xxtest.xsd

<?xml version="1.0" ?>
<xsd:schema              xmlns:xsd       = 'http://www.w3.org/2001/XMLSchema'>

  <xsd:element           name            = 'xxtest'
                         type            = 'xxtest'/>
  <xsd:complexType       name            = 'xxtest'>
    <xsd:sequence>
      <xsd:element       name            = 'a'
                         type            = 'DataString'
                         maxOccurs       = 'unbounded'/>
    </xsd:sequence>
  </xsd:complexType>

  <xsd:simpleType        name            = 'DataString'>
    <xsd:restriction     base            = 'xsd:string'>
    <!--
    Original test was <minLength value="1"/>, but that was replaced
    by a regular expression which ensures that the text content has
    no leading or trailing whitespace, and has no sequences of more
    than one space character, and no other whitespace characters.
    -->
      <xsd:pattern       value           = '[^\s]+( [^\s]+)*'/>
    </xsd:restriction>
  </xsd:simpleType>

</xsd:schema>