Question

We have a generated XML schema that I am a bit confused on the meaning of the schema (ie, what exactly it is looking for to be valid)

<xs:element name="element">
  <xs:complexType>
    <xs:sequence>
      <xs:element minOccurs="0" name="firstitem_id" type="xs:integer" />
      <xs:element minOccurs="0" maxOccurs="unbounded" name="seconditem_id">
        <xs:complexType>
          <xs:simpleContent>
            <xs:extension base="xs:integer">
              <xs:attribute name="order" type="xs:integer" />
            </xs:extension>
          </xs:simpleContent>
        </xs:complexType>
      </xs:element>
    </xs:sequence>
    <xs:attribute name="id" type="xs:integer" use="required" />
  </xs:complexType>
</xs:element>

From what I was told, this is really asking for the following:

<element>
  <firstitem_id>17</firstitem_id>
  <seconditem_id order="2">34</seconditem_id>
</element>

Is this true, and why would this specification show up in this manner?

Answer 1

That schema fragment defines the following structural rules for the “element” element:

• It’s name is “element”
• It must have an “id” attribute with an integer value (your example does not)
• The child element “firstitem_id”
  • is optional
  • can only be used once
  • it’s value must be an integer
  • and it must appear before “seconditem_id” if both elements are in the instance doc
• The child element “seconditem_id”
  • is also optional
  • can appear more than once
  • it’s value must be an integer

This is one valid example:

<element id="1">
  <firstitem_id>17</firstitem_id>
  <seconditem_id order="2">34</seconditem_id>
</element>

This is another:

<element id="2">
  <seconditem_id order="2">34</seconditem_id>
</element>

This is another:

<element id="3">
  <firstitem_id>17</firstitem_id>
</element>

And another:

<element id="4">
  <firstitem_id>17</firstitem_id>
  <seconditem_id order="2">34</seconditem_id>
  <seconditem_id order="3">35</seconditem_id>
</element>

And another:

<element id="5">
  <seconditem_id order="2">34</seconditem_id>
  <seconditem_id order="3">35</seconditem_id>
</element>