[QUESTION] Using multiple dictionaries for a singular resource

[TheArcaneBrony]

I'm not sure if this would make any sense, but could it be possible to support using multiple dictionaries for a single resource?

Concrete example: Say I run an online communication service (ie. a chat service) - It might make sense for me to use a shared (& likely static) dictionary for protocol layer compression, but it might also make sense to use a separate dictionary - which would be gated by access controls - to have a dictionary of very frequently re-occuring data, such as user IDs of members of a private channel, the first few digits of a timestamp, etc

[martinthomson]

I'm guessing that this is about compression dictionaries.

I'm also quite sure that this is too late to change in the way you describe. Work on an alternative or extension is possible if you can demonstrate value, but I suspect that the bar is pretty high.

[pmeenan]

It was an intentional design decision to only allow for a single dictionary to be available at a given point in time and for the client to pick the "best" from the ones it has available for a given request at the time the request is made (for a bunch of reasons, but the biggest is to minimize the cache key explosion for server-side caches that can come from vary: available-dictionary.

What you're describing, if I understand it correctly, could be handled by having the "separate dictionary" include the protocol-layer patterns as well as the data patterns and use the basic dictionary to compress the more-advanced (and specific) one. The advanced one could be scoped to individual channels/whatever based on URL pattern matching so you could have different advanced dictionaries for different channels.