> Saxon doesn't, though it's been on my
> todo list for a long while.
> 
Now done, producing:

<definitions
xmlns:plnk="http://schemas.xmlsoap.org/ws/2003/05/partner-link/"
             xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
             xmlns:xalan="http://xml.apache.org/xslt"
 
xmlns:bpws="http://schemas.xmlsoap.org/ws/2003/03/business-process/"
             xmlns:xsd="http://www.w3.org/2001/XMLSchema"
             xmlns:tns="urn:bpel:jiap"
             xmlns="http://schemas.xmlsoap.org/wsdl/"
             targetNamespace="urn:bpel:jiap">
   <types><!--s/b: xmlns="http://www.w3.org/2001/XMLSchema"
-->
      <schema xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="urn:bpel:jiap&#xA;"/>
   </types>
</definitions>

(The algorithm is that if indenting is on, and the length of all
attributes/namespaces up to and including the current one exceeds 80, and
the attribute is not the first, then the attribute is output on a new line
aligned with the first attribute.)

Michael Kay
http://www.saxonica.com/