[rucksack-devel] Re: Rucksack, ECLM

[Nikodemus Siivola]

"Arthur Lemmens" <alemmens at xs4all.nl> writes:

>>  Rucksacks A and B open.
>>  Persistent Class FOO is defined.
>>  Instances of FOO are stored in Rucksack A.
>>  Other instances of FOO are stored in Rucksack B.
>>  Rucksack A closes.
>>  FOO is redefined, schema in B updates.
>>  Rucksack B closes.
>>  Lisp exists.
>>
>>  New lisp sesssion.
>>
>>  Rucksack A is opened and instances of FOO are fetched.
>>  Rucksack B is opened and instances of FOO are fetched.

> I think the basic guideline should be that rucksacks never need to know
> about each other.  And another assumption is that the most recent class
> definition comes from your program source, not from a rucksack.  The
> schemas in a rucksack are just a way to make sure that Rucksack can adapt
> old instances to the current class definition in your program.

Right. What it there is no definition for class FOO in the new session?
A LOAD-YOUR-STUFF-RIGHT-NOW-ERROR is signalled, I assume.

> So when a rucksack is opened and fetches an instance of FOO for the first
> time, Rucksack should probably do the same thing as when a class is
> redefined: compare the current class definition with the most recent

Makes sense.

> Does that sound reasonable, or am I missing something?

I can't think of anything offhand. ;-)

The only point remaining is objects whose Rucksack has been closed: I
assume they are effectively dead, and touching them isn't allowed?

> I hope I've shown that this prohibition is not necessary.

Yes. 

I'll do a short writeup on the desired semantics (based on this
discussion) -- both so that I have chance to think this through again,
and so that we can see if what I have understood is what you have
ment.

Cheers,

  -- Nikodemus              Schemer: "Buddha is small, clean, and serious."
                   Lispnik: "Buddha is big, has hairy armpits, and laughs."