Re: Semantics, opt in Semantics

wclodius@earthlink.net (William Clodius)
Fri, 16 Jan 2015 12:22:21 -0700

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Related articles
Semantics, opt in Semantics seimarao@gmail.com (Seima Rao) (2015-01-15)
Re: Semantics, opt in Semantics rpw3@rpw3.org (2015-01-16)
Re: Semantics, opt in Semantics kaz@kylheku.com (Kaz Kylheku) (2015-01-16)
Re: Semantics, opt in Semantics haberg-news@telia.com (Hans Aberg) (2015-01-16)
Re: Semantics, opt in Semantics wclodius@earthlink.net (2015-01-16)
Re: Semantics, opt in Semantics gah@ugcs.caltech.edu (glen herrmannsfeldt) (2015-01-17)
Re: Semantics, opt in Semantics monnier@iro.umontreal.ca (Stefan Monnier) (2015-01-18)
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From: wclodius@earthlink.net (William Clodius)
Newsgroups: comp.compilers
Date: Fri, 16 Jan 2015 12:22:21 -0700
Organization: Compilers Central
References: 15-01-013
Keywords: semantics
Posted-Date: 17 Jan 2015 02:13:20 EST

Seima Rao <seimarao@gmail.com> wrote:


> The Backus Naur Form is a great mathematical model. It explains syntax
> quite succintly.
>
> In that form, the opt qualifier which stands for optional or
> epsilon is utilized extensively for optional syntax.
>
> Is there something similar for semantics i.e. is there something optional
> in semantics.
>
> Also, what is the equivalent in semantics of BNF ?
>
> Sincerely,
> Seima Rao.
> [Man, there's a can of worms. There's no semantic formalism that matches real
> semantics as well as BNF matches real syntax. -John]


This seems to combine three separate questions:


1. What notations are available for semantic descriptions?


2. What semantic concepts are considered optional?


3. How are those optional concepts expressed in the semantic notations?


As to the first question the complexity of semanticsx has resulted in a
large variety of notations: the van Wijngaarden two level grammar, the
Vienna Definition Language/Vienna Development Method, Denotational
semantics, attribute grammars,etc.


As to the second some obvious optional semantics include parallelism,
and side effects including exceptions and some forms of I/O.


I believe the latter reports on Algol68 included parallelism defined in
the van Wijngaarden two level grammar.


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