A user with Viewer profile to open a model from Mart and try to switch to another subject area and got message: You do not have Modify permission on the model

Q: Using erwin Mart r9.7 with Viewer profile on a folder. User opens model and wants to switch to another subject area. This fails with "You do not have Modify permission on the model". We do not want to grant Modify on this folder. Why is Viewer profile not allowing user to change subject areas?

A: When switch subject area, the relationship in the model will be re-writing which consider a modify on a model and will show the message below:

"You do not have Modify permission the Model. Please contact the Mart Administrator for more permissions. 
To complete this operation, detach this model as a non-mart ;model. 
This is not an undoable operation. 
Do you still want to detach this model from the mart? 
Click 'Yes' to detach this model as a non-mar tmodel. 
Click 'No' to cancel this operation.

So by design,  a person with Viewer profile will always get this message when they try to change from one SA to another. The workaround is that they should  respond with "Yes" on the message above to provide a non-mart model that they may then freely navigate about in.