DM work package : Utypes definition and syntax

Work is currently taking place in UtypesTigerTeam.

Last iterations on the definitions (presentations @ interop meetings)

• at Interop May 2010 in Victoria UtypesIntheIVOA.pdf
• at Interop May 2011 in Napoli UtypesIntheIVOA-2011.pdf
• Utypes session at Interop Oct 2011 in Pune http://wiki.ivoa.net/twiki/bin/view/IVOA/InterOpOct2011DM

What are Utypes for

Utypes are names that we can attach to a piece of metadata in order to point to the same concept expressed in a VO data model.
Ex: astrometry statistical error = 0.02 arcsec

This metadata can be represented in the VO using the Characterisation data model by : char:Spatial.Accuracy.StatError.Refval

If we associate "astrometry statistical error" with this utype, we can derive various properties like:

1. the concept of astrometrical error is the same as the one described in the model.
2. This concept relies on accuracy along the spatial axis.
3. If we provide a value with this utype, it is stored in the same type as the data model element and if mentionned in the restricted units defined by the model.

How can I find which Utype is relevant for my data collection

1. Select an IVOA data model to which you want to be compliant. Ex : Characterisation Data Model
2. Browse the Utype list and its documentation to select the appropriate Utype list for your metadata description
3. Check wether all mandatory Utypes are filled in .

Examples

- For a Fits image : FITS keyword RESOL will map SpatialAxis.Resolution.RefVal in the Characterisation Data Model utypes list

- For a Fits simple spectrum : FITS keyword SPECTRES will map SpectralAxis.Resolution.RefVal

If you publish your data with CharacterisationDM-v1.11 , you can use the CAMEA VO Tool (http://eurovotech.org/twiki/bin/view/VOTech/CharacEditorTool) to check the Utype assignation, and verify if your description is compliant to this model.

• WD-Utypes-0.3-20090522.pdf: Utype preliminary WD