Definition of 'Queue_length' cannot access a hidden definition.
An expression is attempting to access the definition of a variable or user function that has a hidden definition. The ability to hide definitions is a feature of the Analytica Enterprise edition, with can be used to hide definitions containing proprietary algorithms or other content. If you were able to access that definition using an expression like
(Definition of Queue_length), it would defeat that feature.
If you really want to access the definition in this manner, then you will need to unhide the definition. You cannot do this if you are working with a locked copy of the model. Otherwise, select the variable (
Queue_length in the example) and then select Unhide Definition on the Object menu.
If this error occurs in an expression that traverses many objects, and you want to continue in these cases, then you should ignore warnings,e.g.
IgnoreWarnings(Definition of Queue_length)