From andrea.preitemartinez at iasf-roma.inaf.it  Wed May  3 01:39:49 2006
From: andrea.preitemartinez at iasf-roma.inaf.it (Andrea Preite Martinez)
Date: Wed, 03 May 2006 10:39:49 +0200
Subject: Call for contributions
Message-ID: <20060503103949.jeefi6cir6sgggc0@webmail.sic.rm.cnr.it>

Dear all,

in 2 weeks from now (thu. 16) we will have our session at the InterOp  
meeting in Victoria.
You can find the preliminary agenda at

http://www.ivoa.net/twiki/bin/view/IVOA/InterOpMay2006UCD

Please feel free to suggest modifications and new contributions!!

Regards

Andrea
===================================================================================
Andrea Preite Martinez                 andrea.preitemartinez at iasf-roma.inaf.it
IASF                                   Tel.IASF:+39.06.4993.4651
Via del Fosso del Cavaliere 100        Tel.CDS :+33.3.90242473
I-00133 Roma                           Cell.1  :+39.320.43.15.383
                                        Cell.2  :+39.339.38.17.355
===================================================================================







From andrea.preitemartinez at iasf-roma.inaf.it  Sun May 14 23:48:36 2006
From: andrea.preitemartinez at iasf-roma.inaf.it (Andrea Preite Martinez)
Date: Mon, 15 May 2006 08:48:36 +0200
Subject: UCD's for simulations
In-Reply-To: <Pine.GSO.4.58.0604142228280.6904@cass25>
References: <ODENKDLEINNEPJOIJLEFAELDCNAA.gerard.lemson@mpe.mpg.de>
	<Pine.GSO.4.58.0604142228280.6904@cass25>
Message-ID: <20060515084836.7xzmd39g4gk0c8ww@webmail.sic.rm.cnr.it>

Dear Laurie,

I've been collecting various proposal for upgrading the list of  
UCD-words, and I'll present these proposal for discussion (including  
yours) during the UCD/Semantic session (thu 18, 9.00-10.30).

The list of proposed modifications and the agenda can be found at
http://ivoa.net/twiki/bin/view/IVOA/InterOpMay2006UCD

Regards,

Andrea
===================================================================================
Andrea Preite Martinez                 andrea.preitemartinez at iasf-roma.inaf.it
IASF                                   Tel.IASF:+39.06.4993.4651
Via del Fosso del Cavaliere 100        Tel.CDS :+33.3.90242473
I-00133 Roma                           Cell.1  :+39.320.43.15.383
                                        Cell.2  :+39.339.38.17.355
===================================================================================


Quoting Laurie Shaw <lds at ast.cam.ac.uk>:

>
> Dear All,
>
> I've recently been experimenting with assigning UCDs to the results of
> some cosmological simulations -- specifically to catalogues of dark
> matter halos and their associated subhalos. In general, i've found
> that the existing UCD tree is able to describe most of the properties of
> these objects that are typically analysed in the literature, albeit with a
> few exceptions.
>
> However, it is not currently possible to describe the properties and
> parameters of the simulations themselves. This includes some input
> physical parameters (i.e. cosmological parameters) that define the
> theoretical context of the simulation, and technical
> parameters that define its size,scope and resolution (e.g number of
> particles, length of simulation box side, gravitational
> softening length, time/redshift of a simulation output).
>
> Therefore, for the latter, I propose a new branch of the UCD tree to
> encompass computatational techniques in astronomy: 'comp'. This
> branch can be used to describe both astrophysical (and cosmological)
> simulations, and data reduction and post-processing algorithms for
> both simulation and observational data. It is roughly a computing
> analogue of the 'instr' branch. For the case of simulations I propose
> the following sub-branches
>
> comp.sim		(computational simulation)
> comp.sim.nbody		(Nbody simulation)
> comp.sim.sph		(Smoothed Particle Hydrodynamics simulation)
> comp.sim.boxside	(Simulation box)
> comp.sim.gravsoft	(gravitational softening)
> comp.sim.particles	(simulation particles (for Nbody and SPH
> simulations))
> comp.sim.snapshot	(output of a simulation box at a particular
> instant)
> comp.sim.grid		(simulation grid (for hydro simulations))
>
> The number of particles in the simulation box, number of grid points,
> particle mass, gravitational softening length and simulation box side
> length would therefore be:
>
> meta.num;comp.sim.particles
> meta.num;comp.sim.grid
> phys.mass;comp.sim.particles
> phys.size;comp.sim.gravsoft
> phys.size;comp.sim.boxside
>
> (For the last two, introduction of a phys.size.length UCD might provide a
> more accurate description.)
>
> The mass of an object in terms of the number of particles it contains:
>
> phys.mass;meta.num;comp.sim.particles
>
> Other possible sub-branches could be
>
> comp.resourse	         (computational resources used in simulation/data
> processing)
> comp.resource.processors (processors used)
> comp.resource.memory	 (total size of a data file)
>
> plus those that are more specific to data-reduction/post-processing of
> observational data.  Algorithms that might apply to both simulated and
> observed data (e.g. smoothing of images or particle densities) would
> be listed directly under the comp branch:
>
> phys.size;comp.smooth
> (or, with the introduction of a phys.size.length UCD:
> phys.size.length;comp.smooth)
>
> Physical Parameters
> ---------------------
> Currently, there exists no UCDs for the main cosmological
> parameters. In terms of simulations, it is very important to be able
> define the assumed cosmology, when interpreting the results. To
> describe these parameters I propose a 'cosmology' sub-branch of
> the phys branch. So,
>
> phys.cosmology		(cosmology)
> phys.cosmology.omega 	(matter/energy density of universe)
> phys.cosmology.hubble 	(hubble constant)
> phys.cosmology.sigma8 	(Normalisation of matter power-spectrum)
>
> and also:
>
> phys.matter.dark 	(dark matter tag)
> phys.matter.baryon 	(baryonic matter tag)
> phys.DarkEnergy 	(dark energy tag)
>
> So, Omega_Lambda, Omega_DM, Omega_baryon would be
>
> phys.cosmology.omega;phys.DarkEnery,
> phys.cosmology.omega;phys.matter.dark
> phys.comsology.omega;phys.matter.baryonic
>
> Now we can also describe the number of dark matter (gas particles) in
> an SPH simulation, or a simulated object (star/galaxy/halo) using:
>
> meta.num;comp.sim.particles;phys.matter.dark(/baryonic)
>
> Furthermore, the mass and radius of dark matter halos in cosmological
> simulations are frequently defined in terms of a virial
> overdensity. Hence a phys.virial UCD would be usefull in specifying
> what is meant by the mass and radius of a halo:
>
> phys.mass;phys.virial (virial mass)
> phys.size.radius;phys.virial (virial radius)
>
> Time in Simulations
> ------------------
> People frequently analyse the output of simulations, or snapshots, at
> a series of different timesteps. This is often quoted in terms of the
> redshift of
> the snapshot. At the moment, redshift exists under the 'src'
> branch. Maybe it might be better under the `phys' branch as it is a
> measure of both distance and time, and can therefore be used to label
> both the distance of observed objects and to label a time-stamp for
> simulation snapshots:
>
> phys.redshift;comp.sim.snapshot
>
> Astrophysical Objects
> --------------------
> Another problem is the listing of astronomical objects types under the
> 'src' branch. This introduces confusion when trying to describe a
> simulated astrophysical object. For example, the first word in
> src.class.galaxy;comp.sim (simulated galaxy) implies that this is an
> observed astrophysical source, the second that it is simulated.
>
> Additionally, objects such as halos and subhalos are not typically
> observed (though i guess people do make estimates of their mass/size
> through
> gravitational lensing). It seems strange to have halo and subhalo
> listed under the src.class sub-branch. I therefore suggest that an
> object branch be introduced in which astrophysical (and theoretical)
> objects can be listed (as also proposed by others on the UCD suggestion
> page):
>
> object.galaxy;comp.sim (a simulated galaxy)
> object.galaxy.spiral;comp.sim (a simulated spiral galaxy)
>
> One example that I encountered of an actual quantity where this was
> useful is describing the mass in substructure, or the number of
> subhalos, in a simulated halo:
>
> phys.mass;object.DMhalo.subhalo
> meta.num;onject.DMhalo.subhalo
>
> It would be great to hear everyones thoughts, or ideas for alternative
> approaches, for all these.
>
> Cheers,
>
> Laurie
>
>
> List of Proposed UCDs
> ---------------------
> comp (computational astronomy)
> comp.sim (simulations)
> comp.sim.nbody (Nbody simulation)
> comp.sim.sph (Smoothed Particle Hydrodynamics simulation)
> comp.sim.boxside (Simulation box)
> comp.sim.gravsoft (gravitational softening)
> comp.sim.particles (simulation particles (for Nbody and SPH simulations))
> comp.sim.snapshot (output of a simulation box at a particular instant)
> comp.sim.grid (simulation grid (for hydro simulations))
> comp.resourse (to describe computational resources used in simulation/data
> processing)
> comp.resource.processors (processors used)
> comp.resource.memory (total size on disk of data)
> (comp.dataReduct ?
> comp.algorithm (general algorithms applied to sim/obs data) )
>
> phys.cosmology
> phys.cosmology.omega (matter/energy density of universe)
> phys.cosmology.hubble (hubble constant)
> phys.cosmology.sigma8 (Normalisation of matter power-spectrum)
> phys.matter.dark (dark matter tag)
> phys.matter.baryon (baryonic matter tag)
> phys.DarkEnergy (dark energy tag)
> phys.virial
> phys.size.length
>
> object  (astophysical object)
> object.planet (planet)
> object.satellite
> object.star   (star)
> object.galaxy (galaxy)
> object.DMhalo (DM halo)
> Object.DMhalo.subhalo (DM subhalo)
> etc
>
>
>






