title: Change annotation(Evaluate=true/false ) for parameters in models from Modelica Standard Library
body: <p>I am using some components from the Modelica Standard Library (MSL) in my simulations. These components each have some parameters. For example, <code>Modelica.Fluid.Sources.MassFlowSource_T</code>  has a <code>parameter m_flow</code>. Usually, parameters can be changed between simulation runs without re-compilation. This is not the case for <code>m_flow</code>, because it has an <code>annotation(Evaluate=true)</code>, so it is used for symbolic processing.<br>
  Is it possible to change the annotations of parameters at instantiation? I tried the following, but it didn't work. </p>
  
  <pre><code>Modelica.Fluid.Sources.MassFlowSource_T source2(
      redeclare package Medium = Medium2,
      nPorts=1,
      m_flow=22.17 annotation(Evaluate=false));
  </code></pre>
  
  <p>Of course there are workarounds, like making a copy first and changing the annotation there or using <code>use_m_flow_in=true</code> and a constant source block.</p>