New UCD1+ for SIA protocol
arots at head.cfa.harvard.edu
Wed Mar 24 11:46:14 PST 2004
I had asked that SCORE (used to be GRADE) be included in the list of
optional input and output parameters and there seemed to be agreement
that it is a useful thing.
SCORE is a floating point value that ranks returned images according
to their relevance for the query as perceived by the server. This is
meant to aid the client (especially the non-specialist client) in
choosing from a list of images in case more than one image satisfies
the query criteria. The scale is always relative and only
meaningful in the context of the result in which it is provided. It
may measure things like exposure time, image quality, proximity to the
specified position, resolution, etc.
SCORE is a string and may assume two values:
If multiple images satisfy the query criteria, only the one with the
highest value of SCORE (in output) is returned.
(default) All images satisfying the query criteria are returned.
This issue is important for archives of pointed observations where
dozens of images may be available satisfying a single query. Expert
users may want to see the metadata on all of them and choose, but
less sophisticated users and more general services (the issue came up
in some of our prototypes/demos as a real problem!) are more likely
get annoyed and say: just get me what you think is the best one. And
that's what this is about.
There is no UCD that fits this, it's a context-dependent thing and,
besides, it has a different datatype on input and output.
But I'd appreciate its being added.
Roy Williams wrote:
> Dear UCD and DAL folks
> Three of us (Sebastian Derriere, Andrea Preite-Martinez, myself) have been
> working on an update for the SIA protocol that uses the standard UCD set,
> now called UCD1+, rather than the ad hoc namespace VOX that SIA 1.0 has been
> In the following, all UCD from the original SIA specification are listed
> below. The old SIA UCD is written first, then the suggested new UCD1+ is
> written in the line beginning "-->"
> The UCD1+ is not fully documented yet, but you can find a dictionary from
> UCD1 to UCD1+ at
> The SIA protocol is defined at
> The new SIA will be version 1.1, and we are hoping to draft and approve this
> at the IVOA meeting at the end of May.
> Thank you for your comments and suggestions on these new assignments
> Andrea, Roy, Sebastian
> --> meta.title
> containing a short (usually one line) description of the image. This should
> concisely describe the image to a user, typically identifying the image
> source (e.g., survey name), object name or field coordinates,
> bandpass/filter, and so forth.
> --> meta.id;instr
> identifying the instrument or instruments used to make the observation,
> --> time.epoch
> representing the mean modified Julian date of the observation.
> --> pos.eq.ra
> representing the ICRS right-ascension of the center of the image.
> --> pos.eq.dec
> representing the ICRS declination of the center of the image.
> --> pos.wcs.naxes
> specifying the number of image axes.
> --> pos.wcs.naxis
> with the array value giving the length in pixels of each image axis.
> --> instr.scale
> with the array value giving the scale in degrees per pixel of each image
> --> meta.code.mime
> specifying the MIME-type of the object associated with the image acref,
> --> pos.frame
> representing the coordinate system reference frame, selected from "ICRS",
> "FK5", "FK4", "ECL", "GAL", and "SGAL".
> --> time.equinox
> representing the Equinox (not required for ICRS) of the coordinate system
> --> pos.wcs.ctype
> the array value being the three-character code ("TAN", "ARC", "SIN", and so
> forth) specifying the celestial projection
> --> pos.wcs.crpix
> with the array value specifying the image pixel coordinates of the WCS
> reference pixel. This is identical to "CRPIX" in FITS WCS.
> --> pos.wcs.crval
> with the array value specifying the world coordinates of the WCS reference
> pixel. This is identical to "CRVAL" in FITS WCS.
> --> pos.wcs.cdmatrix
> with the array (matrix) value specifying the WCS CD matrix. This is
> identical to the "CD" term in FITS WCS, and defines the scale and rotation
> (among other things) of the image.
> --> instr.bandpass
> identifying the bandpass by name (e.g., "V", "SDSS_U", "K", "K-Band", etc.).
> --> meta.unit
> identifying the units used to represent spectral values, selected from
> "meters", "hertz", and "keV".
> --> em.wl OR em.freq OR em.energy
> specifying the characteristic (reference) frequency, wavelength, or energy
> for the bandpass model.
> --> em.wl;stat.max OR em.freq;stat.max OR em.energy;stat.max
> specifying the upper limit of the bandpass.
> --> em.wl;stat.min OR em.freq;stat.min OR em.energy;stat.min
> specifying the lower limit of the bandpass.
> --> meta.code
> specifying the type of processing done by the image service to produce an
> output image pixel.
> --> meta.ref.url
> specifying the URL to be used to access or retrieve the image.
> --> time.interval;stat.min
> specifying the minimum time to live in seconds of the access reference.
> --> phys.size;meta.file
> representing the actual or estimated size of the encoded image in bytes (not
Arnold H. Rots Chandra X-ray Science Center
Smithsonian Astrophysical Observatory tel: +1 617 496 7701
60 Garden Street, MS 67 fax: +1 617 495 7356
Cambridge, MA 02138 arots at head.cfa.harvard.edu
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