OK, I took a look and a quick workaround is to separate the xml and json types into separate methods like this (I removed the parameters for clarity):
<application xmlns:xsd="
http://www.w3.org/2001/XMLSchema" xmlns="
http://research.sun.com/wadl/2006/10">
<resources base="
http://example.com/">
<resource path="norm">
<method id="normalization-and-extraction-xml" name="POST">
<doc>
Post single list for normalization and/or extraction. HTTP respose contains the results.
</doc>
<request>
<representation id="AttachmentXml" mediaType="application/xml" status="200" element="nm:ExtractAndNormalize">
<doc>
ExtractAndNormalize.xsd
</doc>
</representation>
</request>
<response>
<representation id="AcceptXml" mediaType="application/xml" element="nm:ExtractAndNormalize" status="200"/>
</response>
</method>
<method id="normalization-and-extraction-json" name="POST">
<doc>
Post single list for normalization and/or extraction. HTTP respose contains the results.
</doc>
<request>
<representation id="AttachmentJson" mediaType="application/json" status="200">
<doc>
JSON equivalent of ExtractAndNormalize.xsd
</doc>
</representation>
</request>
<response>
<representation id="AcceptJson" mediaType="application/json" status="200"/>
</response>
</method>
</resource>
</resources>
</application>
I realize this isn't ideal since a client might want to send xml and get back json (or vice versa) so I'll continue to look at this but I thought an early solution might be useful in case you are blocked by it.
Marc.