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Hi all,

It seems that the CellML specification is unclear on exactly what happens when
initial_value="name"(i.e. a variable name)...

* The name of the initial_value attribute is derived from the fact that, in a
model with only one independent variable, this would generally correspond to
time, and so the value of the initial_value attribute sets the starting
condition for a simulation which progressed from time equals 0.0. The value of
the initial_value attribute may be a real number or a variable. A modeller may
wish to store the initial and boundary conditions in a separate file that is
imported by the current model. See Section 9 for more information on CellML's
import feature.

This really needs some additional prose to specify exactly what CellML
processing software is expected to do.

In particular:
1) Should CellML processing software allow assignment of initial values from
variables which have a computed constant value(as opposed to an initial_value
assignment)? This was brought up at the CellML meeting today, and the rough
consensus was that the specification should be interpreted in this way.

2) Should CellML processing software perform units conversion when copying an
initial_value from variables of different units? e.g. if I have...

<variable name="initial_distance" units="metre" />
<variable name="distance" units="millimetre" initial_value="initial_distance"
/>
<mathml:math>
<apply>
<eq/>
<ci>initial_distance</ci>
<apply><times/>
<cn cellml:units="metre_per_second">0.05</cn>
<cn cellml:units="second">2</cn>
</apply>
</apply>
</mathml:math>

Should a conversion from millmetre to metre be performed? It probably makes
sense to do this, but the CellML specification does not seem to it.

Best regards,
Andrew Miller


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• [cellml-discussion] Spec is unclear on initial_value="name", Andrew Miller, 01/19/2006

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