[PQL] scope

[Patrick Dowler]

I would like to re-start the discussion of the scope of PQL. Please post ideas 
and comments.

Pat

On 2009-02-24 10:21:12 Patrick Dowler wrote:
> Now that the way forward is clear, we need to define the scope of the PQL
> document and decide if we should rename it.
>
> At a minimum, P?? is a set of parameters that are are defined consistently
> and then used by multiple DAL services. The goal is simply that there is
> only one meaning for a specific parameter name and there is a definitive
> document that specifies it. It is clear that specific service
> specifications must extend this with either additional parameters (as in
> SSA) or by defining
> standard "property names" to be used with WHERE.
>
> At the other end, one could formalise PQL into a query language along the
> lines of query-by-example or some sort of template-matching scheme. This
> would be a smaller scope but a (more) complete query language.
>
> As it stands right now:
>
> * P?? includes the specification of the syntax for range (/) and list (,)
> values, qualifiers (;) and symbolic values (@ and/or $).
>
> * P?? includes the standard query parameters (POS, SIZE, BAND, TIME,
> REGION).
>
> * P?? includes FROM for use by services with multiple things to query
> (currently only TAP, but could be others since "multiple things to query"
> is dependent on what the data model looks like). It also includes WHERE for
> cases where services expose "names" of things via metadata (columns in TAP)
> or where they standardise these "names" (utypes maybe) in the spec or a
> related document (a data model). I think these could have use beyond TAP.
>
> Questions:
>
> Should P?? include non-query parameters? Specifically, I am thinking about
> MAXREC, MTIME, FORMAT. These are used in multiple specs.
>
> Should P?? include standardised way to upload things, without saying what
> they are? That is, standardise the UPLOAD=name,URI parameter? Standardise
> the inline upload (and where the name comes from in there)?
>
> Basically, is P?? limited to the what is needed to pose a query or is it
> generally "all the standard DAL parameters"?



-- 

Patrick Dowler
Tel/Tél: (250) 363-0044
Canadian Astronomy Data Centre
National Research Council Canada
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