[pmwiki-users] Simultaneous Editing

[Peter Bowers]

On Mon, Apr 6, 2009 at 9:39 PM, Lane Lester <llester at info-fast.com> wrote:

> I have a classroom network of 8 computers, and to see what would happen, I
> had students at all 8 start editing the same page. Messages cropped up
> saying that if a page were saved, the work done by others would be lost. So
> we ended up taking turns at editing and saving. Is that just the way PmWiki
> works, or is there a way to let students edit the same page freely?
>

Re-reading your message perhaps it's simply a misunderstood warning
message.  If more than 1 person tries to edit a page at the same time there
is a cautionary warning that comes up on the edit page saying "your changes
will overwrite the changes made by someone else" or something like that.
While this is true technically (whoever saves last always wins) pmwiki does
a very nice job of merging the changes together before it saves (it prompts
you with the new version after it merges the changes).  In other words if
person A and person B open the file at the same time and A makes a change at
the top and saves and B makes a change at the bottom and saves, person B
will get a screen back with BOTH A's and B's changes and then will be
prompted to save that merged version.  If there are conflicting changes then
they are marked relatively clearly and the editor has to edit it manually to
resolve the conflict.

Now if you have 8 different students all editing the same page at the same
time and all saving at roughly the same time then you are almost certainly
going to get into a bit of a mess...  Pmwiki will handle locks such that
each update is done sequentially, merging changes appropriately and
prompting each sequential editor to save, so technically it will all be
good, but practically speaking you just can't have 8 different people
editing the same page at the same time unless you expect a pretty messed up
page and an awful lot of error messages and warnings...

Summary: Pmwiki does a very nice job of handling the occasional simultaneous
edit, but practically speaking the human dimension means that many
simultaneous edits are going to be a bit confusing to your students.

-Peter
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