2009/387 [Pathname Reparse Points]

[Alan.M.Wright]

Ah, this is Aegis.  I used Aegis in the mid-80s (with Cadre Teamware).
I moved on to SunOS and hadn't realized it was renamed to Domain OS.

Thanks,

Alan

----- Original Message ----- 
Richard L. Hamilton <rlhamil at smart.net> wrote:
>> > Is this intended to be something like the
>> conditional symbolic links that have
>> > been in Apollo Domain system 23 years ago?
>> >
>>
>> I'm not familiar with that proposal.  Can you provide
>> details?
>>
>> Thanks,
>>
>> Alan
>
> As I recall, Apollo Domain OS implicitly made environment variables 
> available
> to "system calls" (the quotation marks being because the OS was different 
> enough
> that traditional system calls might often have been implemented more in user
> space than is typical on the historical Unix code-base).  Therefore, 
> symlinks
> on Domain OS could contain environment variable references; I think these 
> looked
> like $(name);  so they might have symlinks like
>
> /usr -> /$(SYSTYPE)/usr
>
> where SYSTYPE could be sys5.3 or bsd4.3.  (give or take details, I recall 
> that as an
> actual example)
>
> Of course, Apollo also did some other odd things with path names:
>
> //nodename
>
> referred to the / direcctory of node nodename, as seen by other nodes
> (similar to AFS /afs/node, or automounter /net/node)
>
> `node_data
>
> referred to the per-node private data directory (/sys/node_data on a diskful
> node, something like /sys/node_data.nodeid on the diskful partner of
> diskless node nodeid)
>
> And Apollo had a "typed" filesystem, where types for device files, symlinks, 
> FIFOs,
> Unix-domain sockets, and unstructured files were only _some_ of the types; 
> others
> could be for record-oriented files, windowing system entities (scrolling 
> back through
> a transcript pad with mixed text and graphics would replay the graphics! - a 
> "terminal"
> based on such a transcript pad was effectively seekable, but append-only for 
> writing),
> files that incorporated revision history (the ancestor of Rational Rose), 
> etc.
> In some cases, something that was not a directory could be other than the 
> last
> level of a path name, in which case it would be up to the object at that 
> level
> to interpret the "residue" of the pathname.
>
> (They also had a form of ACLs long before those were commonplace on other
> Unix-like OSs.)
>
> So while the Apollo was IMO a _brilliant_ example of what's possible, some 
> of what
> it could do exceeds what would readily fit the Unix model (although it could 
> present
> a very credible approximation of that model as a subset of what it could 
> do).  And
> thus, examples from an Apollo may be useful in terms of thinking about a 
> problem,
> but could often not be reasonably implemented to look similar on a more 
> traditional
> Unix-like OS.
>
> (way OT: ISTR one limitation on the Apollo: anything that was executable was
> effectively also readable, due to some architectural constraint)
> -- 
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