No, I don't quite agree. All compressors have a model, at least the general purpose ones. If you're writing self-extracting compression for your 8-bit demo, may

No, I don't quite agree. All compressors have a model, at least the general purpose ones. If you're writing self-extracting compression for your 8-bit demo, maybe you only care about the data you have right in front of you... But for anything general purpose, from DEFLATE to paq, there's an implicit, fixed model of future data in there (even if we sometimes prefer to see it as an "adaptive" model). A good illustration of this is that you can quite easily use a general purpose compression algorithm for classification, and get surprisingly good performance.