Collaboration in SocialCalc

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[edit] Collaboration in SocialCalc

1. Vijit Singh has prepared a detailed document on collaborating SocialCalc over the mesh network. Please find the document attached File:Collaboration SocialCalc on Sugar.pdf or see the guide here.

2. Audrey Tang is working on developing the multi-user editing, via visualizing peer's e-cells with colored borders. Please find her detailed notes and documentation on architecture and development as follows.

[edit] Notes by Audrey Tang

Update 2009-10-29: Gave a talk on the 4hr-long implementation session at YAPC::Tiny tonight; slides are up at - You may recognize two people's pictures in it. :-)


Update 2009-10-28: Peer cursor visualization and concurrent edits are both implemented at GitHub [1], using the Tatsumaki framework [2] from @miyagawa. Seems to work well enough for a prototype. :-)


Note also that at this stage this is a personal off-$work-time hack project; writings here are solely my personal opinion, not representative of commitments or decisions from the Socialtext team.

To enable collaborative editing in a general web setting, we're working with two different constraints compared to OLPC:

  • The transport has to be reasonably cross-browser. In decreasing order of preference:
    • Simple JS client over specialized server: nginx_http_push_module [3] looks good here.
    • Complex JS client realizable in multiple client implementations, over multiple server implementatinos: Bayeux [4] is the prime candidate here.
      • BOSH [5] is similar, but needs additional effort to tease apart the XMPP-specific bits.
    • Adobe Flash messaging [6], which works very well, but browser support (e.g. iPhone) is not yet universal.
  • There must be no accidental overwrites caused by multiple people entering into the same cell.
    • We can visualize other peer's current cell via locked backgrounds, avatar icons, etc.
    • Then, to solve it in a cheap-but-cheerful way, we can simply lock a peer-cell's focus.
    • To be less strict, we can also allow focus into peer cells, but disable all "set text" calls on them.

Happy hacking!