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Re: Minus signs in ids -- n3.bnf

From: Tim Berners-Lee <timbl@w3.org>
Date: Wed, 5 Dec 2001 17:08:40 -0500
Message-ID: <013101c17dd9$65d81600$0301a8c0@w3.org>
To: "Petr Cimprich" <petr@gingerall.cz>
Cc: "Sandro Hawke" <sandro@roads.org>, <www-archive@w3.org>
Petr,

----- Original Message -----
From: "Petr Cimprich" <petr@gingerall.cz>
To: "Tim Berners-Lee" <timbl@w3.org>
Cc: "Sandro Hawke" <sandro@roads.org>; <www-archive@w3.org>
Sent: Wednesday, December 05, 2001 7:59 AM
Subject: Re: Minus signs in ids -- n3.bnf


> Tim, Sandro
>
> Thanks for the reply. The escaping is a good idea, but it doesn't work
> in both ways. I mean that "-" in XML would be mapped to "__" in N3, but
> it likely remains "__" if converted back to XML.

No, the mapping is 1:1 and therefore the inverse mapping would
have to be used the other way.

> However, it's still
> better than to exclude names with "-" completely.
>
> May be I'm wrong, but since operators are to be used as shorthands for
> properties and there is always at least one space between subject and
> verb, or verb and object, a hyphen in local names (something like
> "pref:local-name") should never be taken as operator. But it's quite
> possible I'm missing your idea of operators at all.

Well, what is allowed depends on how they are addedto the language.
Many people would find the necessity of leaving spaces around an operator
unnatural -- and therefore error-prone.

> Anyway, I see that my former suggestion to change alphanumeric wasn't
> necessary. Instead, the following change would apply to local names only:
>
> fragid ::= alpha alphanumeric* ;
> to
> fragid ::= alpha ( alphanumeric  |  "-" )* ;

yes. that is what one would do.

May I copy this message to www-rdf-interest@w3.org, the RDF interest group?
Tim BL
> Have a nice day,
> Petr
>
>
> Tim Berners-Lee wrote:
>
> >Peter,
> >
> >Sandro passed on your message.
> >
> >Adding "-" to the ID characters is a problem, in that I wanted to reserve
> >the usual operators for use as operators in some posisble future
shorthand
> >notation.
> >
> >Another solution would be to have some form of escaping,
> >such as mapping sequences of "-" into sequences of "_" in some way,
> >such as taking a contiguous sequence of - and _,
> >replacing  _ with 0 and - with 1, then adding a leading "1",
> >taking what you have as a binary number, subtracting
> >1 from the result, and then writing that many _ signs.
> >The mapping is 1:1, and maps the simple case of - onto __
> >and _ onto _.
> >
> >The only disadvantage is that those who co crazy with
> >n consecutive occurrences of  - and/or _  in XML will pay for it
> >in an even crazier 2**n long sequence in the N3.
> >
> >I'll put a note in the Notation3 document suggesting this.
> >
> >Tim
> >
> >----- Original Message -----
> >From: "Sandro Hawke" <sandro@roads.org>
> >To: <timbl@w3.org>
> >Sent: Tuesday, December 04, 2001 10:02 AM
> >Subject: Petr Cimprich: n3.bnf
> >
> >
> >>Tim, I think he's suggesting allowing "-" in n3 identifiers, which I
> >>think you don't want because you want to keep it as a possible
> >>operator.   I'll reply if I don't see some reply from you to him soon.
> >>
> >>    -- sandro
> >>
> >>------- Forwarded Message
> >>
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> >>Date: Tue, 04 Dec 2001 14:43:20 +0100
> >>From: Petr Cimprich <petr@gingerall.cz>
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> >>
> >>Sandro,
> >>
> >>I have have written an N3 parser in Perl a while ago according to your
> >>BNF def
> >>
>
>(http://dev.w3.org/cvsweb/2001/blindfold/sample/n3.bnf?rev=1.4&content-type
=
> >text/x-cvsweb-markup).
> >
> >>
> >>I have an issue I have encountered during conversions to and from XML:
> >>While XML allows to use a hyphen in names, it is prohibited in N3
> >>localname. How about to change
> >>
> >>alphanumeric ::= alpha | [0-9] | "_";
> >>
> >>to
> >>
> >>alphanumeric ::= alpha | [0-9] | "_" | "-";
> >>
> >>Would it mind anything? Hyphen doesn't seem to have any special meaning
> >>in N3.
> >>
> >>Thanks a lot for your time,
> >>Petr
> >>
> >>- --
> >>Petr Cimprich
> >>Ginger Alliance
> >>www.gingerall.com
> >>
> >>
> >>------- End of Forwarded Message
> >>
> >
>
> --
> Petr Cimprich
> Ginger Alliance
> www.gingerall.com
>
>
>
Received on Wednesday, 5 December 2001 17:04:29 GMT

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