XLink conformant elements must contain a type attribute. This is it's definition.
token
      <simpleType name="basicLinkType" final="#all" >
  <restriction base="token">
    <enumeration value="simple" />
    <enumeration value="extended" />
    <enumeration value="locator" />
    <enumeration value="arc" />
    <enumeration value="resource" />
    <enumeration value="title" />
    <enumeration value="none" />
  </restriction>
</simpleType>