[Fwd: Re: First-attempt Catalogue DM for discussion]

[Ed Shaya]

-------- Original Message --------
Subject: 	Re: First-attempt Catalogue DM for discussion
Date: 	Fri, 17 Sep 2004 08:55:23 -0400
From: 	Ed Shaya <edward.j.shaya.1 at gsfc.nasa.gov>
To: 	Mark Taylor <m.b.taylor at bristol.ac.uk>
References: 
<Pine.LNX.4.44.0409171148160.10750-100000 at andromeda.star.bris.ac.uk>



>There are powerful aspects to a tree-like structure, but one important
>question is: how do you define what tree you're going to use?
>I'm not sure if you're suggesting that we decide on a particular
>tree that looks something like the above and hardwire that into the
>catalogue data model.  As you say it would make certain sorts of
>query very tidy, but people are always going to want some items
>which don't fit in well - for instance where do you put an
>observed object for which you have provenance, magnitudes and spectra,
>but as yet no classification?  The opposite approach is to have the tree
>in use defined on a per-catalogue basis, but this loses you a lot
>of the interoperability benefits.  Which did you have in mind?
>
>Mark
>
>  
>
Both!  If you don't know the classification yet,  they are astroObjects 
which is permitted at any level.  If they are real and you know from 
Lyman limit cutoff that they are beyond cz=8.3
<Universe>
   <region  type="redshiftCut">
      <redshift></unitless><value 
inequality="greaterThan">8.3</value></redshift>
      <astroObject name="A2323"><position...
      <astroObject name="A2324"><position...
      <astroObject name="A2325"><position...
   </region>
</Universe>

If it is simulated and it is some unclassifyable clump of mass points 
within a cluster:
<universe type="N-body" run="879">
   <GalaxyCluster name="326">
      <AstroObject>
   </GalaxyCluster>
</universe>

Besides having Universe as a top level element we need other 
possibilities: universe, DataCenters,  Filters, astroObject, etc.  One 
chooses the top level element depending on what the catalog is about.

By the way, the fact that Universe and universe have different meanings 
in English is one of several reasons why I disagreed with a standards 
that use capitals to indicate an element.

Ed