From andrea.preitemartinez at iasf-roma.inaf.it  Sun May 14 23:48:36 2006
From: andrea.preitemartinez at iasf-roma.inaf.it (Andrea Preite Martinez)
Date: Mon, 15 May 2006 08:48:36 +0200
Subject: UCD's for simulations
In-Reply-To: <Pine.GSO.4.58.0604142228280.6904@cass25>
References: <ODENKDLEINNEPJOIJLEFAELDCNAA.gerard.lemson@mpe.mpg.de>
	<Pine.GSO.4.58.0604142228280.6904@cass25>
Message-ID: <20060515084836.7xzmd39g4gk0c8ww@webmail.sic.rm.cnr.it>

Dear Laurie,

I've been collecting various proposal for upgrading the list of  
UCD-words, and I'll present these proposal for discussion (including  
yours) during the UCD/Semantic session (thu 18, 9.00-10.30).

The list of proposed modifications and the agenda can be found at
http://ivoa.net/twiki/bin/view/IVOA/InterOpMay2006UCD

Regards,

Andrea
===================================================================================
Andrea Preite Martinez                 andrea.preitemartinez at iasf-roma.inaf.it
IASF                                   Tel.IASF:+39.06.4993.4651
Via del Fosso del Cavaliere 100        Tel.CDS :+33.3.90242473
I-00133 Roma                           Cell.1  :+39.320.43.15.383
                                        Cell.2  :+39.339.38.17.355
===================================================================================


Quoting Laurie Shaw <lds at ast.cam.ac.uk>:

