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Re: Are spaces allowed between terms in N-Triples 1.1?

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Wed, 28 Jun 2017 17:31:00 -0700
To: Gregg Kellogg <gregg@greggkellogg.net>, Wouter Beek <w.g.j.beek@vu.nl>
Cc: SW-forum Web <semantic-web@w3.org>
Message-ID: <bd84ac54-69af-3f69-5d4e-2eeb92515a24@gmail.com>
It is not possible for N-Triples parsers to be overly lenient, nor is it
possible for Turtle parsers to be overly lenient.   The Turtle specification
has a note in Section 5 on this point.

However, even though everything you say below is true, it is still the case
that the grammar sections in both the N-Triples document and the Turtle
document are incorrect and need to be rewritten.

It is also not clear that every valid N-Triples document is a valid Turtle

Peter F. Patel-Schneider
Nuance Communications

On 06/28/2017 04:48 PM, Gregg Kellogg wrote:
> Whitespace is typically taken to zero or more characters of whitespace. Note in the Change Log [1]:
>> White space rules defined outside of grammar, as in Turtle [2], although the N-Triples grammar restricts White space to tab or (tab U+0009 or space U+0020).
> If N-Triples parsers are overly lenient in allowing multiple whitespace characters between terminals, then by that logic, so are Turtle parsers.
> The restriction that terminals be separated by exactly a single whitespace is true for the Canonical form of N-Triples [3]. Tokenizers only require whitespace to distinguish two terminals that would otherwise be joined.
> Furthermore, there is a minimal whitespace test [4] that verifies that this is the intention of the working group.
>    <http://example/s><http://example/p><http://example/o>.
>    <http://example/s><http://example/p>"Alice".
>    <http://example/s><http://example/p>_:o.
>    _:s<http://example/p><http://example/o>.
>    _:s<http://example/p>"Alice".
>    _:s<http://example/p>_:bnode1.
> There is also the original N-Triples test [5] that contains many instances of terminals separated by mutliple whitespace characters [5], for example:
>     # spaces and tabs throughout:
>          <http://example.org/resource3>          <http://example.org/property>   <http://example.org/resource2>         .        
> Gregg Kellogg
> gregg@greggkellogg.net
> [1] https://www.w3.org/TR/n-triples/#changes-between-last-call-working-draft-and-publication-as-note
> [2] https://www.w3.org/TR/turtle/#grammar-production-WS
> [3] https://www.w3.org/TR/n-triples/#canonical-ntriples
> [4] http://w3c.github.io/rdf-tests/ntriples/lantag_with_subtag.nt
>> On Jun 28, 2017, at 8:58 AM, Peter F. Patel-Schneider <pfpschneider@gmail.com> wrote:
>> This means that all existing N-Triples parsers are lenient in that they
>> process documents that are not valid N-Triples documents.  This, however, does
>> not make them too lenient as there is no requirement that an N-Triples
>> processor reject inputs that are not N-Triples documents.
>> This does mean that Canonical N-Triples documents are not valid N-Triples
>> documents.
>> peter
>> PS:  Of course what it really means is that the grammar section of the
>> N-Triples document needs to be changed.
>> On 06/28/2017 08:50 AM, Wouter Beek wrote:
>>>> So it seems to me that spaces are not allowed anywhere in [1] in N-Triples, i.e.,
>>>> <x:y> <x:y> <x:y> .
>>>> is not a valid N-Triples triple.
>>> I do follow your reasoning here, but this would mean that all existing
>>> N-Triples parsers are too lenient.
Received on Thursday, 29 June 2017 00:31:36 UTC

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