Revisions are a means to save a specific state of a document, e.g. as an interim result of a digital edition. New Revisions are explicitly created by the user, and all Revisions of the same base Object are in the same Project. TextGrid uses an mechanism to lock an Object if a user is working with it. A second user will receive a message when opening the same Object if the first user is still working on it. He or she has then only the right to read but not to change the document.