Question

Here is a schema file, midi.xsd that defines a type, note, used to store MIDI note values:

<?xml version="1.0" encoding="utf-8"?>

<xs:schema elementFormDefault="qualified"
           xmlns:xs="http://www.w3.org/2001/XMLSchema">

  <xs:simpleType name="note">
    <xs:restriction base="xs:integer">
      <xs:minInclusive value="0"/>
      <xs:maxInclusive value="127"/>
    </xs:restriction>
  </xs:simpleType>

</xs:schema>

Here is another schema file, octaves.xsd which uses midi.xsd to help define the layout to be enforced on an XML file containing data about octaves:

<?xml version="1.0" encoding="utf-8"?>

<xs:schema elementFormDefault="qualified"
           xmlns:xs="http://www.w3.org/2001/XMLSchema">

  <xs:include schemaLocation="midi.xsd"/>

  <xs:element name="octaves">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="octave">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="name" type="xs:string" />

              <xs:element name="midi">
                <xs:complexType>
                  <xs:sequence>

                    <xs:element name="value" type="xs:integer" />
                    <xs:element name="from" type="note" />
                    <xs:element name="to" type="note" />

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

            </xs:sequence>

            <xs:attribute name="index" type="xs:integer" />

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

</xs:schema>

This is fine, and works exactly as you would expect it to, except that I have another requirement: I want note to be in its own namespace, midi, so that

<xs:element name="from" type="note" />

becomes

<xs:element name="from" type="midi:note" />

Try as I might, I cannot get this to work. My attempts have included use of the targetNamespace attribute in various places, the import element, and liberal use of xmlns:midi="...", but to no avail. I’d post one of these attempts here, were it not so cringe-worthy.

Could some kind soul point me in the right direction? I’m pretty sure the problem is to do with the fact that midi.xsd is a local file; it has never been, and never will be, hosted on a web server.

Answer 1

Change midi.xsd to be:

<xs:schema elementFormDefault="qualified"
       xmlns:xs="http://www.w3.org/2001/XMLSchema"
       targetnamespace="/my/midi/namespace">

And then change octaves.xsd to say:

<xs:schema elementFormDefault="qualified"
       xmlns:xs="http://www.w3.org/2001/XMLSchema"
       xmlns:midi="/my/midi/namespace">

   <xs:import namespace="/my/midi/namespace" schemaLocation="midi.xsd"/>

   ...

   <xs:element name="from" type="midi:note" />

Note the use of xs:import rather than <xs:include> The two are very different – you use import for bringing in other namespaces, and include for inline inclusion of other schema files into the current namespace.

Note also that /my/midi/namespace can be anything you want, it’s an arbitrary identifier.

I’m pretty sure the problem is to do with the fact that midi.xsd is a local file

Nope, not relevant.