This information is part of the Modelica Standard Library maintained by the Modelica Association.
Error message, if variable is not assigned
connector Frame "Frame of a mechanical system" ... flow Modelica.SIunits.Force f annotation(unassignedMessage = "All Forces cannot be uniquely calculated. The reason could be that the mechanism contains a planar loop or that joints constrain the same motion. For planar loops, use in one revolute joint per loop the option PlanarCutJoint=true in the Advanced menu. "); end Frame;
annotation"(" unassignedMessage "=" STRING ")"
When the variable to which this annotation is attached in the declaration cannot be computed due to the structure of the equations, the string message can be used as a diagnostic message. When using BLT partitioning, this means if a variable "a" or one of its aliases "b = a", "b = -a", cannot be assigned, the message is displayed. This annotation is used to provide library specific error messages.