The Story Begins …

Alice and Bob have both pressed Edit This Page on the same page and so they both have the same page open for editing.

Alice finishes her edits first and presses the Save button. The official page now includes her edits.

Bob doesn’t know this and continues with his edits which are based on a stale version of the page — one without Alice’s new edits. But Bob doesn’t know the the page which he started to edit has now be superseded.

Bob finishes his edits and presses the Save button, expecting the official page to now to be updated to be like he had just edited it to be.

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What happens next?

Version 1

[This is current behaviour on 2013-08-19 Mon, but is listed on Bolzano_Known_Bugs as something which needs to be fixed.]

The official page with Alice’s edits is completely overwritten with Bob’s version of the page, with no traces of Alice’s edits.

Bob is completely unaware that someone else’s edits have been silently discarded. Being a collaborative person, he would not have wanted this if he knew. In fact, had he known of Alice’s edits, his own edits would have been different.

Alice, who left after completing her edits, is completely unaware that her edits have been discarded. When she next visits the page she will see no trace of them. She might see some of Bob’s edits and think that Bob had deleted all her edits. But Bob never saw them, though he would have liked them if he had.

When he finds out, it makes Bob a sad panda](http://www.urbandictionary.com/define.php?term=sad%20panda)) http://i.imgur.com/TKs8BZK.jpg

This is not regarded as a Good Thing](http://www.retrologic.com/jargon/G/Good-Thing.html))

Version 2

Bob is presented with - A short message explaining that someone has edited the page since he last looked at it. - The new page, as edited by Alice, in edit mode. He can now edit the up-to-date page. - A separate text area below with the source of his own edits as he most recently left them. This is for him to copy-and-paste from as he edits the up-to-date page.

Bob edits the up-to-date page in light of Alice’s recent edits, possibly copying some of his previously typed stuff from the window below to the relevant part of the page.

Version 3

• Bob is presented with short message explaining that someone has edited the page since he last looked at it.
• His edits are not included in the official page.
• He knows he can read the up-to-date page then edit the page based on that.
• There is a Page History available where Bob can get some of the material he previously typed if he needs to.

Version 4

Some sort of automatic merge, which probably should be attended to by a human anyway, and in some cases would need to be or else the page would be in a messy condition.

Ideally the person who edited second should sort it out. But if they don’t notice where all the “diffs” are, or if they just walk away without looking, the page is left un-reviewed. So it might be best to not do the automatic merge. If the second editor still wants to add content they’ve got to do it consciously, using their human judgement.