Capability to produce XML output was added to the wwwblast package. XML definition of BLAST output is tied to the simple ASN.1 specification designed for this case. These definitions may be found online at: http://www.ncbi.nlm.nih.gov/data_specs/.
XML may be printed by setting 'Alignment view' to 'BLAST XML' before the submission of the search. Users will need to open the page source using 'View Page source' menu from the browser to see the complete XML document. Result for multiple queries will be a file with multiple XML records concatenated together. In another word, wwwblast version 2.2.15 still generates the XML output in the old format.
We do not recommend running large scale searches to get the XML output using this wwwblast package. Users, who need the xml output, should take a look at command line standalone BLAST package instead.