Xml – using xml type attribute for derived complex types

schemaxml

I'm trying to get derived complex types from a base type in an xsd schema.

it works well when I do this (inspired by this):

xml file:

     <person
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:type="Employee">
        <name>John</name>
        <height>59</height>
        <jobDescription>manager</jobDescription>
     </person>

xsd file:

     <xs:element name="person" type="Person"/>

         <xs:complexType name="Person" abstract="true">
         <xs:sequence>
            <xs:element name= "name" type="xs:string"/>
            <xs:element name= "height" type="xs:double" />
         </xs:sequence>
         </xs:complexType>

         <xs:complexType name="Employee">
         <xs:complexContent>
             <xs:extension base="Person">
                <xs:sequence>
                   <xs:element name="jobDescription" type="xs:string" />
                </xs:sequence>
              </xs:extension>
          </xs:complexContent>
         </xs:complexType>

However, if I want to have the person element inside, for example, a sequence of another complex type, it doesn't work anymore:

xml:

    <staffRecord>
      <company>mycompany</company>
      <dpt>sales</dpt>
      <person
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:type="Employee">
        <name>John</name>
        <height>59</height>
        <jobDescription>manager</jobDescription>
      </person>
    </staffRecord>

xsd file:

<xs:element name="staffRecord">
    <xs:complexType>
    <xs:sequence>
        <xs:element name="company" type="xs:string"/>
        <xs:element name="dpt" type="xs:string"/>

        <xs:element name="person" type="Person"/>

            <xs:complexType name="Person" abstract="true">
             <xs:sequence>
                <xs:element name= "name" type="xs:string"/>
                <xs:element name= "height" type="xs:double" />
             </xs:sequence>
            </xs:complexType>

            <xs:complexType name="Employee">
             <xs:complexContent>
                <xs:extension base="Person">
                   <xs:sequence>
                      <xs:element name="jobDescription" type="xs:string" />
                   </xs:sequence>
                 </xs:extension>
             </xs:complexContent>
            </xs:complexType>


    </xs:sequence>
    </xs:complexType>
</xs:element>

When validating the xml with that schema with xmllint (under linux), I get this error message then:

config.xsd:12: element complexType:
Schemas parser error : Element
'{http://www.w3.org/2001/XMLSchema}sequence':
The content is not valid. Expected is
(annotation?, (element | group |
choice | sequence | any)*). WXS schema
config.xsd failed to compile

Any idea what is wrong ?

David

Best Answer

The root element of your XML file should have all complex types defined in the namespace.

http://www.datypic.com/books/defxmlschema/chapter13.html

Related Solutions

R – XML Schema – Key in sequence

The key element is not supposed to go inside the sequence element. Instead, you put it as a child of the xs:element that defines ReferralCollection. The selector and field are child elements of the key element that define what is supposed to be unique. Both are XPath expressions. The selector value sets up the XPath context, and the field elements (there can be more than one) define the combination of values that are supposed to be unique. So in your case, the key element might look something like this:

<xs:key name="URL">
  <xs:selector xpath="."/>
  <xs:field xpath="rd:keyword"/>
</xs:key>

The selector here selects the element itself, that is, ReferralCollection. Then, in that context, the field element denotes the values of the keyword elements, which are thus constrained to be unique. The value of an element in XPath is its text content.

I haven't done much with key elements (or XML Schema in general), so some details above might not be correct, but the basic idea is what I explained, so it should be easy to fix any mistakes I made. Oh, also note that I used the rd prefix for your READOO namespace; in my experience using explicit prefixes is always best when dealing with XPath, so you need the appropriate xmlns:rd attribute in your schema to make this work.

EDIT: So it seems you want something like this:

<xs:element name="ReferralCollection">
  <xs:complexType>
    <xs:sequence>
      <xs:element name="URL" maxOccurs="unbounded">
        <xs:complexType>
          <xs:sequence>
            <xs:element name="stem" type="xsd:string"/>
            <xs:element name="keyword" maxOccurs="unbounded">
            ...
            </xs:element>
          ...
  </xs:complexType>

  <xs:key name="URL">
    <xs:selector xpath="./URL"/>
    <xs:field xpath="stem"/>
  </xs:key>
</xs:element>

Is this closer to what you meant? It has URL elements, one or more, each containing a stem element followed by one or more keyword elements. The key constraint should make the contents of the stem elements unique.

Python – How to parse XML and count instances of a particular node attribute

I suggest ElementTree. There are other compatible implementations of the same API, such as lxml, and cElementTree in the Python standard library itself; but, in this context, what they chiefly add is even more speed -- the ease of programming part depends on the API, which ElementTree defines.

First build an Element instance root from the XML, e.g. with the XML function, or by parsing a file with something like:

import xml.etree.ElementTree as ET
root = ET.parse('thefile.xml').getroot()

Or any of the many other ways shown at ElementTree. Then do something like:

for type_tag in root.findall('bar/type'):
    value = type_tag.get('foobar')
    print(value)

And similar, usually pretty simple, code patterns.

Best Answer

Related Solutions

R – XML Schema – Key in sequence

Python – How to parse XML and count instances of a particular node attribute

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