- From: Pat Hayes <phayes@ihmc.us>
- Date: Sun, 28 Dec 2014 17:31:02 -0600
- To: Andy Seaborne <andy@apache.org>
- Cc: public-rdf-comments@w3.org
On Dec 28, 2014, at 5:40 AM, Andy Seaborne <andy@apache.org> wrote: > On 28/12/14 05:04, Pat Hayes wrote: >> >> On Dec 27, 2014, at 9:24 PM, Stian Soiland-Reyes <soiland-reyes@cs.manchester.ac.uk> wrote: >> >>> No, for once I am not coming from OWL :) >>> >>> I'm just writing a simple n-triples serializer, and I am not sure if I should simply always include the type if there is no @lang (e.g. ^^xsd:string) >> >> It was certainly the intention of the RDF 1.1 WG that every literal should have a type. We even provided a special 'type' for the @lang case, to preserve this intention. It seems to me that one should not ever go wrong by including the ^^xsd:string, which was semantically correct even in original RDF, whereas really plain plain literals now have the shadow of deprecation hanging over them, at the very least. >> >> Hope this helps. >> >> Pat Hayes > > And for serialization, the WG intention IIRC was that all ^^xsd:strings should be written without the ^^xsd:string in all formats where possible. Really? I have no recollection of that, but I may have missed some discussions. Can you find this in the minutes or emails anywhere? > It look nicer. Maybe, but it also can produce uncertainty, as for example: "Before rdf 1.1 the norm tended to be to NOT express xsd:string unless it really was a character-by-character string (e.g. a genome identifier), and not when it was human text (but in unknown or mixed language)." Even in RDF 1.0, plain literals were specified to be semantically identical to xsd:string-typed literals, but this was buried in the semantics dociument which nobody read, and because the syntactic distinction was available, people assumed it meant something. As long as a syntax offers both choices, this misreading process will continue to operate, even now RDF 1.1 has said explicitly that plain literals are only syntactic sugar for the typed version. > http://www.w3.org/TR/rdf11-concepts/#section-Graph-Literal only says "MAY" -- that is mainly so as not to suggest much RDF 1.0 data output by pre-existing software is suddenly invalidated, which it isn't. Certainly, plain literal surface syntax is not *invalidated* by RDF 1.1. Sorry if I gave that impression. Pat > > Andy > > >> >>> ..Or if I should have a special case to output anything with type xsd:string as a classic "plain literal", e.g. no @ or ^^. >>> >>> Surely just one of these should be in the canonical version ? My guts says to always include the type for non-lang, but the spec is ambigous on this - if xsd:string is implied, should I then prefer to generate this implied version? >>> >>> Before rdf 1.1 the norm tended to be to NOT express xsd:string unless it really was a character-by-character string (e.g. a genome identifier), and not when it was human text (but in unknown or mixed language). >>> >>> As we SHOULD be generating the Canonical N-Triples, then it would be good to know if there already is a silent de facto agreement that is just not expressed in the spec. >>> >>> You might know the code base - >>> https://github.com/stain/commons-rdf/blob/tests/src/test/java/com/github/commonsrdf/dummyimpl/LiteralImpl.java#L99 >>> >>> On 27 Dec 2014 17:14, "Peter Ansell" <ansell.peter@gmail.com> wrote: >>> Hi Stian, >>> >>> RDF-1.1 does not have the concept of plain literals [1]. Hence, it is >>> difficult to map the OWL-WG-derived rdf:PlainLiteral set to RDF-1.1, >>> if that is where you are coming at the issue from [2]. >>> >>> Cheers, >>> >>> Peter >>> >>> [1] http://www.w3.org/TR/2014/REC-rdf11-concepts-20140225/#section-Graph-Literal >>> [2] https://github.com/owlcs/owlapi/issues/172 >>> >>> On 27 December 2014 at 16:37, Stian Soiland-Reyes >>> <soiland-reyes@cs.manchester.ac.uk> wrote: >>>> In http://www.w3.org/TR/n-triples/#canonical-ntriples I read: >>>> >>>>> Canonical N-Triples has the following additional constraints on layout: >>>>> >>>>> The whitespace following subject, predicate, and object MUST be a single space, (U+0020). All other locations that allow whitespace MUST be empty. >>>>> There MUST be no comments. >>>>> HEX MUST use only uppercase letters ([A-F]). >>>>> Characters MUST NOT be represented by UCHAR. >>>>> Within STRING_LITERAL_QUOTE, only the characters U+0022, U+005C, U+000A, U+000D are encoded using ECHAR. ECHAR MUST NOT be used for characters that are allowed directly in STRING_LITERAL_QUOTE. >>>> >>>> >>>> and in http://www.w3.org/TR/n-triples/#sec-parsing-terms >>>> >>>>> If neither a language tag nor a datatype IRI is provided, the literal has a datatype of xsd:string. >>>> >>>> >>>> and in http://www.w3.org/TR/n-triples/#sec-literals >>>> >>>>> If there is no datatype IRI and no language tag it is a simple literal and the datatype is http://www.w3.org/2001/XMLSchema#string. >>>> >>>>> Example 3 >>>>> <http://example.org/show/218> <http://www.w3.org/2000/01/rdf-schema#label> "That Seventies Show"^^<http://www.w3.org/2001/XMLSchema#string> . # literal with XML Schema string datatype >>>>> <http://example.org/show/218> <http://www.w3.org/2000/01/rdf-schema#label> "That Seventies Show" . # same as above >>>> >>>> >>>> So I am not any wiser with regards to how to serialize plain literals >>>> in RDF 1.1 Canoical N-Triples.. >>>> >>>> >>>> Are both of the two examples allowed in Canonical N-Triples? (it seems >>>> so by the spec.. :-( ). >>>> >>>> Which variant should I generate? >>>> >>>> >>>> -- >>>> Stian Soiland-Reyes, myGrid team >>>> School of Computer Science >>>> The University of Manchester >>>> http://soiland-reyes.com/stian/work/ http://orcid.org/0000-0001-9842-9718 >>>> >> >> ------------------------------------------------------------ >> IHMC (850)434 8903 home >> 40 South Alcaniz St. (850)202 4416 office >> Pensacola (850)202 4440 fax >> FL 32502 (850)291 0667 mobile (preferred) >> phayes@ihmc.us http://www.ihmc.us/users/phayes ------------------------------------------------------------ IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32502 (850)291 0667 mobile (preferred) phayes@ihmc.us http://www.ihmc.us/users/phayes
Received on Sunday, 28 December 2014 23:31:55 UTC