Google Cast was originally built on top of DIAL, but DIAL itself is mostly about device discovery IIRC. Nowadays it's all mDNS instead.

DIAL is literally discovery and launch. The discovery part is just SSDP. The rest of DIAL is entirely state tracking the stream, sending playback commands, requests to launch content, etc. through REST endpoints. It seems entirely possible to me for a revision of the spec based off mDNS for discovery rather than UPnP, and most of the document would be the same.

The DIAL spec documents spend three pages talking about discovery and sixteen pages talking about state tracking, launching, HDMI-CEC, etc.

It's a pretty basic protocol spec since it mostly relies on things like UPnP for discovery and HTTP REST so a lot of complications are already defined in other specs.