>
> Dear All,
>
> I've recently been experimenting with assigning UCDs to the results of
> some cosmological simulations -- specifically to catalogues of dark
> matter halos and their associated subhalos. In general, i've found
> that the existing UCD tree is able to describe most of the properties of
> these objects that are typically analysed in the literature, albeit with a
> few exceptions.
>
> However, it is not currently possible to describe the properties and
> parameters of the simulations themselves. This includes some input
> physical parameters (i.e. cosmological parameters) that define the
> theoretical context of the simulation, and technical
> parameters that define its size,scope and resolution (e.g number of
> particles, length of simulation box side, gravitational
> softening length, time/redshift of a simulation output).
>
> Therefore, for the latter, I propose a new branch of the UCD tree to
> encompass computatational techniques in astronomy: 'comp'. This
> branch can be used to describe both astrophysical (and cosmological)
> simulations, and data reduction and post-processing algorithms for
> both simulation and observational data. It is roughly a computing
> analogue of the 'instr' branch. For the case of simulations I propose
> the following sub-branches
>
> comp.sim		(computational simulation)
> comp.sim.nbody		(Nbody simulation)
> comp.sim.sph		(Smoothed Particle Hydrodynamics simulation)
> comp.sim.boxside	(Simulation box)
> comp.sim.gravsoft	(gravitational softening)
> comp.sim.particles	(simulation particles (for Nbody and SPH
> simulations))
> comp.sim.snapshot	(output of a simulation box at a particular
> instant)
> comp.sim.grid		(simulation grid (for hydro simulations))
>
> The number of particles in the simulation box, number of grid points,
> particle mass, gravitational softening length and simulation box side
> length would therefore be:
>
> meta.num;comp.sim.particles
> meta.num;comp.sim.grid
> phys.mass;comp.sim.particles
> phys.size;comp.sim.gravsoft
> phys.size;comp.sim.boxside
>
> (For the last two, introduction of a phys.size.length UCD might provide a
> more accurate description.)
>
> The mass of an object in terms of the number of particles it contains:
>
> phys.mass;meta.num;comp.sim.particles
>
> Other possible sub-branches could be
>
> comp.resourse	         (computational resources used in simulation/data
> processing)
> comp.resource.processors (processors used)
> comp.resource.memory	 (total size of a data file)
>
> plus those that are more specific to data-reduction/post-processing of
> observational data.  Algorithms that might apply to both simulated and
> observed data (e.g. smoothing of images or particle densities) would
> be listed directly under the comp branch:
>
> phys.size;comp.smooth
> (or, with the introduction of a phys.size.length UCD:
> phys.size.length;comp.smooth)
>
> Physical Parameters
> ---------------------
> Currently, there exists no UCDs for the main cosmological
> parameters. In terms of simulations, it is very important to be able
> define the assumed cosmology, when interpreting the results. To
> describe these parameters I propose a 'cosmology' sub-branch of
> the phys branch. So,
>
> phys.cosmology		(cosmology)
> phys.cosmology.omega 	(matter/energy density of universe)
> phys.cosmology.hubble 	(hubble constant)
> phys.cosmology.sigma8 	(Normalisation of matter power-spectrum)
>
> and also:
>
> phys.matter.dark 	(dark matter tag)
> phys.matter.baryon 	(baryonic matter tag)
> phys.DarkEnergy 	(dark energy tag)
>
> So, Omega_Lambda, Omega_DM, Omega_baryon would be
>
> phys.cosmology.omega;phys.DarkEnery,
> phys.cosmology.omega;phys.matter.dark
> phys.comsology.omega;phys.matter.baryonic
>
> Now we can also describe the number of dark matter (gas particles) in
> an SPH simulation, or a simulated object (star/galaxy/halo) using:
>
> meta.num;comp.sim.particles;phys.matter.dark(/baryonic)
>
> Furthermore, the mass and radius of dark matter halos in cosmological
> simulations are frequently defined in terms of a virial
> overdensity. Hence a phys.virial UCD would be usefull in specifying
> what is meant by the mass and radius of a halo:
>
> phys.mass;phys.virial (virial mass)
> phys.size.radius;phys.virial (virial radius)
>
> Time in Simulations
> ------------------
> People frequently analyse the output of simulations, or snapshots, at
> a series of different timesteps. This is often quoted in terms of the
> redshift of
> the snapshot. At the moment, redshift exists under the 'src'
> branch. Maybe it might be better under the `phys' branch as it is a
> measure of both distance and time, and can therefore be used to label
> both the distance of observed objects and to label a time-stamp for
> simulation snapshots:
>
> phys.redshift;comp.sim.snapshot
>
> Astrophysical Objects
> --------------------
> Another problem is the listing of astronomical objects types under the
> 'src' branch. This introduces confusion when trying to describe a
> simulated astrophysical object. For example, the first word in
> src.class.galaxy;comp.sim (simulated galaxy) implies that this is an
> observed astrophysical source, the second that it is simulated.
>
> Additionally, objects such as halos and subhalos are not typically
> observed (though i guess people do make estimates of their mass/size
> through
> gravitational lensing). It seems strange to have halo and subhalo
> listed under the src.class sub-branch. I therefore suggest that an
> object branch be introduced in which astrophysical (and theoretical)
> objects can be listed (as also proposed by others on the UCD suggestion
> page):
>
> object.galaxy;comp.sim (a simulated galaxy)
> object.galaxy.spiral;comp.sim (a simulated spiral galaxy)
>
> One example that I encountered of an actual quantity where this was
> useful is describing the mass in substructure, or the number of
> subhalos, in a simulated halo:
>
> phys.mass;object.DMhalo.subhalo
> meta.num;onject.DMhalo.subhalo
>
> It would be great to hear everyones thoughts, or ideas for alternative
> approaches, for all these.
>
> Cheers,
>
> Laurie
>
>
> List of Proposed UCDs
> ---------------------
> comp (computational astronomy)
> comp.sim (simulations)
> comp.sim.nbody (Nbody simulation)
> comp.sim.sph (Smoothed Particle Hydrodynamics simulation)
> comp.sim.boxside (Simulation box)
> comp.sim.gravsoft (gravitational softening)
> comp.sim.particles (simulation particles (for Nbody and SPH simulations))
> comp.sim.snapshot (output of a simulation box at a particular instant)
> comp.sim.grid (simulation grid (for hydro simulations))
> comp.resourse (to describe computational resources used in simulation/data
> processing)
> comp.resource.processors (processors used)
> comp.resource.memory (total size on disk of data)
> (comp.dataReduct ?
> comp.algorithm (general algorithms applied to sim/obs data) )
>
> phys.cosmology
> phys.cosmology.omega (matter/energy density of universe)
> phys.cosmology.hubble (hubble constant)
> phys.cosmology.sigma8 (Normalisation of matter power-spectrum)
> phys.matter.dark (dark matter tag)
> phys.matter.baryon (baryonic matter tag)
> phys.DarkEnergy (dark energy tag)
> phys.virial
> phys.size.length
>
> object  (astophysical object)
> object.planet (planet)
> object.satellite
> object.star   (star)
> object.galaxy (galaxy)
> object.DMhalo (DM halo)
> Object.DMhalo.subhalo (DM subhalo)
> etc
>
>
>






From jcm at head.cfa.harvard.edu  Thu May 18 11:32:21 2006
From: jcm at head.cfa.harvard.edu (Jonathan McDowell)
Date: Thu, 18 May 2006 14:32:21 -0400 (EDT)
Subject: STC and controlled vocab
Message-ID: <200605181832.k4IIWLIB020873@sothis.cfa.harvard.edu>

Dear Andrea,
 The vocab doc has 3 categories:
 - phenomenon, process or feature
 - object types
 - instruments and methods.
I think we need another one maybe for conventions, or
else extend the def. of category 1 or 3??
Here from STC are some concepts that need I think to be
in the vocab. They are defined in STC, but they are concepts that
will exist more widely than STC and form a controlled vocab that
should probably be controlled by the Semantics and not the DM group...

