[TAP] Parameter query (PQL) V0.2 draft

[Douglas Tody]

V0.2 of the TAP parameterized query (PQL) has been posted to the TWiki.
This can be found at

     http://www.ivoa.net/cgi-bin/twiki/bin/view/IVOA/TableAccess

The most notable changes were to make PQL more explicitly oriented
towards table queries, and addition of an "advanced topics" section
where multi-position (multicone) queries, metadata queries, etc. are
explicitly specified (merely specifying the individual parameters
is not enough as these more advanced capablities define additional
semantics).

Also, a new section on the Generic Dataset query has been added.
This is in the spirit of PQL as a general parameter-based query for
any type of data (if not a true language), using the Generic Dataset
(Observation) data model as the basis for the query mechanism.
The BAND and TIME parameters have been moved into the proposed
TAP-based GDS query which will provide a well-defined data model for
these and other GDS-related parameters.  (The GDS model is described in
the DAL2 architecture doc which is also available on the page above).

 	- Doug