outputFormat

                     The outputFormat attribute is used to specify the output
                     format that the Web Feature Service should generate in
                     response to a GetFeature or GetFeatureWithLock element.
                     The default value of 'text/xml; subtype=gml/3.1.1'
                     indicates that the output is an XML document that
                     conforms to the Geography Markup Language (GML)
                     Implementation Specification V3.1.1.
                     For the purposes of experimentation, vendor extension,
                     or even extensions that serve a specific community of
                     interest, other acceptable output format values may be
                     used to specify other formats as long as those values
                     are advertised in the capabilities document.
                     For example, the value WKB may be used to indicate that a 
                     Well Known Binary format be used to encode the output.