- Timescales   TT, UTC, TDB, LST, ..
- Reference frames  FK5, LSR, CMB frame, GSE...
- Places in the universe that aren't objects:
     Solar system barycenter
     Observer topocenter
     Local group center of mass
     Center of Neptune  (specifically, as opposed to Neptune in general)
- Coordinate systems:
     galactic, equatorial, ecliptic,  planetographic, planetocentric.

- Units !!!!  Perhaps different from the VO Standard Vocab, but 
 I think the Semantics group is the right place to standardize
 IVOA represenation of unit strings??

  Jonathan


From thomas at astro.umd.edu  Tue May 23 08:00:20 2006
From: thomas at astro.umd.edu (Brian Thomas)
Date: Tue, 23 May 2006 11:00:20 -0400
Subject: Who has responsibility for defining units in IVOA (Was: Re: STC and controlled vocab
In-Reply-To: <200605181832.k4IIWLIB020873@sothis.cfa.harvard.edu>
References: <200605181832.k4IIWLIB020873@sothis.cfa.harvard.edu>
Message-ID: <200605231100.20605.thomas@astro.umd.edu>

On Thursday 18 May 2006 14:32, Jonathan McDowell wrote:
> - Units !!!! ?Perhaps different from the VO Standard Vocab, but 
> ?I think the Semantics group is the right place to standardize
> ?IVOA represenation of unit strings??

	Well, youre the chair of the DM group, so you have the power to decide
	to 'not do' something, but..

	I would have thought this a DM exercise as systems of units are already
	well quantified, and there is little, to no, slipperiness in the meaning
	of, or definition of the units themselves. Furthermore, the real 'issue'
	in units seems to be which representations to choose, and which
	system(s) are allowed rather than 'what units mean'.

	-brian


From thomas at astro.umd.edu  Tue May 23 08:00:20 2006
From: thomas at astro.umd.edu (Brian Thomas)
Date: Tue, 23 May 2006 11:00:20 -0400
Subject: Who has responsibility for defining units in IVOA (Was: Re: STC and controlled vocab
In-Reply-To: <200605181832.k4IIWLIB020873@sothis.cfa.harvard.edu>
References: <200605181832.k4IIWLIB020873@sothis.cfa.harvard.edu>
Message-ID: <200605231100.20605.thomas@astro.umd.edu>

On Thursday 18 May 2006 14:32, Jonathan McDowell wrote:
> - Units !!!! ?Perhaps different from the VO Standard Vocab, but 
> ?I think the Semantics group is the right place to standardize
> ?IVOA represenation of unit strings??

	Well, youre the chair of the DM group, so you have the power to decide
	to 'not do' something, but..

	I would have thought this a DM exercise as systems of units are already
	well quantified, and there is little, to no, slipperiness in the meaning
	of, or definition of the units themselves. Furthermore, the real 'issue'
	in units seems to be which representations to choose, and which
	system(s) are allowed rather than 'what units mean'.

	-brian


From arots at head.cfa.harvard.edu  Tue May 23 08:54:34 2006
From: arots at head.cfa.harvard.edu (Arnold Rots)
Date: Tue, 23 May 2006 11:54:34 -0400 (EDT)
Subject: Who has responsibility for defining units in IVOA (Was: Re: STC
 and controlled vocab
In-Reply-To: <200605231100.20605.thomas@astro.umd.edu>
Message-ID: <200605231554.k4NFsYj4004220@xebec.cfa.harvard.edu>

I agree with Brian and I'm not so sure about other parts, either.
The list of the semantics group dealt with things that fall outside
the purview of IVOA standards.
A significant part of establishing standards is defining semantics.
Semantics that define standards should be, well, defined in those
standards, or else the you put the responsibility for all standards on
the semantics group.
It may be helpful for the semantics group to refer to the semantics
defined in standard documents, but that's a different issue.

So, I'd leave units in DM and coordinate-related stuff in STC...

  - Arnold

Brian Thomas wrote:
[ Charset UTF-8 unsupported, converting... ]
> On Thursday 18 May 2006 14:32, Jonathan McDowell wrote:
> > - Units !!!! ?Perhaps different from the VO Standard Vocab, but 
> > ?I think the Semantics group is the right place to standardize
> > ?IVOA represenation of unit strings??
> 
> 	Well, youre the chair of the DM group, so you have the power to decide
> 	to 'not do' something, but..
> 
> 	I would have thought this a DM exercise as systems of units are already
> 	well quantified, and there is little, to no, slipperiness in the meaning
> 	of, or definition of the units themselves. Furthermore, the real 'issue'
> 	in units seems to be which representations to choose, and which
> 	system(s) are allowed rather than 'what units mean'.
> 
> 	-brian
> 
> 
--------------------------------------------------------------------------
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
USA                                     http://hea-www.harvard.edu/~arots/
--------------------------------------------------------------------------


From arots at head.cfa.harvard.edu  Tue May 23 08:54:34 2006
From: arots at head.cfa.harvard.edu (Arnold Rots)
Date: Tue, 23 May 2006 11:54:34 -0400 (EDT)
Subject: Who has responsibility for defining units in IVOA (Was: Re: STC
 and controlled vocab
In-Reply-To: <200605231100.20605.thomas@astro.umd.edu>
Message-ID: <200605231554.k4NFsYj4004220@xebec.cfa.harvard.edu>

I agree with Brian and I'm not so sure about other parts, either.
The list of the semantics group dealt with things that fall outside
the purview of IVOA standards.
A significant part of establishing standards is defining semantics.
Semantics that define standards should be, well, defined in those
standards, or else the you put the responsibility for all standards on
the semantics group.
It may be helpful for the semantics group to refer to the semantics
defined in standard documents, but that's a different issue.

So, I'd leave units in DM and coordinate-related stuff in STC...

  - Arnold

Brian Thomas wrote:
[ Charset UTF-8 unsupported, converting... ]
> On Thursday 18 May 2006 14:32, Jonathan McDowell wrote:
> > - Units !!!! ?Perhaps different from the VO Standard Vocab, but 
> > ?I think the Semantics group is the right place to standardize
> > ?IVOA represenation of unit strings??
> 
> 	Well, youre the chair of the DM group, so you have the power to decide
> 	to 'not do' something, but..
> 
> 	I would have thought this a DM exercise as systems of units are already
> 	well quantified, and there is little, to no, slipperiness in the meaning
> 	of, or definition of the units themselves. Furthermore, the real 'issue'
> 	in units seems to be which representations to choose, and which
> 	system(s) are allowed rather than 'what units mean'.
> 
> 	-brian
> 
> 
--------------------------------------------------------------------------
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
USA                                     http://hea-www.harvard.edu/~arots/
--------------------------------------------------------------------------


From andrea.preitemartinez at iasf-roma.inaf.it  Wed May  3 01:39:49 2006
From: andrea.preitemartinez at iasf-roma.inaf.it (Andrea Preite Martinez)
Date: Wed, 03 May 2006 10:39:49 +0200
Subject: Call for contributions
Message-ID: <20060503103949.jeefi6cir6sgggc0@webmail.sic.rm.cnr.it>

Dear all,

in 2 weeks from now (thu. 16) we will have our session at the InterOp  
meeting in Victoria.
You can find the preliminary agenda at

http://www.ivoa.net/twiki/bin/view/IVOA/InterOpMay2006UCD

Please feel free to suggest modifications and new contributions!!

