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Re: N-triples (1.4)

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Wed, 18 Jul 2001 20:26:49 +0100
To: RDF core WG <w3c-rdfcore-wg@w3.org>
cc: Graham Klyne <GK@NineByNine.org>
Message-ID: <13738.995484409@tatooine.ilrt.bris.ac.uk>
>>>Graham Klyne said:
> Re: http://www.w3.org/2001/sw/RDFCore/ntriples/

The file may have moved there but I cannot edit it at present.

> 1. Is it intended that a name can start with a digit?
>    name ::= [A-Za-z0-9]+
> As far as I can tell, it's used only in anonNode

I changed this to match N3 tools but I see now that while
n-triples2kif.pl uses the above, the main cwm code uses
xmllib.py which has:
  _Name = '[a-zA-Z_:][-a-zA-Z0-9._:]*'    # valid XML name

so I guess another change to:
  name ::= [A-Za-z][A-Za-z0-9]*
seems in order.  We probably shouldn't allow _ or : since we use
those in other ways (e.g. would make things like _:_: legal).
I have no opinion about allowing - or .

> 2. I think this violates the syntax notation:
>    absoluteURI ::= [^ < > space]+
> As far as I can tell, http://www.w3.org/TR/REC-xml#sec-notation allows only 
> literal characters or #xN character codes within the [...] construct.  I 
> suggest:
>    absoluteURI ::= ( [^<>] - space )+


I haven't been able to update the document since adding the pointer
to the use of the XML notation, and need to amend the character classes
and references to characters amongst other things.

> 3. Outstanding issue 1
> N-Triples is a text/plain MIME type format - consider character and 
> encoding issues with requirement to be able to express all Unicode chars.
> That much is easy, I think.  Use:
>    Content-type: text/plain;charset=utf-8

That out-of-band information cannot be picked up by the parser just
reading the bytes.  I would prefer the format to be self-contained if
possible, not depending on charset, so all unicode chars can be
handled inside US-ASCII.  Asking N-Triples parsers to have to add an
entire UTF-8 decoding step seems rather an large step, when \u
etc. below could do the work when required.

> 4. Outstanding issue 2
> Consider adding \#xHEX escaping to allow N-Triples to encode Unicode 
> characters in text/plain.  Or after Python: \uxxxx and \Uxxxxxxxx
> I suppose that, for completeness, we must.  Escaping is a topic that can be 
> far trickier than it seems it should be for such a "simple" 
> purpose.  Following your Python reference, I see they've tightened up the 
> Python spec.  I think these are probably the right choices for us:
>    \uxxxx      Character with 16-bit hex value xxxx (Unicode only)
>    \Uxxxxxxxx  Character with 32-bit hex value xxxxxxxx (Unicode only)

I would add notes such that there would only be 1 way to encode any
character, so even escaped literals could be compared as
strings. i.e.
  \uxxxx for (mutter some chars below #0020) & chars #007f-#ffff
  \UXXXXXXXX for chars #00010000 to #ffffffff
> One might also consider allowing:
>    \xhh        ASCII character with hex value hh
> for 'hh' in the range '00' to '7F' (i.e. where Unicode code points match 

Is this one escape too many?  If we do add it, I would prevent \u
from this handling the range this covers.

How about just one escape \UXXXXXXXX for all chars not made available
by \-escapes or used in-situ - that seems more appealing for this
little syntax.

> 5. eoln format
> Being a MIME text/plain format, the cr in eoln should not be optional:
>    eoln ::= cr? lf
> should read:
>    eoln ::= cr lf

As I commented previously, that change would make all our existing
examples illegal and this seems awkward to impose on many people
writing these files.  I would agree if this was a protocol such as
HTTP, SMTP or telnet where it was never (hardly ever) typed by

Most web servers will autodetect and deliver ntriples files as
text/plain whatever line ending we use, for example your RDF Core WG
minutes of 2001-06-15:
is served as text/plain but uses only \n as newlines which strictly
isn't allowed.

So what to do?
Invent a suggested ".nt" suffix and MIME type it text/x-ntriples?

I don't see that as necessary - lets not worry about it.

Received on Wednesday, 18 July 2001 15:26:51 UTC

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