Subject: [sv-ac] Re: sequence vs. sequence expression
From: Surrendra Dudani (Surrendra.Dudani@synopsys.com)
Date: Wed Jan 28 2004 - 09:16:26 PST
Hi John,
The words "sequence" and "sequence expression" are semantically synonymous.
"sequence expression" is used to emphasize some manipulation or composition
of expressions, as in the BNF. "sequence" is used when it is referred as a
unit, as in discussing the evaluation in terms of time. However, these are
not consistently used that way.
I'm not sure if it will help to precisely define these terms. It may be
better to use one or the other. After quickly reviewing the LRM, I would
suggest to
1) eliminate the use of word "sequence expression" and just
use "sequence". For exceptions, where we must use sequence expression, we
can specifically state its meaning.
2) We can state that "sequence_expr" from BNF constitutes a sequence, and
that a sequence describes one or more sequential behaviors.
Regarding the paragraph below,
"A sequence expression describes one or more sequences by using regular
expressions. Such a regular expression
can concisely specify a set of zero, finitely many, or infinitely many
sequences that satisfy the sequence
expression."
Can be rewritten as
"A sequence is described as a regular expression. Such a regular expression
can concisely specify a set of zero, finitely many, or infinitely many
sequential behaviors that satisfy the sequence"
Regarding the deletion of "sequence expressions" in the paragraph below, it
seemed redundant to use both terms.
"Sequences and sequence expressions can be composed by concatenation,
analogous to a concatenation of lists.
The concatenation specifies a delay, using ##, from the end of the first
sequence until the beginning of the second
sequence."
Surrendra
At 05:28 PM 1/26/2004 -0600, you wrote:
>Hi Surrendra:
>
>I have some concern about the technical distinction on p. 207
>between "sequence" and "sequence expression". My understanding
>from the first two paragraphs on the page is that a sequence
>is a list of boolean expressions, while a sequence expression
>defines a set of sequences.
>
>I don't think this disctinction is consistent with the way
>these terms are used throughout Section 17.
>
>For example, your change 1.2 strikes "and sequence expressions"
>from the sentence describing concatenation. It therefore
>suggests that sequence expressions cannot be concatenated,
>which is inconsistent with the syntax description in box
>17-3.
>
>My general impression is that in describing the informal
>semantics, "sequence" and "sequence expression" have been
>used interchangeably, while in describing syntax, "sequence
>expression" has usually been preferred.
>
>One possible solution is that we keep the strict distinction
>of sequence and sequence expression and scrub Section 17
>to make certain we use "sequence" only when the restriction
>is appropriate.
>
>Another solution is that we find another term to mean "list of
>boolean expressions", perhaps "simple sequence".
>
>What do you think?
>
>Best regards,
>
>John H.
**********************************************
Surrendra A. Dudani
Synopsys, Inc.
377 Simarano Drive, Suite 300
Marlboro, MA 01752
Tel: 508-263-8072
Fax: 508-263-8123
email: Surrendra.Dudani@synopsys.com
**********************************************
This archive was generated by hypermail 2b28 : Wed Jan 28 2004 - 09:24:13 PST