Regards

Andrea
===================================================================================
Andrea Preite Martinez                 andrea.preitemartinez at iasf-roma.inaf.it
IASF                                   Tel.IASF:+39.06.4993.4651
Via del Fosso del Cavaliere 100        Tel.CDS :+33.3.90242473
I-00133 Roma                           Cell.1  :+39.320.43.15.383
                                        Cell.2  :+39.339.38.17.355
===================================================================================







From andrea.preitemartinez at iasf-roma.inaf.it  Sun May 14 23:48:36 2006
From: andrea.preitemartinez at iasf-roma.inaf.it (Andrea Preite Martinez)
Date: Mon, 15 May 2006 08:48:36 +0200
Subject: UCD's for simulations
In-Reply-To: <Pine.GSO.4.58.0604142228280.6904@cass25>
References: <ODENKDLEINNEPJOIJLEFAELDCNAA.gerard.lemson@mpe.mpg.de>
	<Pine.GSO.4.58.0604142228280.6904@cass25>
Message-ID: <20060515084836.7xzmd39g4gk0c8ww@webmail.sic.rm.cnr.it>

Dear Laurie,

I've been collecting various proposal for upgrading the list of  
UCD-words, and I'll present these proposal for discussion (including  
yours) during the UCD/Semantic session (thu 18, 9.00-10.30).

The list of proposed modifications and the agenda can be found at
http://ivoa.net/twiki/bin/view/IVOA/InterOpMay2006UCD

Regards,

Andrea
===================================================================================
Andrea Preite Martinez                 andrea.preitemartinez at iasf-roma.inaf.it
IASF                                   Tel.IASF:+39.06.4993.4651
Via del Fosso del Cavaliere 100        Tel.CDS :+33.3.90242473
I-00133 Roma                           Cell.1  :+39.320.43.15.383
                                        Cell.2  :+39.339.38.17.355
===================================================================================


Quoting Laurie Shaw <lds at ast.cam.ac.uk>:

>
> Dear All,
>
> I've recently been experimenting with assigning UCDs to the results of
> some cosmological simulations -- specifically to catalogues of dark
> matter halos and their associated subhalos. In general, i've found
> that the existing UCD tree is able to describe most of the properties of
> these objects that are typically analysed in the literature, albeit with a
> few exceptions.
>
> However, it is not currently possible to describe the properties and
> parameters of the simulations themselves. This includes some input
> physical parameters (i.e. cosmological parameters) that define the
> theoretical context of the simulation, and technical
> parameters that define its size,scope and resolution (e.g number of
> particles, length of simulation box side, gravitational
> softening length, time/redshift of a simulation output).
>
> Therefore, for the latter, I propose a new branch of the UCD tree to
> encompass computatational techniques in astronomy: 'comp'. This
> branch can be used to describe both astrophysical (and cosmological)
> simulations, and data reduction and post-processing algorithms for
> both simulation and observational data. It is roughly a computing
> analogue of the 'instr' branch. For the case of simulations I propose
> the following sub-branches
>
> comp.sim		(computational simulation)
> comp.sim.nbody		(Nbody simulation)
> comp.sim.sph		(Smoothed Particle Hydrodynamics simulation)
> comp.sim.boxside	(Simulation box)
> comp.sim.gravsoft	(gravitational softening)
> comp.sim.particles	(simulation particles (for Nbody and SPH
> simulations))
> comp.sim.snapshot	(output of a simulation box at a particular
> instant)
> comp.sim.grid		(simulation grid (for hydro simulations))
>
> The number of particles in the simulation box, number of grid points,
> particle mass, gravitational softening length and simulation box side
> length would therefore be:
>
> meta.num;comp.sim.particles
> meta.num;comp.sim.grid
> phys.mass;comp.sim.particles
> phys.size;comp.sim.gravsoft
> phys.size;comp.sim.boxside
>
> (For the last two, introduction of a phys.size.length UCD might provide a
> more accurate description.)
>
> The mass of an object in terms of the number of particles it contains:
>
> phys.mass;meta.num;comp.sim.particles
>
> Other possible sub-branches could be
>
> comp.resourse	         (computational resources used in simulation/data
> processing)
> comp.resource.processors (processors used)
> comp.resource.memory	 (total size of a data file)
>
> plus those that are more specific to data-reduction/post-processing of
> observational data.  Algorithms that might apply to both simulated and
> observed data (e.g. smoothing of images or particle densities) would
> be listed directly under the comp branch:
>
> phys.size;comp.smooth
> (or, with the introduction of a phys.size.length UCD:
> phys.size.length;comp.smooth)
>
> Physical Parameters
> ---------------------
> Currently, there exists no UCDs for the main cosmological
> parameters. In terms of simulations, it is very important to be able
> define the assumed cosmology, when interpreting the results. To
> describe these parameters I propose a 'cosmology' sub-branch of
> the phys branch. So,
>
> phys.cosmology		(cosmology)
> phys.cosmology.omega 	(matter/energy density of universe)
> phys.cosmology.hubble 	(hubble constant)
> phys.cosmology.sigma8 	(Normalisation of matter power-spectrum)
>
> and also:
>
> phys.matter.dark 	(dark matter tag)
> phys.matter.baryon 	(baryonic matter tag)
> phys.DarkEnergy 	(dark energy tag)
>
> So, Omega_Lambda, Omega_DM, Omega_baryon would be
>
> phys.cosmology.omega;phys.DarkEnery,
> phys.cosmology.omega;phys.matter.dark
> phys.comsology.omega;phys.matter.baryonic
>
> Now we can also describe the number of dark matter (gas particles) in
> an SPH simulation, or a simulated object (star/galaxy/halo) using:
>
> meta.num;comp.sim.particles;phys.matter.dark(/baryonic)
>
> Furthermore, the mass and radius of dark matter halos in cosmological
> simulations are frequently defined in terms of a virial
> overdensity. Hence a phys.virial UCD would be usefull in specifying
> what is meant by the mass and radius of a halo:
>
> phys.mass;phys.virial (virial mass)
> phys.size.radius;phys.virial (virial radius)
>
> Time in Simulations
> ------------------
> People frequently analyse the output of simulations, or snapshots, at
> a series of different timesteps. This is often quoted in terms of the
> redshift of
> the snapshot. At the moment, redshift exists under the 'src'
> branch. Maybe it might be better under the `phys' branch as it is a
> measure of both distance and time, and can therefore be used to label
> both the distance of observed objects and to label a time-stamp for
> simulation snapshots:
>
> phys.redshift;comp.sim.snapshot
>
> Astrophysical Objects
> --------------------
> Another problem is the listing of astronomical objects types under the
> 'src' branch. This introduces confusion when trying to describe a
> simulated astrophysical object. For example, the first word in
> src.class.galaxy;comp.sim (simulated galaxy) implies that this is an
> observed astrophysical source, the second that it is simulated.
>
> Additionally, objects such as halos and subhalos are not typically
> observed (though i guess people do make estimates of their mass/size
> through
> gravitational lensing). It seems strange to have halo and subhalo
> listed under the src.class sub-branch. I therefore suggest that an
> object branch be introduced in which astrophysical (and theoretical)
> objects can be listed (as also proposed by others on the UCD suggestion
> page):
>
> object.galaxy;comp.sim (a simulated galaxy)
> object.galaxy.spiral;comp.sim (a simulated spiral galaxy)
>
> One example that I encountered of an actual quantity where this was
> useful is describing the mass in substructure, or the number of
> subhalos, in a simulated halo:
>
> phys.mass;object.DMhalo.subhalo
> meta.num;onject.DMhalo.subhalo
>
> It would be great to hear everyones thoughts, or ideas for alternative
> approaches, for all these.
>
> Cheers,
>
> Laurie
>
>
> List of Proposed UCDs
> ---------------------
> comp (computational astronomy)
> comp.sim (simulations)
> comp.sim.nbody (Nbody simulation)
> comp.sim.sph (Smoothed Particle Hydrodynamics simulation)
> comp.sim.boxside (Simulation box)
> comp.sim.gravsoft (gravitational softening)
> comp.sim.particles (simulation particles (for Nbody and SPH simulations))
> comp.sim.snapshot (output of a simulation box at a particular instant)
> comp.sim.grid (simulation grid (for hydro simulations))
> comp.resourse (to describe computational resources used in simulation/data
> processing)
> comp.resource.processors (processors used)
> comp.resource.memory (total size on disk of data)
> (comp.dataReduct ?
> comp.algorithm (general algorithms applied to sim/obs data) )
>
> phys.cosmology
> phys.cosmology.omega (matter/energy density of universe)
> phys.cosmology.hubble (hubble constant)
> phys.cosmology.sigma8 (Normalisation of matter power-spectrum)
> phys.matter.dark (dark matter tag)
> phys.matter.baryon (baryonic matter tag)
> phys.DarkEnergy (dark energy tag)
> phys.virial
> phys.size.length
>
> object  (astophysical object)
> object.planet (planet)
> object.satellite
> object.star   (star)
> object.galaxy (galaxy)
> object.DMhalo (DM halo)
> Object.DMhalo.subhalo (DM subhalo)
> etc
>
>
>






