Two remarks about Plan 9, one about an antecedent and the other about the
limits of its influence.
"Communication files" in the Dartmouth Time Sharing System have been cited
as a predecesssor of Unix pipes, although we at Bell Labs were unaware of
the DTSS feature when pipes were first implemented. In fact, communication
files more directly foreshadow Plan 9 than they do Unix.
Unlike Unix processes, which need not be aware that they are talking to
pipes, the process at one end of a communication file, designated as
"master", must be aware that it is a communication file. The master end
controls the semantics of reads, writes and seeks(!) issued at the other
end. Because of this asymmetry, a communication file cannnot serve as a
pipe between pairs of unprepared processes. A pipe could be simulated in
DTSS by a master process that relays flow between communications files
connected to arbitrary end processes, but that seems never to have been
done.
Communication files are a closer antecedent to Plan 9. A master process's
controls correspond to the part of Plan 9's foundational 9P protocol that
handles open files. Though I don't think there's an actual ancestral
connection, this likeness strengthens DTSS's claim to fame and extends
their lead to nearly a quarter century.
Linux has adopted surface features of Plan 9 like union directories,
append-only files and system data access via file interfaces. Meanwhile
Plan 9's revolutionary realization of what Vic Vyssotsky called
distributable computing has not caught on. In distributable computing, the
physical location of processes does not affect their logical interaction.
In today's distributed computing, though, there is a world of difference
between how processes interact remotely and locally. When will the crevasse
between the possible and the normal be bridged?
Doug
Having recently read about the playful literary consortium, Oulipo, I am
reminded of their term for little-known antecedents of their revolutionary
works: "anticipatory plagiarism".
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