TAP VOSI Information

[Patrick Dowler]

On Tuesday 24 November 2009 05:20:07 Tom McGlynn wrote:
> The current TAP specification is a bit unclear about this.  The current 
> draft doesn't mention VARBINARY data at all. 

The TAP spec very explicitly mentioned VARBINARY and BLOB and how they are to 
be described.

A column of type VARBINARY is mapped as Mark said:

<FIELD datatype="unsignedByte" arraysize="*"  .... />

and it would be correct to include xtype="adql:VARBINARY" as well. The service 
could put something more specific for arraysize. Since the datatype and 
arraysize are sufficient, the xtype is redundant in this case and could in 
principle be used for something else; we debated this extensively and I did 
bring up the idea of embedding a small image in the results but that idea 
never got any traction...

The only fields where xtype is required to be an adql-specific value are
TIMESTAMP, POINT, REGION. For those, datatype="char" and arraysize="*" but 
they are not simply strings. What needs to be clear in the spec is that these 
are the only cases where xtype is mandated. In other cases, both uploads and 
results are sensible using the other field attributes.

So, right now the TAP spec does not specify how to deal with an embedded 
binary image; I think we should leave that to 1.x but I also think people 
could experiment with using xtype without being non-compliant with the TAP 1.0 
spec.

-- 

Patrick Dowler
Tel/Tél: (250) 363-0044
Canadian Astronomy Data Centre
National Research Council Canada
5071 West Saanich Road
Victoria, BC V9E 2M7

Centre canadien de donnees astronomiques
Conseil national de recherches Canada
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Victoria (C.-B.) V9E 2M7