From andrea.preitemartinez at iasf-roma.inaf.it  Sun May 14 23:48:36 2006
From: andrea.preitemartinez at iasf-roma.inaf.it (Andrea Preite Martinez)
Date: Mon, 15 May 2006 08:48:36 +0200
Subject: UCD's for simulations
In-Reply-To: <Pine.GSO.4.58.0604142228280.6904@cass25>
References: <ODENKDLEINNEPJOIJLEFAELDCNAA.gerard.lemson@mpe.mpg.de>
	<Pine.GSO.4.58.0604142228280.6904@cass25>
Message-ID: <20060515084836.7xzmd39g4gk0c8ww@webmail.sic.rm.cnr.it>

Dear Laurie,

I've been collecting various proposal for upgrading the list of  
UCD-words, and I'll present these proposal for discussion (including  
yours) during the UCD/Semantic session (thu 18, 9.00-10.30).

The list of proposed modifications and the agenda can be found at
http://ivoa.net/twiki/bin/view/IVOA/InterOpMay2006UCD

Regards,

Andrea
===================================================================================
Andrea Preite Martinez                 andrea.preitemartinez at iasf-roma.inaf.it
IASF                                   Tel.IASF:+39.06.4993.4651
Via del Fosso del Cavaliere 100        Tel.CDS :+33.3.90242473
I-00133 Roma                           Cell.1  :+39.320.43.15.383
                                        Cell.2  :+39.339.38.17.355
===================================================================================


Quoting Laurie Shaw <lds at ast.cam.ac.uk>:

