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David Nickerson wrote:
>> ------- Additional Comments from Andrew Miller <ak.miller at
>> auckland.ac.nz>
>> Section 3.2.4 of CellML 1.1 states, in the second sentence of the second
>> paragraph: "Only one connection may be created between any given pair of
>> components in a model".
>>
>> This is a fairly pointless restriction from all fronts:
>> * From a model authors perspective, it creates a burden on the author to
>> consolidate all their connections which may have been created for different
>> purposes, and current model authors claim that such consolidation is time
>> consuming and error prone.
>>
>
> I'm not sure why this is the case. I much prefer to know that in any
> given model there is only one connection between two particular
> components and that is the *only* place I need to look to add, remove,
> or correct variable connections. If you allow multiple connections
> between the same components then it becomes much more difficult to
> locate extraneous connections, or perhaps software would simply use the
> first (or last) defined connection and leave an author bewildered when
> there model edits have no effect due to a missed connection element earlier.
>
> I'm really not sure who you mean by "current model authors"? But I
> consider such consolidation to be much less time consuming when editing
> complicated models and, as mentioned above, much less error prone.
>

Jonna, James, and Catherine all agreed on this, although as you have now
revealed, this is obviously not a unanimous view amongst model authors.

With regards to the 'would simply use the first (or last) defined
connection and leave an author bewildered when there model edits have
no effect due to a missed connection element earlier' issue, I think we
can add clarifying text to make it absolutely clear that the correct
interpretation is to take the union of all the variable pairs being
connected (we need to find a clearer wording for this, because this
could be confusing in the case where component_1 and component_2 are
reversed, in which case the corresponding variables should of course be
reversed).

>
>> * From a model readability perspective, it is also burdensome because
>> connections between variables may not be in a logical order (this is less
>> of an
>> issue if tools are used, but the point still holds).
>>
>
> I'm not sure the specification should be designed to make the XML
> serialization look pretty - which is what you are saying here, right? If
> you want this to hold then you would need to add rules such that
> software is not allowed to change the order of the XML elements in a
> serialized document.
>

I think that allowing inputs to look pretty is different to forcing it
to look pretty. I don't think we should force all output generated by
tools to look pretty, but allowing authors who like to work from the XML
to input their models in a readable way is still a valid goal.

>
>> * Implementation experience suggests that it is no harder to allow
>> multiple
>> connections between the same pair of components when writing simulation
>> software, but the extra constraint imposes more work on developers when
>> writing
>> tools which try to validate the model.
>>
>
> This seems to be a good reason to keep the rule as it is. Given there is
> already a sever lack of CellML validation tools it seems a bad idea to
> be making it more difficult for people to write such tools.
>
I don't follow. Removing the constraint should make life easier for
validation tools - it is one less thing they have to check.

Best regards,
Andrew

>
> So, I guess what I'm saying is that I object to including this in CellML
> 1.2 - at the very least more discussion is needed to convince me this
> should be done at all. So far I'm seeing one strong reason not to change
> and no reason supporting the change...
>
>
> Andre.
> _______________________________________________
> cellml-discussion mailing list
> cellml-discussion at cellml.org
> http://www.cellml.org/mailman/listinfo/cellml-discussion
>

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• [cellml-discussion] Include_in_CellML_1.2 requested: [Tracker Item 153] Allow multiple connections between the same pair of components, cellml-tracker at cellml.org, 08/29/2007
  • [cellml-discussion] Include_in_CellML_1.2 requested: [Tracker Item 153] Allow multiple connections between the same pair of components, Andrew Miller, 08/29/2007
    • [cellml-discussion] Include_in_CellML_1.2 requested: [Tracker Item 153] Allow multiple connections between the same pair of components, Alan Garny, 08/29/2007
    • [cellml-discussion] Include_in_CellML_1.2 requested: [Tracker Item 153] Allow multiple connections between the same pair of components, Matt, 08/31/2007
  • [cellml-discussion] Include_in_CellML_1.2 requested: [Tracker Item153] Allow multiple connections between the same pair of components, David Nickerson, 08/29/2007
    • [cellml-discussion] Include_in_CellML_1.2 requested: [Tracker Item153] Allow multiple connections between the same pair of components, Andrew Miller, 08/29/2007
      • [cellml-discussion] Include_in_CellML_1.2 requested: [TrackerItem153] Allow multiple connections between the same pair of components, David Nickerson, 08/29/2007
        • [cellml-discussion] Include_in_CellML_1.2 requested: [TrackerItem153] Allow multiple connections between the same pair of components, Jonathan Cooper, 08/31/2007
    • [cellml-discussion] Include_in_CellML_1.2 requested: [Tracker Item153] Allow multiple connections between the same pair of components, Jonna Terkildsen, 08/29/2007
      • [cellml-discussion] Include_in_CellML_1.2 requested: [TrackerItem153] Allow multiple connections between the same pair of components, David Nickerson, 08/29/2007

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