- From: jonathan.cooper at comlab.ox.ac.uk (Jonathan Cooper)
- Subject: [cellml-discussion] A list of proposed changes to semantics to makein CellML 1.2
- Date: Sat, 22 Dec 2007 07:21:33 +0000
On Sat, Dec 22, 2007 at 11:19:52AM +1300, Poul Nielsen wrote:
>
I think that Jonathan is correct - the concept of 'in' and 'out'
>
does not make sense in a declarative description. One way to remedy
>
this would be to remove the 'public_interface' and
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'private_interface' attributes from the <variable> element and
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replace them with an 'interface' attribute which could assume values
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"public", "private", or "none". This is a pretty fundamental change
>
to the specification but I think that it better reflects the
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declarative intent of CellML model descriptions.
How would that work for a component like B below, which has both a public
and private interface for the same variable?
Jonathan.
>
On 2007 Dec 22, at 03:20, Jonathan Cooper wrote:
>
>
> On Thu, Dec 20, 2007 at 12:30:32AM +0800, David Nickerson wrote:
>
>>> * The current specification says:
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>>> "A variable with either a private_interface or public_interface
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>>> attribute
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>>> value of "in" must be mapped to no more than one other
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>>> variable in the
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>>> model. [ Note that a similar restriction does not apply to
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>>> variables with
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>>> interface values of "out". An output variable can be mapped to
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>>> multiple
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>>> input variables in various components in the current model. ]"
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>>>
>
>>> The problem with this is that it doesn't properly account for
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>>> mappings where a variable is forwarded into an encapsulated
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>>> block. As
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>>> an example, consider the following encapsulation hierarchy (higher
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>>> components encapsulate lower ones)...
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>>>
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>>> A
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>>> |
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>>> B
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>>> / \
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>>> C D
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>>>
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>>> Suppose that component A has, for variable v,
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>>> public_interface="none", private_interface="out", and B has for
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>>> variable v, public_interface="in", private_interface="out"
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>>> (connected to A), and C and D have public_interface="in",
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>>> private_interface="none", both of which are connected to B.
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>>>
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>>> There is no reason why this should not be valid. However, the
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>>> specification contradicts itself on whether this is allowed. On
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>>> one
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>>> hand, because B has private_interface="out", it "can be mapped to
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>>> multiple input variables in various components in the current
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>>> model.", but because it has a public interface of in, it "must be
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>>> mapped to no more than one other variable in the model".
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>>>
>
>>> This can be fixed by firstly defining the interpretation of
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>>> connections and interfaces, and then adding constraints based on
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>>> that which actually describe which connections are allowed to each
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>>> set of variables.
>
>>
>
>> will be interesting to see how such a definition ties in with the
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>> idea
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>> of input variables becoming output variables based on the way the
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>> components are hooked together :)
>
>
>
> Indeed.
>
>
>
> The use of "in" and "out" on interfaces very strongly implies that
>
> connections have a directionality, and this is also reflected in the
>
> quote from the specification above - it assumes that variables are
>
> only
>
> defined in one place, and hence it doesn't make sense to import a
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> variable (via an "in" interface) from multiple locations. It does
>
> however make sense to export a variable to multiple locations, or
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> forward
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> an imported variable to multiple locations (the example Andrew gives).
>
>
>
> If we don't want connections to have directionality, then I think this
>
> requires quite a major change in the specification, even if only to
>
> avoid
>
> user confusion. For example, I would want to deprecate the use of
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> "in"
>
> and "out", and instead allow public_interface="yes" or
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> public_interface="no" (perhaps a synonym for "none") and similarly for
>
> private interfaces. The terms used in the language then reflect the
>
> nature of the interfaces - if connections are bidirectional, then it
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> doesn't make sense to talk of an "in" interface, since it may function
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> either as input or output depending on the other components in the
>
> system.
>
>
>
> Jonathan.
>
>
>
> --
>
> Jonathan Cooper MSN: msn at jonc.me.uk www: jonc.me.uk/
>
>
>
> We are tribbles of Borg. Prepare to be replicated.
>
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>
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>
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>
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>
>
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--
Jonathan Cooper MSN: msn at jonc.me.uk www: jonc.me.uk/
I haven't lost my mind... It's backed up on tape somewhere.
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