  Session types denote message protocols between concurrent processes, allowing
a type-safe formalization of inter-process communication. Although previous
works demonstrate a well-defined notion of subtyping where processes have
different perceptions of the protocol, these formulations were limited to
linear session types where each channel of communication has a unique provider
and client. In our work, we extend these previous formulations into the shared
session type setting where channels can now have multiple clients instead of a
single client. We demonstrate that this allows shared sessions to be released
at a different type, allowing the encoding of phases in a shared protocol to be
manifest in the session type.
