The model comparison can be performed with the versioning states Current version and Change list number.
If the current version is compared to a different version selected using the change list number, the selected models are locked to prevent editing. If, on the other hand, a version, version is compared to the workspace model, the latter can be edited as normal. If you edit the model and then close the model comparison, you are asked whether you want to save your changes, if you have not already done so.
Versioned models can be identified by the fact that their names are followed by a version number displayed in parentheses. The names and version numbers of the models are used collectively as the title of the tab and are displayed individually above each model.