A validator for IVOA identifiers, checking
conformity to version 2 of the specification.
The service returns results in a tabular format, where an identifier is
valid if no row with msg_type="ERROR" is present.
As per DALI, the format of the table returned can be controlled
through the RESPONSEFORMAT parameter; for machine consumption, the
most useful values for that parameter are probably json and votable.
The code used here is available at
http://svn.ari.uni-heidelberg.de/svn/gavo/hdinputs/ivoidval