Talk:Denotational semantics/Archive 1

message: I believe some of the remarks added to the article regarding denotation semantics and concurrency are incorrect. The article suggest atm that denotational semantics is inherently non-concurrent. However, this is not the case: Plotkin shows in his 1997 TCS paper "LCF Considered as a Programming Language" that PCF (the LCF programming language) can be extended with the parallel or and that a denotational model based on domains can be defined for this extended language. Hence, it can be argued that domains already allow for concurrency.
In fact, up until the 1990s it was an active topic of research on how to put extra restrictions onto domains such that only sequential functions are represented (see e.g. Ong's chapter Correspondence between Operational and Denotational Semantics: The Full Abstraction Problem for PCF, in Vol 4 of the Handbook of Logic in Computer Science) -- Koffieyahoo 10:05, 6 September 2005 (UTC)
replies: text: The article cites orginal sources.  Can you cite any errors in the article?--Carl Hewitt 16:28, 6 September 2005 (UTC)

text: Not to detract from Ong's work, it is not an original source.--Carl Hewitt 14:25, 9 September 2005 (UTC)

text: Clinger gave permission in a private message to me.  I suggest that you contact him directly.--Carl Hewitt 14:25, 9 September 2005 (UTC)

text: You can cite overview articles.  I was simply pointing out that they are not original sources.--Carl Hewitt 16:45, 12 September 2005 (UTC)

text: Clinger is the copyright owner.  MIT has the right to distribute.--Carl Hewitt 16:45, 12 September 2005 (UTC)

text: Do you have any particular questions at this point?--Carl Hewitt 16:49, 12 September 2005 (UTC)

text: I agree.--Carl Hewitt 16:45, 12 September 2005 (UTC)
replies: text:  Besides evading many of Koffieyahoo's points, I would also point out that the article completely ignores the contributions of J. de Bakker and his collaborators on the denotational semantics of concurrency.--CSTAR 06:44, 10 November 2005 (UTC)
replies: text: Is any of de Bakker's work on denotational semantics?--Carl Hewitt 07:33, 10 November 2005 (UTC)
thread_title:  Questions about recent additions by CarlHewitt 

message: For starters, you can look at . Please note the following:
* Krzysztof R. Apt, J. W. de Bakker: Exercises in Denotational Semantics. MFCS 1976: 1-11
* J. W. de Bakker: Least Fixed Points Revisited. Theor. Comput. Sci. 2(2): 155-181 (1976)
Not listed there is work by P. America, J. Zucker, de Bakker and others specifically on denotational semantics of concurrency.
* P. America, J. de Bakker, J. N. Kok and J. Rutten: Denotational semantics of a parallel object-oriented language, Information and Computation, 83(2): 152 - 205 (1989)
(This paper actually appeared many years earlier in a technical report published by 
Centrum voor Wiskunde en Informatica
This is one of a series of papers that consider metric space denotational models.  The idea in these papers can be described as finding fixed points of contractive functors on metric categories.
:--CSTAR 17:06, 10 November 2005 (UTC)
replies: text: Samson Abramsky has also done some work in this area.--Carl Hewitt 13:20, 11 November 2005 (UTC)
replies: text: I wasn't aware of any work that Abramsky has done in this specific area (metric space domains), but maybe he has.  Anyway the article is deficient in references, in coverage of the material and in clarity. In particular, I don't think you're use of extensive direct quotes is helpful. Moreover, citing original sources in science does not mean the same thing as it does in history, (including  history of science) since most work in science builds heavily on previous work. I don't see how your response to KoffieYahoo's objections, in which you assert that you cite original sources is relevant.--CSTAR 17:33, 11 November 2005 (UTC)
replies: text: I studied with Abramsky for a couple of years at Imperial in the early 1990s. The article has a slanted POV. Charles Matthews 18:57, 11 November 2005 (UTC)
replies: text:  This article is particularly important, since it is of a foundational nature in COmputer Science. Aside from the intro gives a completely distorted view of denotational semantics. It should at least begin with denotational models for the lambda calculus and relate this to work of Dana Scott and Chris Strachey.  I am willing to do this myself, although I would be very appreciative if someone else did this; I would like to avoid another confrontation with Hewitt. Thanks.--CSTAR 21:24, 11 November 2005 (UTC)
replies: text: Of course you realize that the lambda calculus models are submodels of Actor models in which the arrival ordering of messages sent to Actors is not visible.  Nevertheless this is a useful special case that deserves treatment.--Carl Hewitt 10:54, 21 November 2005 (UTC)
replies: text:  Nobody is disputing the generality of the actor model of computation and its ability to model various things such as concurrency and indeterminism. However, your approach makes about as much sense as to claim that to address (a):  provide a denotational semantics for the lamba calculus it would suffice to achieve (b) provide  a denotational model for Turing machines (including a definition of what this means).  The exercise (b), though quite interesting, would not adequately address (a).--CSTAR 17:35, 21 November 2005 (UTC)
thread_title:  Reply to Hewitt 

message: Is this section properly titled? Semantics is a function from a set of syntactic objects into a semantic domain. In what sense are you giving semantics of a function. I'm not against using imprecise language, but I think these examples should be presented carefully. I'm not sure how to rename the section, but its current title is confusing.--CSTAR 05:42, 12 November 2005 (UTC)
replies: text: I concur.  What do you think of "Denotational semantics of functional programs"?--Carl Hewitt 05:52, 12 November 2005 (UTC)
replies: text:  That probably is better. The example you give is a functional (i.e., non imperative) program.--CSTAR 06:02, 12 November 2005 (UTC)
replies: text: I made the change.  Thanks for noticing this.--Carl Hewitt 14:08, 12 November 2005 (UTC)
replies: text:  The example is still confusing; It defines the meaning of a recursive functional program.--CSTAR 18:21, 12 November 2005 (UTC)
replies: text: I don't quite understand what you find confusing.  Thanks,--Carl Hewitt 13:23, 13 November 2005 (UTC)
thread_title: Denotational semantics of functions 

message: I would like to apologize to CSTAR for the tone of 2 of my remarks in our recent discussion above on delayed evaluation:
:#I suppose that you have realized by now ...
:#I don't think that you quite understand the problem here ...
These remarks were not collegial and I will strive to do better in the future.
Regards,--Carl Hewitt 06:46, 24 November 2005 (UTC)
thread_title:  Apology to [[User:CSTAR|CSTAR]]