[wg11] [Fwd: Re: express question about case]

[Ed Barkmeyer]

I am not authorized to post to AP-INTEROP-L, but this issue should have 
been raised on the WG11 exploder anyway.

-------- Original Message --------
Subject: Re: express question about case
Date: Tue, 23 Oct 2007 13:56:51 -0400
From: Ed Barkmeyer <edbark at nist.gov>
Reply-To: edbark at nist.gov
Organization: NIST
To: Allison Barnard Feeney <abf at CME.NIST.GOV>
CC: AP-INTEROP-L at ATICORP.ORG,  Steve Waterbury 
<stephen.c.waterbury at nasa.gov>
References: <93EE625F-5D88-4DA1-9A62-4C2AA029C222 at cme.nist.gov>

Allison Barnard Feeney wrote:
> Phil, Jochen,
> 
> Trying to resolve an issue of case in Part 11.  7.1.2 states case is 
> significant only if ... but then the syntax production contains only 
> lowercase latters.  Is this a contadiction?  Tony Ranger is interpreting 
> the syntax to mean upper case letters are not allowed.  Advice appreciated.
> Allison
> 
>  From part11e2is
> 
> 7.1.2 Letters 
> EXPRESS uses the upper and lower case letters of the English alphabet 
> (cells 41 - 5A and 61 - 
> 7A of the EXPRESS character set). The case of letters is significant 
> only within explicit string 
> literals. 
> NOTE EXPRESS may be written using upper, lower or mixed case letters 
> (see example 7). 
> Syntax: 
> 128 letter = ’a’ | ’b’ | ’c’ | ’d’ | ’e’ | ’f’ | ’g’ | ’h’ | ’i’ | ’j’ | 
> ’k’ | ’l’ | 
> ’m’ | ’n’ | ’o’ | ’p’ | ’q’ | ’r’ | ’s’ | ’t’ | ’u’ | ’v’ | ’w’ | ’x’ | 
> ’y’ | ’z’ . 
> 
> 
> Allison Barnard Feeney
> National Institute of Standards and Technology
> 100 Bureau Drive
> Gaithersburg, MD  20899-8260
> v.  301-975-3181
> f.  301-975-4694
> e. abf at nist.gov <mailto:abf at nist.gov>

Whilst my opinion was not solicited, I thought this was pretty clear
from the standard, even if it is badly written.

The lexical production rule says there are 26 distinct terminals that
satisfy "letter".  The text above it says that each of those 26 terminal
symbols has two possible character-code representations in the text of
the EXPRESS schema -- the lower-case representation and the upper-case
representation.  And the text explicitly says that cells 41-5A (the 
upper case representations) are valid letters.

The intent of 7.1.2 is:

"EXPRESS uses the 26 letters in the English alphabet in identifiers and
reserved words.  In identifiers and reserved words, the upper or lower
case of letters is not significant.  That is, cells 41 - 5A of the 
EXPRESS character set are treated as alternative representations of 
cells 61 - 7A of the EXPRESS character set.  Each letter has two 
allowable representations.

Note: The two distinct representations of the letters are treated as
distinct characters when they occur in a string_literal.  That is, the
case of letters is significant in a string literal."


Unfortunately, since the non-terminal "letter" is also used in defining
string-literal, the characters are not distinguishable in a
string-literal either.  The production rule must have a consistent
interpretation.

So there is a defect in Part 11.  Production rule 134 (not-quote) should
not refer to the production for "letter" at all!  It should simply
enumerate all the allowable characters, including both lower-case
letters and upper-case letters.

I also read 7.1.2 to say that the case of letters is not significant in
remarks, either, and that is probably incorrect.  Since they are treated
as whitespace, no character of a remark has significance with respect to
the interpretation of a schema.  But whatever the significance of
attaching a remark to a model element is, the significance of case in
the letters in that remark is certainly up to the annotator.  So I would
argue that this is also a defect.  What is really wanted is a production
for not-quote-paren-or-star that enumerates all the other characters and
does not appeal to digit or letter or any production with lexical
significance.

-Ed


-- 
Edward J. Barkmeyer                        Email: edbark at nist.gov
National Institute of Standards & Technology
Manufacturing Systems Integration Division
100 Bureau Drive, Stop 8263                Tel: +1 301-975-3528
Gaithersburg, MD 20899-8263                FAX: +1 301-975-4694

"The opinions expressed above do not reflect consensus of NIST,
  and have not been reviewed by any Government authority."