Re: editing -- oops, correction

[Lofton Henderson <lofton@rockynet.com>]

At 06:38 PM 4/10/01 +0200, Dieter Weidenbrueck wrote:
>[...]
>I am not sure whether this change would be correct.
>
>pictseqno is a keyword, whereas picseqno is just a placeholder for a
>character between '0' and '9'. It would have been less confusing to choose a
>different expression for this, but I think it is correct.
>
>[...]
>
>----- Original Message -----
>From: "Cruikshank, David W" <David.Cruikshank@PSS.Boeing.com>
>[...]
> > ok, so I think the editing directive is to change the 2 occurrances of
>picseqno in 3.1.2.1 to pictseqno...I'll go ahead and do that.

I think the change is correct, but the wording of the sections is poor (who 
wrote this stuff?!):

The title of the section is:  "3.1.2.1  Picture Selection 
Keywords".  Clearly, in 1st paragraph 'pictid' is the keyword.  The 
paragraph talks about its value, which is the "id" of the picture.  To be 
consistent, the 2nd pgph should start with the keyword, 'pictseqno'.

Okay, in theory we could change the 1st paragraph, change the section 
title, etc.  But I think it is bad practice to be talking in the text about 
intermediate, non-terminal productions in the BNF -- the "placeholder" as 
you call it.

So let's reword to remove all ambiguity:

### begin ###
pictid - The pictid [Ed: use same font as 1st word] keyword indicates that 
selection of the picture to be viewed is by the id of the picture, which is 
the id parameter in the BEGIN PICTURE element. The picture id value is the 
first, required parameter associated with the keyword (see EBNF), and there 
may be a second associated parameter, which is an optional picture behavior 
specification.  If the metafile does not contain a picture with the 
specified picture id value, the first picture in the metafile is chosen.

pictseqno - The pictseqno [Ed: use same font as 1st word] keyword indicates 
that selection of the picture to be viewed is by the sequence number of the 
picture in the metafile. "1" is the first picture, "2" is the second 
picture, etc. The picture sequence number value is the first, required 
parameter associated with the keyword (see EBNF), and there may be a second 
associated parameter, whose value is an optional picture behavior 
specification.  If the specified picture sequence number value exceeds the 
number of pictures in the metafile, the last picture is displayed.
### end ###

Now, the use of "1" (instead of 1) made me look back to the EBNF.  We 
already have a bug fix to the [0-9]+, to prevent the value 0 (ZERO).  So 
how about this:

picseqno ::= (non-zero-digit)(digit)*
[...]
non-zero-digit ::= "1" | ... | "9"
digit ::= "0" | digit

Of course, this prevents you from writing picture sequence numbers with 
leading zeros, "001".  Does anyone care?  If someone objects to this 
change, then we can leave it as (digit)+ (which is better, I think, than 
[0-9]+), and add to the 3.1.2.1, before the "exceeds number of pictures" 
sentence, "The specified picture sequence number value shall be positive."

Please comment:  option 1 (enforce positive via EBNF change, which has the 
"no leading" ); or, option 2 (enforce positive via words in 3.1.2.1).

Or option 3:  (digit)*(non-zero-digit)(digit)*   (BNF expression for 
positive, leading zeros allowed!).

All,
-Lofton.