This question "Egyption Fractions in C" was originally posted with the following tags:

The question was obviously not about , so I took advantage of my >12K reputation to remove it via the "edit tags" link.

A few hours later I come back and Ashot Martirosyan posted a comment about why I have removed the tag. Confused, I went back to the edit history of the question and indeed it showed that I removed the tag. Now, I'm not a math professor but I'm not math illiterate. I can tell that the question had something to do with math.

It shows that I've submitted the edit at 2011-03-20 05:55:15Z. Ashot Martirosyan submitted this edit at 2011-03-20 05:55:14Z:

Clearly I didn't see that the tags were fixed before I've submitted my tag edit since my edit and Ashot Martirosyan's were one second apart. I'm sure the total time for me to read the question, read the tags, make the proper mouse movements and keystrokes then submitting the edits takes much longer than one second.

Apparently the tag editing system used some kind of position-based indexing system since and occupied the same position relative to and , so instead of removing it removed Ashot Martirosyan's edit instead.

Now, I realize that concurrent editing is going to happen on a site as popular as Stack Overflow. But is it possible to make the engine powering Stack Overflow figure out that my edits were based on outdated previous edits? I realize that I get notified for concurrent post edits asynchronously, but I was hoping it could work like version control where I get notified of conflicts if I attempt to push my changes.

2 Answers 2


It's simply a race condition in the edits.

Both of your edits started with .

He replaced with , so the tags in his revision are .

In the mean time, you removed from the original tag set, so your revision has the tags .

Since you saved later, the edit history shows that between his and your revision the tag disappeared, since your changes overwrote his changes. The version that is saved last always wins, it doesn't matter what the "base revision" of that edit was.

Like with any other edit conflicts there is no notification that your "Save Edit" just overwrote some other edit that you might not have seen yet.

  • 1
    I figured this was the case. It would be nice to know I overwrote changes I haven't seen yet so I can fix it at that moment and not hours later. But thanks for your response.
    – In silico
    Mar 21, 2011 at 2:04

This is by design for now, but you may want to vote up any of the "better handling of edit conflicts" suggestions.

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