We've already discussed this in other contexts. This is what I meant when I
talked about "levels of meta" and why invoking a function is more benign than
using a global assignment (which is tantamount to redefining a function under
program control), etc.
And certainly to allow unprotected "rewiring" under program control without
"possible worlds reasoning" makes a very fragile system indeed (and so many of
them out there are).
Generally speaking, the amount and depth of required design increases greatly
as one traverses into meta. (And just who should be doing the designs at each
level will (should) become a narrower more expert group.)
One of the interesting metafences that has been discussed in STEPS (and it
would be great to move from talk to some examples) is the enforced separation
of meaning from optimization. If they are in different worlds (where any and
all of the optimizations could be turned off and the system would still run)
then this "sideways" augmentation can be hugely useful and still very safe.
The MOP example in the book could be considered to be one of these, but the
book omitted this set of ideas. Still, you could imagine setting things up so
that the new variant would be automatically checked by running the meaning in
parallel, and this would make everything much less fragile.
I think there is real gold here if these sets of domains and "fences" could be
worked out.
Cheers,
Alan
>________________________________
>From: Casey Ransberger <casey.obrie...@gmail.com>
>To: Fundamentals of New Computing <fonc@vpri.org>
>Sent: Wednesday, September 7, 2011 12:48 PM
>Subject: [fonc] Tension between meta-object protocol and encapsulation
>
>
>This has been bugging me for awhile. This seems like the best forum to ask
>about it.
>
>
>"With great power comes great responsibility." This quotation is hard to pin
>down. There are several versions of it to be found. This particular phrasing
>of the statement probably belongs to Stan Lee, but I think the phrase, in
>another form, is older than that.
>
>
>It seems to me that there is tension here, forces pulling in orthogonal
>directions. In systems which include a MOP, it seems as though encapsulation
>is sort of hosed at will. Certainly I'm not arguing against the MOP, it's one
>of the most powerful ideas in programming. For some things, it seems
>absolutely necessary, but then... there's the abuse of the MOP.
>
>
>I've done it to spectacular effect :D and when one is under constant pressure
>to ship, one tends to reach for the longest lever in the room.
>
>
>On one hand, I can avoid writing a lot of code at times this way, but on the
>other hand, what I've done is liable to confuse the hell out of whatever poor
>bastard is maintaining my code now.
>
>
>I've also had to wade through some very confusing code that also did it. You
>know, as long as it's me doing it, it's fine, but there's only one of me, and
>there's in the neighborhood of 6,775,235,700 of you!
>
>
>Is this tension irreconcilable?
>
>
>--
>Casey Ransberger
>
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>
>
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