name="name" type="xs:string" use="required"/>
        </xs:complexType>
      </xs:element>
    </xs:sequence>
  </xs:complexType>
  </xs:element>

score 1 · Accepted Answer · answered May 03 '11 at 17:02

Your constraints are not entirely clear, so a number of schemas would validate the XML depending on how loose/tight you would want the validation to be. This example shows a schema that mandates exactly two elements inside the element and they must have a "name" attribute with the values "status" or "message".

<?xml version="1.0" encoding="utf-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="root">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="str" type="StrType" minOccurs="2" maxOccurs="2"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:complexType name="StrType">
    <xs:simpleContent>
      <xs:extension base="xs:string">
        <xs:attribute name="name" type="StrAttribute" use="required" />
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>

  <xs:simpleType name="StrAttribute">
    <xs:restriction base="xs:string">
      <xs:enumeration value="status"/>
      <xs:enumeration value="message"/>
    </xs:restriction>
  </xs:simpleType>
</xs:schema>

Of course, this would allow two elements both with the name attribute set to "message", or with "message" first, then status. I believe the schema cannot define a sequence containing two elements of the same name but different types which you would need if you required the validation to ensure that the first always contained "status" and the second one contained "message".

Thanks a lot. This really pointed me in the right direction. The order of the str elements is not really important. However, I would like to make sure that exactly one of them has the "status" attribute and exactly one of them has the "message" attribute. Do you think this would be possible? — Epicurus, May 06 '11 at 07:07
I am not 100% but I think it is not possible. XSD cannot define the elements with the same name in the same sequence to be of different types. If you can change the XML you should perhaps have different element names, and instead of . Related questions: http://stackoverflow.com/questions/1306305/xsd-same-element-different-types http://stackoverflow.com/questions/827051/xml-schema-for-sequence-of-elements-with-same-name-but-different-attribute-values — fredw, May 10 '11 at 17:25

XML Schema Question

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