- From: Andy Seaborne <andy@apache.org>
- Date: Mon, 29 Dec 2014 13:39:16 +0000
- To: Pat Hayes <phayes@ihmc.us>, Gregg Kellogg <gregg@greggkellogg.com>
- CC: "public-rdf-comments@w3.org" <public-rdf-comments@w3.org>
On 29/12/14 06:31, Pat Hayes wrote: > > On Dec 28, 2014, at 6:10 PM, Gregg Kellogg <gregg@greggkellogg.com> wrote: > >> On Dec 28, 2014, at 3:32 PM, Pat Hayes <phayes@ihmc.us> wrote: >>> >>> >>>> 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? >> >> I share Andy's recollection > > OK, two is enough :-) I bow to your superior recollection, and withdraw my implicit advice to use explicit xsd:string typing. Apologies to all concerned. I went looking (OK, a bit of looking) the first time but couldn't find spec text except the MAY. This discussion was over an extended period. The examples for Turtle are without xsd:string (except to show they are the same). From memory, the line of argument was that simple literals were more common than explicit ^^xsd:string though the community of use is going to be a major factor. Like Gregg, Jena outputs without explicit datatype as the best choice overall. Andy > > Pat > >> , and that is how my serializer behaves. >> Shame that the spec-text doesn't cspture that. >> >> Gregg >> >>>> 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 > > ------------------------------------------------------------ > 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 Monday, 29 December 2014 13:39:50 UTC