>
> Dear All,
>
> I've recently been experimenting with assigning UCDs to the results of
> some cosmological simulations -- specifically to catalogues of dark
> matter halos and their associated subhalos. In general, i've found
> that the existing UCD tree is able to describe most of the properties of
> these objects that are typically analysed in the literature, albeit with a
> few exceptions.
>
> However, it is not currently possible to describe the properties and
> parameters of the simulations themselves. This includes some input
> physical parameters (i.e. cosmological parameters) that define the
> theoretical context of the simulation, and technical
> parameters that define its size,scope and resolution (e.g number of
> particles, length of simulation box side, gravitational
> softening length, time/redshift of a simulation output).
>
> Therefore, for the latter, I propose a new branch of the UCD tree to
> encompass computatational techniques in astronomy: 'comp'. This
> branch can be used to describe both astrophysical (and cosmological)
> simulations, and data reduction and post-processing algorithms for
> both simulation and observational data. It is roughly a computing
> analogue of the 'instr' branch. For the case of simulations I propose
> the following sub-branches
>
> comp.sim		(computational simulation)
> comp.sim.nbody		(Nbody simulation)
> comp.sim.sph		(Smoothed Particle Hydrodynamics simulation)
> comp.sim.boxside	(Simulation box)
> comp.sim.gravsoft	(gravitational softening)
> comp.sim.particles	(simulation particles (for Nbody and SPH
> simulations))
> comp.sim.snapshot	(output of a simulation box at a particular
> instant)
> comp.sim.grid		(simulation grid (for hydro simulations))
>
> The number of particles in the simulation box, number of grid points,
> particle mass, gravitational softening length and simulation box side
> length would therefore be:
>
> meta.num;comp.sim.particles
> meta.num;comp.sim.grid
> phys.mass;comp.sim.particles
> phys.size;comp.sim.gravsoft
> phys.size;comp.sim.boxside
>
> (For the last two, introduction of a phys.size.length UCD might provide a
> more accurate description.)
>
> The mass of an object in terms of the number of particles it contains:
>
> phys.mass;meta.num;comp.sim.particles
>
> Other possible sub-branches could be
>
> comp.resourse	         (computational resources used in simulation/data
> processing)
> comp.resource.processors (processors used)
> comp.resource.memory	 (total size of a data file)
>
> plus those that are more specific to data-reduction/post-processing of
> observational data.  Algorithms that might apply to both simulated and
> observed data (e.g. smoothing of images or particle densities) would
> be listed directly under the comp branch:
>
> phys.size;comp.smooth
> (or, with the introduction of a phys.size.length UCD:
> phys.size.length;comp.smooth)
>
> Physical Parameters
> ---------------------
> Currently, there exists no UCDs for the main cosmological
> parameters. In terms of simulations, it is very important to be able
> define the assumed cosmology, when interpreting the results. To
> describe these parameters I propose a 'cosmology' sub-branch of
> the phys branch. So,
>
> phys.cosmology		(cosmology)
> phys.cosmology.omega 	(matter/energy density of universe)
> phys.cosmology.hubble 	(hubble constant)
> phys.cosmology.sigma8 	(Normalisation of matter power-spectrum)
>
> and also:
>
> phys.matter.dark 	(dark matter tag)
> phys.matter.baryon 	(baryonic matter tag)
> phys.DarkEnergy 	(dark energy tag)
>
> So, Omega_Lambda, Omega_DM, Omega_baryon would be
>
> phys.cosmology.omega;phys.DarkEnery,
> phys.cosmology.omega;phys.matter.dark
> phys.comsology.omega;phys.matter.baryonic
>
> Now we can also describe the number of dark matter (gas particles) in
> an SPH simulation, or a simulated object (star/galaxy/halo) using:
>
> meta.num;comp.sim.particles;phys.matter.dark(/baryonic)
>
> Furthermore, the mass and radius of dark matter halos in cosmological
> simulations are frequently defined in terms of a virial
> overdensity. Hence a phys.virial UCD would be usefull in specifying
> what is meant by the mass and radius of a halo:
>
> phys.mass;phys.virial (virial mass)
> phys.size.radius;phys.virial (virial radius)
>
> Time in Simulations
> ------------------
> People frequently analyse the output of simulations, or snapshots, at
> a series of different timesteps. This is often quoted in terms of the
> redshift of
> the snapshot. At the moment, redshift exists under the 'src'
> branch. Maybe it might be better under the `phys' branch as it is a
> measure of both distance and time, and can therefore be used to label
> both the distance of observed objects and to label a time-stamp for
> simulation snapshots:
>
> phys.redshift;comp.sim.snapshot
>
> Astrophysical Objects
> --------------------
> Another problem is the listing of astronomical objects types under the
> 'src' branch. This introduces confusion when trying to describe a
> simulated astrophysical object. For example, the first word in
> src.class.galaxy;comp.sim (simulated galaxy) implies that this is an
> observed astrophysical source, the second that it is simulated.
>
> Additionally, objects such as halos and subhalos are not typically
> observed (though i guess people do make estimates of their mass/size
> through
> gravitational lensing). It seems strange to have halo and subhalo
> listed under the src.class sub-branch. I therefore suggest that an
> object branch be introduced in which astrophysical (and theoretical)
> objects can be listed (as also proposed by others on the UCD suggestion
> page):
>
> object.galaxy;comp.sim (a simulated galaxy)
> object.galaxy.spiral;comp.sim (a simulated spiral galaxy)
>
> One example that I encountered of an actual quantity where this was
> useful is describing the mass in substructure, or the number of
> subhalos, in a simulated halo:
>
> phys.mass;object.DMhalo.subhalo
> meta.num;onject.DMhalo.subhalo
>
> It would be great to hear everyones thoughts, or ideas for alternative
> approaches, for all these.
>
> Cheers,
>
> Laurie
>
>
> List of Proposed UCDs
> ---------------------
> comp (computational astronomy)
> comp.sim (simulations)
> comp.sim.nbody (Nbody simulation)
> comp.sim.sph (Smoothed Particle Hydrodynamics simulation)
> comp.sim.boxside (Simulation box)
> comp.sim.gravsoft (gravitational softening)
> comp.sim.particles (simulation particles (for Nbody and SPH simulations))
> comp.sim.snapshot (output of a simulation box at a particular instant)
> comp.sim.grid (simulation grid (for hydro simulations))
> comp.resourse (to describe computational resources used in simulation/data
> processing)
> comp.resource.processors (processors used)
> comp.resource.memory (total size on disk of data)
> (comp.dataReduct ?
> comp.algorithm (general algorithms applied to sim/obs data) )
>
> phys.cosmology
> phys.cosmology.omega (matter/energy density of universe)
> phys.cosmology.hubble (hubble constant)
> phys.cosmology.sigma8 (Normalisation of matter power-spectrum)
> phys.matter.dark (dark matter tag)
> phys.matter.baryon (baryonic matter tag)
> phys.DarkEnergy (dark energy tag)
> phys.virial
> phys.size.length
>
> object  (astophysical object)
> object.planet (planet)
> object.satellite
> object.star   (star)
> object.galaxy (galaxy)
> object.DMhalo (DM halo)
> Object.DMhalo.subhalo (DM subhalo)
> etc
>
>
>






From jcm at head.cfa.harvard.edu  Thu May 18 11:32:21 2006
From: jcm at head.cfa.harvard.edu (Jonathan McDowell)
Date: Thu, 18 May 2006 14:32:21 -0400 (EDT)
Subject: STC and controlled vocab
Message-ID: <200605181832.k4IIWLIB020873@sothis.cfa.harvard.edu>

Dear Andrea,
 The vocab doc has 3 categories:
 - phenomenon, process or feature
 - object types
 - instruments and methods.
I think we need another one maybe for conventions, or
else extend the def. of category 1 or 3??
Here from STC are some concepts that need I think to be
in the vocab. They are defined in STC, but they are concepts that
will exist more widely than STC and form a controlled vocab that
should probably be controlled by the Semantics and not the DM group...

