Re: Intended meaning

From: FRANCISCO JAVIER LOPEZ FRAGUAS <fraguas_at_sip.ucm.es>
Date: Wed, 07 Nov 2007 09:16:32 +0100

> if this smaller subset can be extended in a simple way such that one

> regains the advantages of free variables (like generality of

> solutions)



However, if the simpler setting is extended by some

ad-hoc treatment of generators, the result could be not simpler anymore!

All this is of course arguable, and in my opinion both the narrowing approach

 to free variables and the generator approach merit further research.

It is good  to have both at hand.



> Yes and know, depending on what semantics you think. From a

> denotationalpoint of you I fully agree with your statement.

> Again this is the

> advantage to have well studied concepts. But for the strategic,

> operational point of view it makes much sense to treat (?) specially.



We coincide then at this point, since this was also my opinion.



However, I'm not sure to understand your comment:



> When thinking about that it is a great

> help to

> know that (?) combines independent computations. And any sharing

> across(?) essentially says that the computations may not be so

> independentafter all.

>



Is it  related to the property that C[e ? e'] should be equivalent to C[e] ? C[e'],

for any context C and expressions e, e' ?

 I remark that the property is certainly true

for CRWL programs. An interesting point is that the

proof of it is easy if one uses semantic-based reasonings.

Thus, an operational procedure can use the above equivalence

while preserving the semantics.

Has this any relation to your comment?



Best,



Paco







----- Mensaje original -----

De: Bernd Brassel <bbr_at_informatik.uni-kiel.de>

Fecha: Martes, Noviembre 6, 2007 5:53 pm

Asunto: Re: [curry] Intended meaning

A: "Francisco J. Lopez Fraguas" <fraguas_at_sip.ucm.es>, curry_at_lists.RWTH-Aachen.DE



> Francisco J. Lopez Fraguas schrieb:

>

> > In any case, the use of generators/rewriting to replace free

> variables/narrowing> does not need any new theory nor formal

> setting (this doesn't mean that

> > nothing interesting can be investigated).

> > Existing formalisms (CRWL and its

> > rewriting-with-let-bindings counterpart --see our ppdp07--, or

> the operational

> > semantics of JSC mentioned by Michael) cope perfectly with

> generators,> which conceptually are not different from any other

> function, as happens

> > also with the function ?.

>

> Yes, I fully agree. And that is the merit of such an approach

> that you

> do not need any new concepts but rather a smaller subset of the

> originalconcepts. And what is interesting to investigate (as you

> also stated) is

> if this smaller subset can be extended in a simple way such that one

> regains the advantages of free variables (like generality of

> solutions)

> > I don't think that giving to generators or to ? a special

> > status from the point of view of the semantics (intended or

> formal) is a real

> > need,

> > not even an advantage.

>

> Yes and know, depending on what semantics you think. From a

> denotationalpoint of you I fully agree with your statement.

> Again this is the

> advantage to have well studied concepts. But for the strategic,

> operational point of view it makes much sense to treat (?) specially.

> Remember that Sergio said that he is looking into possibilities for

> parallelizing strategies. When thinking about that it is a great

> help to

> know that (?) combines independent computations. And any sharing

> across(?) essentially says that the computations may not be so

> independentafter all.

>

> > A different question is the interest of developing an

> operational procedure

> > where computations produce set of values, instead of

> individual ones.

> >

> > This is interesting in many aspects, has been addressed

> several times,

> > and might profit of a sage usage of generators combined with

> ?, as it seems

> > you are working out in your recent papers.

> > But I don't think that this needs changing the foundations of FLP.

> > Instead, in my opinion such collecting procedures should guarantee

> > equivalence with the semantics given to individual

> computations in previous

> > proposals (CRWL, JSC, ppdp07).

> > This was done for instance, for CRWL and the set-valued

> semantics in our

> > lpar01/flops02 papers.

>

>

> But even if such an approach to "collecting procedures" guarantees

> equivalence with the semantics for independent computations, it

> is still

>  a substantial extension of he foundations of FLP, or don't

> you think?

> And I have the intuition (maybe with Sergio ?) that studying the

> sharingstructure and having the strategy give special treatment

> to (/) might be

> a key issue for that.

>

> Greetings

> Bernd

>

********************************
Francisco J. Lopez Fraguas
Dep. Sistemas Informaticos y Computacion
Fac. Informatica U. Complutense Madrid
Prof. Jose Garcia Santesmases s/n
28040 Madrid
Spain

fraguas_at_sip.ucm.es
Tel: +34 91 3947630
Fax: +34 91 3947529
********************************




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Received on Wed Nov 07 2007 - 09:28:37 CET

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