Spectrum data model
m.b.taylor at bristol.ac.uk
Wed Sep 13 08:46:57 PDT 2006
On Wed, 13 Sep 2006, Matthew Graham wrote:
> Mark Taylor wrote:
> > On Wed, 13 Sep 2006, Matthew Graham wrote:
> >> Hi,
> >>> Otherwise, it seems to me that what is called for is an additional
> >>> field in the SSAP response which names the specific serialization
> >>> format, if known. This would require assigning some sort of name
> >>> to the XML, FITS and VOTable formats defined in the Spectral DM
> >>> document (presumably a URI of some sort).
> >>> Mark
> >> The VOSpace specification uses uris to identify data formats and the
> >> idea is that these will be registered somewhere, e.g.
> >> ivo://net.ivoa.vospace/views/fits-table. It would make sense for both
> >> groups at least to use the same uris.
> > Matthew
> > Dave Morris made this point to me at the VOTech meeting in Strasbourg
> > last week, but I'm not sure I was thinking very clearly about it at
> > the time. A question which occurs to me now: does VOSpace require
> > a single data format per file (or entry, or whatever the correct
> > term is), or can a single file be labelled with multiple different
> > data format URIs at the same time?
> > Mark
> If the data object is stored in a StructuredDataNode then multiple data
> views are allowed: this is, of course, implementation dependent but the
> idea is that if a VOSpace supported this, a FITS image might be
> retrievable as a JPEG or a GIF, etc. or a FITS table as a VOTABLE or CSV.
> If the data object is stored in an UnstructuredDataNode then essentially
> bits in = bits out so only one view is allowed and that is the input view.
I wasn't thinking about data views (in the VOSpace sense) here.
What I had in mind was the fact that assigning a single registered
URI to describe the data type of a file in VOSpace may be problematic
if the resolution of these types is sufficient to do things like
distinguish different FITS-based spectrum serializations.
The kind of data format identifier one would need to label a specific
spectrum serialization, which is what I was suggesting in my original
message, would have to be something with at least a level of detail like
"VOTable serialization of spectrum as defined by the Spectral DM standard",
and possibly be labelled by a version of that document as well.
This may be too specific for the kind of data type you'd want to
attach to a file in VOSpace, which I'd have thought would be nearer
to MIME types, e.g. "this is a VOTable". Of course, it all depends
on the requirements of the client that is retrieving that file,
which makes it problematic to provide a single one-size-fits-all
Mark Taylor Astronomical Programmer Physics, Bristol University, UK
m.b.taylor at bris.ac.uk +44-117-928-8776 http://www.star.bris.ac.uk/~mbt/
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