TAP/VOSI 1.1: required type system?

[Marco Molinaro]

Hi Markus, all,
if a type system (and inheritance) is in place, I'm not sure that it is a
good idea
to mandate a single type system for a protocol.
I can agree on the not neat extension mechanism for data types we have in
place.
Wouldn't it be preferable to have the type system cleaned up, rather than
hacking
the behaviour at protocol level?

In any case I wouldn't touch VOSI, it has (could have) a more general use
than for TAP only.

Beware, this is a quick reply, I didn't investigate what drawbacks can
bring up
re-fitting the type systems out there.

Cheers,
     Marco

2015-12-16 12:38 GMT+01:00 Markus Demleitner <msdemlei at ari.uni-heidelberg.de
>:

> Hi,
>
> While playing with a table that actually has a region-valued column
> (in case you're curious: antares10.data on ivo://org.gavo.dc/tap), I
> was horrified to see it is shown in TOPCAT's metadata browser as
> being of type char[*].
>
> The reason for that is that that's what I'm saying on the VOSI
> endpoint:
>
>   <column>
>     <name>origin_est</name>
>     <description>A circle around the most likely position
>     with ang_error radius (for convenient matching)</description>
>     <ucd>obs.field</ucd>
>     <dataType arraysize="*" xsi:type="vs:VOTableType">char</dataType>
>     <flag>nullable</flag>
>   </column>
>
> Background: VODataService 1.1 defines several type systems --
> essentially, the inheritance tree looks like this:
>
>   DataType
>     |
>     +--- SimpleDataType (integer, real, complex, boolean, char, string)
>     |
>     |
>     +--- TableDataType
>               |
>               +--- TAPType
>               |
>               +--- VOTableType
>
> and VOTableType doesn't really contain the VOTable's xtype (we could
> probably hack it through extendedSchema and extendedType, but I'd
> rather wait how bad the xtype thing will really turn out).
>
> When writing DaCHS' VOSI interface, I figured that since I'm usually
> producing VOTables, writing my types as VOTableTypes would be the
> most sensible thing to do.
>
> Turns out it's not.
>
> Leaving aside my general skepticism towards stealthily expanding
> VOTable's type system with xtype, which I believe will keep causing
> lots of headache: I believe to keep clients and users sane, we should
> in TAP 1.1 (and perhaps VOSI 1.1) say that in the table metadata of
> TAP endpoints, services really-really-should use the vs:TAPType type
> system (which probably needs to be fixed soon to include CIRCLE and
> POLYGON), and announce that in the next major version, that will
> become a must.
>
> Thoughts?
>
> Cheers,
>
>             Markus
>
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