TAP RFC [MTIME]

[Douglas Tody]

Hi -

An additional point to note about MTIME is that originally this was
part of ParamQuery.  It was orphaned when the ParamQuery service
operation was removed in a later version of the document.  It has
never been clear how MTIME would work with ADQL since one would have
to use an ADQL query to specify the table to be queried with MTIME,
which doesn't make much sense.  If we move MTIME back to the param
query (PQL now), then things are much better as the query is by
definition limited to a single table and FROM can be used to specify
the table name, plus we have consistency with the use of MTIME in
other parameter-based DAL interfaces.  Hence a reasonable approach
here is to move this to PQL and prototype it there as an advanced
capability along with GDS and the like.

 	- Doug