- Timescales   TT, UTC, TDB, LST, ..
- Reference frames  FK5, LSR, CMB frame, GSE...
- Places in the universe that aren't objects:
     Solar system barycenter
     Observer topocenter
     Local group center of mass
     Center of Neptune  (specifically, as opposed to Neptune in general)
- Coordinate systems:
     galactic, equatorial, ecliptic,  planetographic, planetocentric.

- Units !!!!  Perhaps different from the VO Standard Vocab, but 
 I think the Semantics group is the right place to standardize
 IVOA represenation of unit strings??

  Jonathan


From thomas at astro.umd.edu  Tue May 23 08:00:20 2006
From: thomas at astro.umd.edu (Brian Thomas)
Date: Tue, 23 May 2006 11:00:20 -0400
Subject: Who has responsibility for defining units in IVOA (Was: Re: STC and controlled vocab
In-Reply-To: <200605181832.k4IIWLIB020873@sothis.cfa.harvard.edu>
References: <200605181832.k4IIWLIB020873@sothis.cfa.harvard.edu>
Message-ID: <200605231100.20605.thomas@astro.umd.edu>

On Thursday 18 May 2006 14:32, Jonathan McDowell wrote:
> - Units !!!! ?Perhaps different from the VO Standard Vocab, but 
> ?I think the Semantics group is the right place to standardize
> ?IVOA represenation of unit strings??

	Well, youre the chair of the DM group, so you have the power to decide
	to 'not do' something, but..

	I would have thought this a DM exercise as systems of units are already
	well quantified, and there is little, to no, slipperiness in the meaning
	of, or definition of the units themselves. Furthermore, the real 'issue'
	in units seems to be which representations to choose, and which
	system(s) are allowed rather than 'what units mean'.

	-brian


From thomas at astro.umd.edu  Tue May 23 08:00:20 2006
From: thomas at astro.umd.edu (Brian Thomas)
Date: Tue, 23 May 2006 11:00:20 -0400
Subject: Who has responsibility for defining units in IVOA (Was: Re: STC and controlled vocab
In-Reply-To: <200605181832.k4IIWLIB020873@sothis.cfa.harvard.edu>
References: <200605181832.k4IIWLIB020873@sothis.cfa.harvard.edu>
Message-ID: <200605231100.20605.thomas@astro.umd.edu>

On Thursday 18 May 2006 14:32, Jonathan McDowell wrote:
> - Units !!!! ?Perhaps different from the VO Standard Vocab, but 
> ?I think the Semantics group is the right place to standardize
> ?IVOA represenation of unit strings??

	Well, youre the chair of the DM group, so you have the power to decide
	to 'not do' something, but..

	I would have thought this a DM exercise as systems of units are already
	well quantified, and there is little, to no, slipperiness in the meaning
	of, or definition of the units themselves. Furthermore, the real 'issue'
	in units seems to be which representations to choose, and which
	system(s) are allowed rather than 'what units mean'.

	-brian


From arots at head.cfa.harvard.edu  Tue May 23 08:54:34 2006
From: arots at head.cfa.harvard.edu (Arnold Rots)
Date: Tue, 23 May 2006 11:54:34 -0400 (EDT)
Subject: Who has responsibility for defining units in IVOA (Was: Re: STC
 and controlled vocab
In-Reply-To: <200605231100.20605.thomas@astro.umd.edu>
Message-ID: <200605231554.k4NFsYj4004220@xebec.cfa.harvard.edu>

I agree with Brian and I'm not so sure about other parts, either.
The list of the semantics group dealt with things that fall outside
the purview of IVOA standards.
A significant part of establishing standards is defining semantics.
Semantics that define standards should be, well, defined in those
standards, or else the you put the responsibility for all standards on
the semantics group.
It may be helpful for the semantics group to refer to the semantics
defined in standard documents, but that's a different issue.

So, I'd leave units in DM and coordinate-related stuff in STC...

  - Arnold

Brian Thomas wrote:
[ Charset UTF-8 unsupported, converting... ]
> On Thursday 18 May 2006 14:32, Jonathan McDowell wrote:
> > - Units !!!! ?Perhaps different from the VO Standard Vocab, but 
> > ?I think the Semantics group is the right place to standardize
> > ?IVOA represenation of unit strings??
> 
> 	Well, youre the chair of the DM group, so you have the power to decide
> 	to 'not do' something, but..
> 
> 	I would have thought this a DM exercise as systems of units are already
> 	well quantified, and there is little, to no, slipperiness in the meaning
> 	of, or definition of the units themselves. Furthermore, the real 'issue'
> 	in units seems to be which representations to choose, and which
> 	system(s) are allowed rather than 'what units mean'.
> 
> 	-brian
> 
> 
--------------------------------------------------------------------------
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
USA                                     http://hea-www.harvard.edu/~arots/
--------------------------------------------------------------------------


From arots at head.cfa.harvard.edu  Tue May 23 08:54:34 2006
From: arots at head.cfa.harvard.edu (Arnold Rots)
Date: Tue, 23 May 2006 11:54:34 -0400 (EDT)
Subject: Who has responsibility for defining units in IVOA (Was: Re: STC
 and controlled vocab
In-Reply-To: <200605231100.20605.thomas@astro.umd.edu>
Message-ID: <200605231554.k4NFsYj4004220@xebec.cfa.harvard.edu>

I agree with Brian and I'm not so sure about other parts, either.
The list of the semantics group dealt with things that fall outside
the purview of IVOA standards.
A significant part of establishing standards is defining semantics.
Semantics that define standards should be, well, defined in those
standards, or else the you put the responsibility for all standards on
the semantics group.
It may be helpful for the semantics group to refer to the semantics
defined in standard documents, but that's a different issue.

So, I'd leave units in DM and coordinate-related stuff in STC...

  - Arnold

Brian Thomas wrote:
[ Charset UTF-8 unsupported, converting... ]
> On Thursday 18 May 2006 14:32, Jonathan McDowell wrote:
> > - Units !!!! ?Perhaps different from the VO Standard Vocab, but 
> > ?I think the Semantics group is the right place to standardize
> > ?IVOA represenation of unit strings??
> 
> 	Well, youre the chair of the DM group, so you have the power to decide
> 	to 'not do' something, but..
> 
> 	I would have thought this a DM exercise as systems of units are already
> 	well quantified, and there is little, to no, slipperiness in the meaning
> 	of, or definition of the units themselves. Furthermore, the real 'issue'
> 	in units seems to be which representations to choose, and which
> 	system(s) are allowed rather than 'what units mean'.
> 
> 	-brian
> 
> 
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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
USA                                     http://hea-www.harvard.edu/~arots/
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