- uws.service.UWS.VERSION  (static final)
  - tap.resource.TAP.VERSION (static final)

Dealing with several protocol versions in the same time is quite difficult and
may significantly alter the libraries API in an unstable way. That's why, for
the TAP and UWS libraries, only one version is implemented (i.e. the last one).
To use a older version of the protocol, one must use an older version of the
corresponding library.

About the versioning of the ADQL standard, there is no need to set any version
number somewhere because a different ADQL version implies a different grammar.
It means that a different parser is required for each ADQL version. For the
moment, there is only one version, so no need to change anything to the ADQL
library about ADQL version. Later, ADQLParser should become an interface and
a factory will have to be used in order to get the parser corresponding to the
desired ADQL version.