This note describes the syntax for the various expressions for
selecting data from the Measurement Set. This is the syntax that is
implemented in the
MSSelection module of CASA. The syntax is
derived from an
earlier
note
on syntax definition. All expressions consist of a comma or
semi-colon separated list of specifications. Except channel
selection, the final product of parsing the expressions is a Table
Expression Node (TEN) which can be used to construct a selected
Measurement Set. Higher level global methods to return a selected MS,
given the user supplied expressions, are also provided as part of the
MSSelection module.
Error handling is done via the C++ exception handling mechanism. The
exceptions thrown by the MSSelection module are of type MSSelectionError which is derived from AipsError class. The
exceptions generated from each individual expression parser are
further specializations of the MSSeletionError class.
Application layer code therefore can have a finer level control on
error handling.
