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Please clarify the name of the attribute "previous" in Discrete time state #853

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clagms opened this issue Mar 19, 2020 · 3 comments · May be fixed by #866
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Please clarify the name of the attribute "previous" in Discrete time state #853

clagms opened this issue Mar 19, 2020 · 3 comments · May be fixed by #866

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@clagms
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@clagms clagms commented Mar 19, 2020

This issue comes as a result of a discussion on the solution to #738 .
The name "previous" conveys little meaning as to what this attribute should contain.

In the standard, it says: "Discrete-time states are listed in the ModelStructure and have the variable xml-attribute previous referring to the variable holding the previous value of the state."
I guess that "previous value" means the value of the discrete time state at the previous tick (in the same sense that $x_{j-1}$ refers to the previous value of $x_j$).
Is that correct?

Or does "previous" mean the value at the previous super dense time instant?

@clagms clagms changed the title Please clarify the name of the attribute "previous" in Please clarify the name of the attribute "previous" in Discrete time state Mar 19, 2020
@chrbertsch

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@chrbertsch chrbertsch commented Mar 20, 2020

Regular Design Meeting:

Klaus: There is an additional interpretation, that in case of an event it could be left limit.
If you just call it previous, it is ambiguous.
In Modelica, there is a pre(), meaning the left limit.

Claudio: There are different interpretations possible.

Klaus: you can have many iteration in event iterations. If you have 10 iteration, previous could be the ninth?
Klaus: Why do we need it at all? The master can track the variables.
Markus: Some for features in the working group were introduced by people who are no longer active in the working group.

Conclusion: We currently do not know what previous is needed for. We will remove it, if there is no rationale why we need it and a clarification is provided

@Modelicans and others: Please comment and contribute to the working group if you need this feature. @HansOlsson @TorstenBlochwitz, Rüdiger Franke, Fabio Cremona ...

@andreas-junghanns

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@andreas-junghanns andreas-junghanns commented Mar 27, 2020

web design meeting: We could not find any "previous" anywhere in the history of the github repository. We cannot easily find out how it was introduced, we agreed to drop the this attribute from the text.

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@andreas-junghanns andreas-junghanns commented Mar 27, 2020

Pierre will create a PR to remove this from the text. See also #738

pmai added a commit that referenced this issue Mar 27, 2020
Same as future perfect it was found not to be...
Fixes #853 and #738
pmai added a commit that referenced this issue Mar 27, 2020
Same as future perfect it was found not to be...
Fixes #853 and #738
pmai added a commit that referenced this issue Mar 27, 2020
Same as future perfect it was found not to be...
Fixes #853 and #738
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