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A located lambda calculus

A located lambda calculus. Ezra Cooper and Philip Wadler. Submitted to ICFP 2008.

Several recent language designs have offered a unified language for programming a distributed system; we call these "location-aware" languages. These languages provide constructs that allow the programmer to control the location (the choice of host, for example) where a piece of code should run, which can be useful for security or performance reasons. On the other hand, a central mantra of web engineering insists that web servers should be "stateless": that no "session state" should be maintained on behalf of individual clients---that is, no state that pertains to the particular point of the interaction at which a client program resides. Thus far, most implementations of unified location-aware languages have ignored this precept, usually keeping a process for each client running on the server, or otherwise storing state information in memory. We show how to implement a location-aware language on top of the stateless-server model.

This paper is technical, and I assume most LtU members will mainly read sections 1, 5 & 6. Figure 5 is definition of the located LC.

By Ehud Lamm at 2008-05-04 19:25 | Lambda Calculus | Parallel/Distributed | other blogs | 10381 reads

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Defunctionalisation

Do you have some links that explain defunctionalisation and how it is useful in a client-server programming setting?

If the explanation is more informal all the better ;-)

By Denis Bredelet -jido at Sun, 2008-05-04 23:41 | login or register to post comments

Defunctionalization at Work

Defunctionalization at Work Also check the citations and citations of it.

Basically, defunctionalization is one of a few approaches to turn higher-order data into first-order data. If we CPS transform and then defunctionalize, we get a concrete representation of the (control) stack. I haven't read the paper of this topic yet, but I suspect that the purpose of defunctionalization and CPS transforming here is to reify control and easily store and serialize (and thus distribute) it.

By Derek Elkins at Mon, 2008-05-05 00:03 | login or register to post comments

Lambda into values

Nice, thanks for the link. So if I understood right defunctionalisation transforms a lambda expression into a series of values: the function label (or constructor, used for discrimination) and the free variables. A common 'apply' function returns the appropriate result when it receives an expression built with a specific constructor.

I understand what you mean by "reify control and easily store and serialize it". That way lambda expressions can be used in client-server communication, provided the recipient holds the code corresponding to the constructor sent over the wire.

By Denis Bredelet -jido at Mon, 2008-05-05 00:28 | login or register to post comments

Well-timed - one of the two

Well-timed - one of the two big drawbacks I've been thinking about recently wrt continuation based servers was the lack of mobility/serialization of continuations, which does not jive well with the ajax / thick client world. Some of the PLT Server papers mentioned work in progress in this area, but I don't recall anything beyond the paper on enabling continuations on top of traditional stack architectures (concretely, the CLR).

Looking forward to the read, thanks :)

By lmeyerov at Mon, 2008-05-05 03:21 | login or register to post comments

[Fixed]

Per request, I edited the story.

By Ehud Lamm at Mon, 2008-05-05 14:17 | login or register to post comments

Three essential transformations

The redacted bits of the post were helpful, I think.

From the paper: "Our technique involves three essential transformations: defunctionalization, ... CPS transformation, and a 'trampoline' that allows tunnelling server-to-client requests within server responses."

Also: "In the future, we hope to extend ... by adding features such as exceptions and generalizing by allowing [the location annotations] to consist of a set of permissible locations. We also hope to implement the ... calculus with location brackets in the Links language."

By ezrakilty at Mon, 2008-05-05 16:02 | login or register to post comments