MSC3672: Sharing ephemeral streams of location data

[stefanceriu]

In which we build on top of MSC3489: Sharing streams of location data and MSC2477: User-defined ephemeral events to share streams of location data in a non-persistent way.

Rendered

Shepherd: @anoadragon453

[deepbluev7]

I think this needs a bit of a longer justification of why this is needed and why EDUs are the way to go. Some ideas:

• EDUs are not persisted in the timeline -> A user can only access the ones they received originally.
• EDUs can be stored indefinitely on the server, but because they are E2EE, this should not cause issues.
• What are the semantics for the last EDU? When do they expire? Do you always get the last sent one on initial sync? Does a client need to clobber that with a dummy?

[stefanceriu]

Thank you. I've added more details for the first two points but perhaps the last one should be taken up in MSC2477?
I don't think there should be any special behavior for location sharing.

[deepbluev7]

It might make sense to pick that up in the justification for a bit, i.e. "You can make EDUs expire after some time, so they never get delivered to devices, which are offline for some time" or so, if that is actually possible with 2477. It's been a while since I read it.

[andybalaam]

I added some wording about how long the server should keep the EDUs, and I think the beginning part of the Proposal section clarify the justification for EDUs. What do you think @deepbluev7 ?

[deepbluev7]

Took me a while to find, but yes, that looks reasonable. Does that work when the EDU is encrypted? Because then the event type is m.room.encrypted, isn't it?

[andybalaam]

Sorry, I should have provided a proper link.

I expect that if we later add the ability to specify delivery guarantees for EDUs, we will include that in the unencrypted part. Before we have that, servers will have to apply the same policy to all user-defined encrypted EDUs.

[anoadragon453]

Heads up that @stefanceriu has moved on to other work. In their place I'll be acting as a shepherd and will be updating this MSC as new feedback comes in.