Re: Dynamic binding

[Joachim Parrow <joachim@xxxxxxxxx>]

Luca, could you enlighten me about what you mean by the difference between
"dynamic binding" and "dynamic scoping"? I am not sure there is a consistent
use of this terminology in the literature.

Certainly, your Ambients use dynamic binding, and as such have been a
significant inspiration for our work. Though I am not sure what you mean
when you say that this is a "perfectly normal lexically scoped calculus" -
to me lexical scoping means static binding, ie, something that satisfies
alpha-convertibility.

My feeling is that "dynamic binding" and "static binding" are two
fundamental and orthogonal mechanisms, and that both are needed in any
complex system. You can to some extent, as Michael says, encode dynamic
binding by communicating lambda-closures, but this scheme is not
satisfactory in open systems where the complete interfaces are not known at
compile-time. Or you can emulate dynamic binding by explicit symbol table
manipulations, but that is not a very abstract way to look at it.

Joachim

Luca Cardelli wrote:

> Before anybody rushes to revive dynamic scoping, I would like to point
> out that there is a difference between dynamic scoping and dynamic
> binding. The Ambient Calculus formalized dynamic binding (in the sense
> of, e.g., dynamically linking and unlinking program modules or
> agents/servers) within a perfectly normal lexically scoped calculus.
>
> You are absolutely right, though, that dynamic binding is of fundamental
> importance, and that there is virtually no programming language that
> supports it with specific constructs.
>
>         Luca
>
> -----Original Message-----
> From: Joachim Parrow [mailto:joachim@xxxxxxxxx]
> Sent: Thursday, March 01, 2001 14:43
> To: Joachim Parrow; mobile calculi mailinglist
> Subject: Dynamic binding
>
> Dear Mocanese,
>
> I would like to introduce a discussion topic: the issue of dynamic
> binding in mobile calculi.
>
> I don't propose to reopen all philosophical old arguments about dynamic
> binding, but there are some quite focussed technical questions involved.
> In mobile code dynamic binding is a reality, in associated higher-order
> formalisms like HO-pi it is most often absent. Now, supposing that the
> dynamic binding should be formally modelled, what is the best way to do
> it? Would you encode it or use some new primitve for it, if so how and
> what?
>
> My reson for introducing this at this time is that my student Jose Vivas
> recently finished his PhD thesis on dynamic binding in mobile calculi.
> Personally I have always been a hardliner in favour of static binding
> but Jose has managed to convince me to be more open-minded. But dynamic
> binding seems still very little discussed among theoreticians, so it
> would be interesting to hear what you all think.
>
> Jose's thesis can be found at
>
> http://www.it.kth.se/~josev/thesis.html
>
> Joachim Parrow

  
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