What happens if a user doesn't have an add-on?

Hi, I’m thinking of trying an add-on / drop-in for Eclipse Capella. I’m working asynchronously (locally) and then re-uploading to shared file storage.

If I add ‘Requirements Viewpoint’ and add a bunch of requirements objects to diagrams, then what happens if another user (without the add-on) downloads this .capella and .aird files and tries to view it on their local machine; what will they see? Will the model open? Will it result in an error?

This will result in an error unless they install the same add-on as you.

Note that if you need to send the model to someone who cannot get the add-on (maybe its a company developed non-open source add-on), it is possible to detach the viewpoint and return it to a state that they can view… but this will mean the data is lost for them.