On Thu, 21 Apr 2005, Daniel Hagerty wrote:
> > So magic is saying:
> > - The map is not the territory
> > - Here, use my map and see if that helps
> >
> > ?
>
> That could be magic. What you just said could read to me as
> "there is an abstraction underlying my concrete; apply this
> abstraction to your concrete and see if it helps" or similar (perhaps
> that isn't what I said originally, but it's certainly a useful
> expression here). There will no doubt be other things in the world
> that I would consign to "magic" if I wasn't careful.
Ok. To summarise, "magic" is the above plus other,
yet-to-be-defined stuff :). Yes? No?
> > So the oracle includes the items below:
> > - Language X (for want of a better term) which is standard, and
> > specifies the config you want
> > - The implementation of Language X which takes language X and makes
> > it happen on hardware a, b, and c
> > - Our own configuration in language X
> >
> > Yes?
>
> Took several attempts to parse, but if I see what you meant, yes.
>
> I can't be sure, due to the nature of communication. In
> particular, when we get to the point of needing precision, we need to
> examine key words like "language" and "configuration" to give them
> "proper" definitions. "Configuration" is *definitely* a problem word.
By language, I mean a programming or configuration language (poor
definition) eg. cfengine or perl.
By configuration, I mean a "program" written in the above
language. Although in a networks context, program usually specifies
desired state rather than a series of actions (sorry, proceduralist here
:) ).
[Bits snipped; I think I got them]
> Now, I'm going to hit the fast forward button a bit here; this
> will look a little blurry if only because I'm making this stuff up as
> opposed to having been taught it.
>
>
> Denotational semantic approaches boil down to producing some function
> such that
>
> denoted = f(sense)
>
> where "sense" could perhaps be a scheme program like "(set! foo 25)",
> or a perl program, or what have you. Magic is in figuring out the
> function f (and thus, denoted) for your language (scheme was intended
> to be "easy". Don't try to figure out f for perl.)
Ok, so I guess my "Language X" above is equivalent to a
definition of f(), my "implementation" above is an implementation of f(),
and my "configuration" above is equivalent to "sense". I'm glad to hear
my configuration makes sense :-} (<-- evil grin).
> Part of what is implied by the form above is that it is possible for
> the semantic to have a platonic, context free meaning. In the real
> world, it almost never works like that. I can run the "evil scheme
> program" that asks about the time, and depending on where I run it,
> different things will happen. If I send it out in mail to you as I
> have, that's one thing to the world's state; if I direct its output to
> /dev/null, that's another.
>
> "Configuration" is pretty much by definition dealing with questions of
> the form
>
> denoted = f(sense, context)
>
> where the concept of context becomes increasingly complicated. I
> could say more on the subject of context, but that would be getting
> ahead of myself.
>
> To justify the previous, consider the perl program:
>
> while($ARGV[0]){}
>
> This obviously is a "complete" perl program. However, its termination
> behavior is dependant upon "configuration"; there is state drawn from
> the broader world that affects what happens. Most any kind of
> interesting question we're likely to deal with is more likely to be
> specified in this form of a context, rather than the other form where
> the program is complete.
>
> As we're talking about producing languages (in this list, we're
> talking about "Network Management Systems" that can, for example
> "rollback") with well defined semantics, you should be noting the
> mathematical flames licking at the tension between trying to say
>
> denoted = f(sense)
>
> to our established mathematical tools, but asking questions of the
> form
>
> denoted = f(sense, context)
>
> in a fairly general fashion within the smaller expression.
Ok, I'm missing these last two bits. What are our "established
mathematical tools"? Are they currently existing languages like Cisco's
IOS config language?
:)
--
Tim Nelson
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