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Hi folks,

After reading Alan arguments and Matt's responses, I remain unpersuaded
that we need to change the way the standard units are handled.

By all means, the import mechanism can be used to load sets of unit
definitions that build on top of the standard units, but I see no reason
why the standard units should be imported. They're standard -- that's
the whole point! They're something that model authors and all tools can
rely on.

Also, I believe the SBML spec defines a very similar set of standard
units in the same way (basically the SI units plus a couple of useful
things), so we would be introducing a level of complexity in translation
that doesn't seem useful.

My 2c,
Warren


Matt Halstead wrote:
> Section 5.2.1 of the cellml 1.1 specification
> (http://www.cellml.org/public/specification/20030930/
> cellml_specification.html#tab_units_cellml_units_dictionary) describes
> the dictionary of standard units. Since we now have imports, is there
> any reason not to create a SI base unit library that declares each of
> these units in this table as a base_unit, and which modellers should
> probably import by default?
>
> A case example where this is useful in application development is an
> editor application that forces a user to select a units for each
> variable. If these units in table 2 were represented as a library and
> imported, then we can simplify the method for building units available
> for a variable.
>
> Another use-case is providing a mechanism to curate this table of
> units, we would be free to add new definitions, annotate them with RDF,
> and then argue about them.
>

--
Warren Hedley
Alliance For Cell Signaling
San Diego Supercomputer Center
>From whedley at sdsc.edu Sat Aug 7 04:06:24 2004
From: whedley at sdsc.edu (Warren Hedley)
Date: Sat Aug 7 04:06:31 2004
Subject: [cellml-discussion] base_si_units.xml
In-Reply-To:
<C92B8FBA-E765-11D8-A6DB-000A95B32AC4 AT auckland.ac.nz>
References:
<C92B8FBA-E765-11D8-A6DB-000A95B32AC4 AT auckland.ac.nz>
Message-ID:
<4113AC80.4070107 AT sdsc.edu>

Hi Matt,

Thank you for putting out a sample file to help clarify things.

If you check the dictionary of standard units, you'll note that only 7
are base units, we've added "dimensionless", and then the rest can be
expressed in terms of those units.

I think your definitions file would be much more useful if the derived
units were defined in terms of the base units. This would then relieve
applications from being responsible for knowing how these units are related.

I can barely remember what a Newton or a Joule is, so I'll leave that as
something for you to research :-)

Cheers,
Warren


Matt Halstead wrote:
> Attempt 1 of a general set of SI units for importing.
>
> <?xml version="1.0" encoding="iso-8859-1"?>
> ...
>
> <units name="ampere" base_units="yes"/>
> <units name="farad" base_units="yes"/>
> <units name="katal" base_units="yes"/>
> <units name="lux" base_units="yes"/>
> <units name="pascal" base_units="yes"/>
> <units name="tesla" base_units="yes"/>
> <units name="becquerel" base_units="yes"/>
> <units name="gram" base_units="yes"/>
> <units name="kelvin" base_units="yes"/>
> <units name="meter" base_units="yes"/>
> <units name="radian" base_units="yes"/>
> <units name="volt" base_units="yes"/>
...

--
Warren Hedley
Alliance For Cell Signaling
San Diego Supercomputer Center
>From matt.halstead at auckland.ac.nz Tue Aug 10 17:58:37 2004
From: matt.halstead at auckland.ac.nz (Matt Halstead)
Date: Tue Aug 10 17:59:14 2004
Subject: [cellml-discussion] Import question
Message-ID:
<520FCBCC-EA92-11D8-9F97-000A95B32AC4 AT auckland.ac.nz>

The following paragraph in section 9.2 of the CellML 1.1 specification
leaves me with a question :

(http://www.cellml.org/public/specification/20030930/
cellml_specification.html#sec_import_model)

"The connections are only maintained between the components and their
component trees listed in one <cellml:import> element; therefore, if an
imported component relies on values from other components in the
original model, every component from which it obtains values needs to
be imported."


This implies that the relevant connections are imported, but we have
not said anything about remapping these connections. The importer is
allowed to name the imported components whatever they want; the
implicitly imported connections will be defined using the names from
the imported model. There needs to be a rule, albeit simple, explained
that remaps the connections using the new component names.

cheers
Matt

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• [cellml-discussion] cellml units, Alan Garny, 08/06/2004
  • [cellml-discussion] cellml units, Matt Halstead, 08/06/2004
    • [cellml-discussion] cellml units, Alan Garny, 08/06/2004
      • [cellml-discussion] cellml units, Matt Halstead, 08/07/2004
        • [cellml-discussion] cellml units, Alan Garny, 08/07/2004
  • <Possible follow-up(s)>
  • [cellml-discussion] cellml units, Warren Hedley, 08/07/2004

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