[Standards] whiteboarding and shared editing

Mats Bengtsson matben at privat.utfors.se
Wed Aug 15 06:32:33 UTC 2007


Peter Saint-Andre:
> In its meeting on Wednesday, the XMPP Council declined [1] to accept the
> most recent SVG whiteboarding proposal [2] as a XEP. However, the
> Council appreciates the efforts of those who have worked on the
> technology underlying that specification, which may provide helpful
> experiential input to standards-track work in this domain.

When this was discussed extensively last summer I promised to write an Informational XEP,
which I so far have failed to do. Sorry for this.
As a temporary mean I have put it on a web page: http://coccinella.im/memo/sync
One word of caution: do not get annoyed about all the formal stuff since this
just presents proof which very few people need to care about.
The bottom line is that the method is very simple; each item just needs an extra
version attribute that need to match for each edit.
Now one year after I wrote it I don't understand a word of it :-(

Anyhow, if I remember correctly there are two basic assumptions in it that are
not always valid:
 1) each item is independent of any other item
 2) the initial states are identical

First, if an item is moved (stack level) in the document tree and another item is used
as a reference position, the first assumption is not valid anymore. But Joonas had a simple
mechanism for this, and it shouldn't be difficult to solve.

Second, in group chats where people come and go, the second assumption is not true.
This is much trickier to solve. As I remember Joonas and mine discussion, if the group chat
service kept a kind of virtual participant that recorded everything that happened, that
could be used to send its state to newcomers. There are likely more solutions to this
problem, but we couldn't come up with a simple one.

Mats




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