Hi, > node a is initially at state a0 > - user X create_changeset 1 > - user X change node a to state a1
> - user Y create_changeset 2 > - user Y change node a to state a2 > - user Y close_changeset 2 > - user X change node a to state a3 > - user X close_changeset 1 > > Now revert changeset 2. Changeset 2 cannot be reverted cleanly because the node is in state a3 but would have to be in state a2 in order for changeset 2 to be reverted cleanly. The user would possibly get a message informing him of the fact, and either asking him to somehow get the node into state a2 OR make a dirty revert. This is completely independent of whether or not the later change a2- >a3 happens in a changeset that was begun earlier than Y's. If changeset 2 were to be reverted dirty, the node would of course revert to a1 since that was the state the node was in before the operation. Changesets only group changes, they do *not* replace the existing version numbering of objects! If you think about how we handle things now: We have a timestamp on every object, but the "current" object is always the one with the highest sequence number, not the one with the most recent timestamp. I am suggesting to move the timestamp into the change group - as it is only informational anyway - but the sequence number remains the decisive element in determin which version of a node is current. The only thing slightly quirky about your example is that a node is changed twice as part of the same changeset. That doesn't make sense to me but maybe I'm too JOSM-minded; in a live editing scenario with Potlatch this might well happen. > To what state should node a revert? a0, a1, or a3? > And this is even a 'simple' case. But imagine much more complex > scenarios > where user Y is actually changing a turn restriction while user > X is changing the direction of one of the ways that is part of said > turn restriction. -- Frederik Ramm ## eMail [EMAIL PROTECTED] ## N49°00.09' E008°23.33' _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/dev
