pattern matching in SLAP 2 protocol

[nicolas]

Dear DAL and Apps members,

In the current draft of the Simple Line Access Protocol version 2 
(SLAP2), we have introduced a SPECIES parameter where the user
can specify a species name (i.e CH4, CO2 ... ). In order to add 
flexibility, this parameter can accept
pattern matching expressions.

In the current specification, we use SQL-like patterns as users are already
familiar with them through SQL and ADQL (%, _).
Another possibility would be to use shell patterns instead (?, *).

To illustrate the difference, searching for a species whose name starts 
with the letter C:

   SQL pattern  : SPECIES=C%
   Shell pattern: SPECIES=C*

And searching for a 3-character species name starting with C:

   SQL pattern  : SPECIES=C__
   Shell pattern: SPECIES=C??

 From an implementor point of view, SQL patterns have the advantage that 
they can be used
directly as-is if there is an SQL database behind the service. On the 
other hand, shell patterns
are widely used outside of the database world.

While discussing this with Markus, it appeared to be the first time 
RE-like expressions are used in an
IVOA protocol. This choice could set a precedent. We would therefore like
to get your opinion: should we stick with SQL patterns or use shell 
patterns?


Best regards

-- 
Nicolas Moreau
LUX - Paris Observatory

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