Execution of multiple event assignments from the same event

[dweindl]

Multiple event assignments from the same event should be executed simultaneously. From the SBML L3V2 specs:

In other words, a single event cannot have multiple EventAssignment children
assigning the same variable. (All of them would be performed at the same time, when that particular
Event triggers, resulting in indeterminacy.)

However, that doesn't seem to be the case:

AMICI/python/sdist/amici/sbml_import.py

Lines 1670 to 1673 in da19a55

	# else the species was affected by an event assignment,
	# hence the updated value should be updated further.
	else:
	species_value = bolus[state_vector.index(species_sym)]

I'd say, in the else case, that assignment should be ignored.

Example: Assuming a model with a concentration-based species S in compartment C, and an event with two event assignments – EA_S assigning to S and EA_C assigning to C.
In this case, S should only change due to EA_S, but not due to the volume change caused by EA_C. Currently, first EA_S is applied, then EA_C.

Correct?

[FFroehlich]

AMICI/python/sdist/amici/sbml_import.py

Lines 1670 to 1673 in da19a55

	# else the species was affected by an event assignment,
	# hence the updated value should be updated further.
	else:
	species_value = bolus[state_vector.index(species_sym)]

I'd say, in the else case, that assignment should be ignored.

Example: Assuming a model with a concentration-based species S in compartment C, and an event with two event assignments – EA_S assigning to S and EA_C assigning to C. In this case, S should only change due to EA_S, but not due to the volume change caused by EA_C. Currently, first EA_S is applied, then EA_C.

Correct?

Yes, sounds correct.

[dweindl]

Might have been correct before. I don't quite understand why, yet. But changing that leads to failures in:

• https://github.com/sbmlteam/sbml-test-suite/blob/release/cases/semantic/01779/01779-model.m
• https://github.com/sbmlteam/sbml-test-suite/blob/release/cases/semantic/01780/01780-model.m
• https://github.com/sbmlteam/sbml-test-suite/blob/release/cases/semantic/01506/01506-model.m

[dweindl]

From elsewhere in the SBML spec (sec 4.6.8):

There is one exception: if
the species’ quantity is determined by an AssignmentRule, RateRule, AlgebraicRule, or an EventAssignment
and the species has the attribute value hasOnlySubstanceUnits=“false”, it means that the concentration
is assigned by the rule or event; in that case, the amount must be calculated when the compartment size
changes.

It's not exactly intuitive and quite possibly a common source of error, but the present implementation is correct.