I can imagine dictionaries as being useful for: 1. Pre distributed dictionaries for commonly transmitted data types. Ie: web browsers could ship with a shared

I can imagine dictionaries as being useful for: 1. Pre distributed dictionaries for commonly transmitted data types. Ie: web browsers could ship with a shared dictionary that is generally helpful for JavaScript, then servers could negotiate and send a specially compressed version for those that have the dictionary. 2. Streaming buffered data: eg before sending video, send a dictionary. This is useful because we are interested in compressing each chunk well, not just the overall file. Relatedly - a compression scheme where you need all bytes before you can decompress any is rather useless here.