id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
6259	Free parameters mess up FMI model structure	Rüdiger Franke	Karim Adbdelhak	"See the following example:
{{{#!mo
model SI1 ""Single Integrator with fixed parameter""
  parameter Real p = 1 ""gain for input"";
  input Real u(start = -2);
  output Real y(start = p);
equation
  der(y) = p * u;
end SI1;
}}}
for which FMI 2.0 export generates the following reasonable Outputs and Derivatives structure in modelDescription.xml. InitialUnknowns appears a bit ""over-engineered"" (y alias, der(y) and y unknown; der(y) depending on u and p):
{{{#!xml
  <ModelStructure>
    <Outputs>
      <Unknown index=""4"" dependencies=""1"" dependenciesKind=""dependent"" />
    </Outputs>
    <Derivatives>
      <Unknown index=""2"" dependencies=""3"" dependenciesKind=""dependent"" />
    </Derivatives>
    <InitialUnknowns>
      <Unknown index=""1"" dependencies="""" dependenciesKind="""" />
      <Unknown index=""2"" dependencies=""3 5"" dependenciesKind=""dependent dependent"" />
      <Unknown index=""4"" dependencies="""" dependenciesKind="""" />
    </InitialUnknowns>
  </ModelStructure>
}}}

Now see a model with slight modification (free parameter):
{{{#!mo
model SI2 ""Single Integrator with free parameter""
  parameter Real p(fixed = false) ""gain for input"";
  input Real u(start = -2);
  output Real y(start = p);
initial equation
  p = 1;
equation
  der(y) = p * u;
end SI2;
}}}
Outputs and Derivatives loose their dependencies. The now more interesting InitialUnknowns disappear completely:
{{{#!xml
  <ModelStructure>
    <Outputs>
      <Unknown index=""4"" dependencies="""" dependenciesKind="""" />
    </Outputs>
    <Derivatives>
      <Unknown index=""2"" dependencies="""" dependenciesKind="""" />
    </Derivatives>
  </ModelStructure>
}}}
What happens to dependencies of Outputs and Derivatives?"	defect	new	high		Backend	v1.17.0-dev