outputFormat

                     The outputFormat attribute is used to specify what schema
                     description language should be used to describe features.
                     The default value of 'text/xml; subtype=3.1.1' means that
                     the WFS must generate a GML3 application schema that can
                     be used to validate the GML3 output of a GetFeature
                     request or feature instances specified in Transaction
                     operations.
                     For the purposes of experimentation, vendor extension,
                     or even extensions that serve a specific community of
                     interest, other acceptable output format values may be
                     advertised by a WFS service in the capabilities document.
                     The meaning of such values in not defined in the WFS 
                     specification.  The only proviso is such cases is that
                     clients may safely ignore outputFormat values that do
                     not recognize.