ISSUE-129: JSON-LD xsd:integer lossless conversion
LC2 - Hawke - Native Type Conversion
JSON-LD xsd:integer lossless conversion
- State:
- CLOSED
- Product:
- JSON-LD Last Call 2
- Raised by:
- Sandro Hawke
- Opened on:
- 2013-05-13
- Description:
- JSON-LD-API allows certain RDF literals to be mapped to JSON numbers (if
the "use native types" flag is set), but I don't think the mapping rules
are as good as they could be. Markus concurs, although I'm not sure we
quite agree on what they should be.
The current spec says:
If the /use native types/ flag is set to true
<http://www.w3.org/TR/json-ld-api/#dfn-true>, RDF literals
<http://www.w3.org/TR/rdf11-concepts/#dfn-literal> with a datatype
IRI <http://www.w3.org/TR/rdf11-concepts/#dfn-datatype-iri> that
equals |xsd:integer| or |xsd:double| are converted to a JSON numbers
<http://www.w3.org/TR/json-ld-api/#dfn-number>
...
if the datatype IRI
<http://www.w3.org/TR/rdf11-concepts/#dfn-datatype-iri> of /value/
equals |xsd:integer| or |xsd:double| and its lexical form
<http://www.w3.org/TR/rdf11-concepts/#dfn-lexical-form> is a valid
|xsd:integer| or |xsd:double| according [XMLSCHEMA11-2
<http://www.w3.org/TR/json-ld-api/#bib-XMLSCHEMA11-2>], set
/converted value/ to the result of converting the lexical form
<http://www.w3.org/TR/rdf11-concepts/#dfn-lexical-form> to a JSON
number <http://www.w3.org/TR/json-ld-api/#dfn-number>.
...
It is important to highlight that in practice it might be impossible
to losslessly convert an |xsd:integer| to a number
<http://www.w3.org/TR/json-ld-api/#dfn-number> because its value
space is not limited.
There is a test case:
https://github.com/json-ld/json-ld.org/blob/master/test-suite/tests/fromRdf-0002-in.nq
https://github.com/json-ld/json-ld.org/blob/master/test-suite/tests/fromRdf-0002-out.jsonld
Now, that warning about lossless conversion can be rendered unnecessary,
I believe, by saying in situations where there might be a loss, one MUST
NOT convert to a number. It's true we don't know exactly when there
might be a loss, but after talking with Markus, I'm pretty confident
that using the range of 32-bit integers will work well. JavaScript
requires 64-bit IEEE, so it can handle intergers up to 53-bits, and
other systems like PHP (on 32-bit systems) use 32-bit ints for (integer)
numbers. I propose an additional test case showing:
"-2147483649"^^xs:integer // not native since it's outside the 32-bit range
"-2147483648"^^xs:integer // native json number
"2147483647"^^xs:integer // native json number
"2147483648"^^xs:integer // not native since it's outside the 32-bit range
I'd also add:
"1"^^xs:int // not native since it's 'int' not 'integer'
"01"^^xs:integer // not native since it's not in canonical form
These rules will make xs:integer data round tripping through JSON-LD
perfectly lossless, I believe, on systems that can handle at least 32
bit integers.
I'm paying attention to this mostly because I'm building RDF data
synchronization stuff in JavaScript. I need the code to not corrupt
data (even seemingly harmless corruption will screw up synchronization),
and I'd like to align it with JSON-LD.
On a related topic, there's still the problem of xs:double. I don't
have a good solution there. I think the only way to prevent datatype
corruption there is to say don't use native number when the value
happens to be an integer. But that's pretty painful -- you don't want
different code paths just because the value happens to be an integer.
:-/ (Or have a custom JSON parson that notices the ".0".... but
that's kind of against the rules. Maybe we could suggest it for cases
that need type fidelity? I don't know.)
Original post:
http://lists.w3.org/Archives/Public/public-rdf-wg/2013May/0121.html
- Related Actions Items:
- No related actions
- Related emails:
- Official response to RDF-ISSUE-129: xsd:integer lossless conversion (from msporny@digitalbazaar.com on 2013-08-13)
- JSON-LD Telecon Minutes for 2013-06-04 (from msporny@digitalbazaar.com on 2013-06-06)
- RE: Agenda: JSON-LD Telecon - Tuesday, June 4th 2013 (from markus.lanthaler@gmx.net on 2013-06-02)
- Agenda: JSON-LD Telecon - Tuesday, June 4th 2013 (from msporny@digitalbazaar.com on 2013-06-02)
- RE: Agenda: JSON-LD Telecon - Tuesday, May 28th 2013 (from markus.lanthaler@gmx.net on 2013-05-27)
- Agenda: JSON-LD Telecon - Tuesday, May 28th 2013 (from msporny@digitalbazaar.com on 2013-05-26)
- Re: JSON-LD Telecon Minutes for 2013-05-14 / RDF-ISSUE-128 and RDF-ISSUE-129 (from gregg@greggkellogg.net on 2013-05-19)
- RE: JSON-LD Telecon Minutes for 2013-05-14 / RDF-ISSUE-128 and RDF-ISSUE-129 (from markus.lanthaler@gmx.net on 2013-05-19)
- Re: JSON-LD Telecon Minutes for 2013-05-14 / RDF-ISSUE-128 and RDF-ISSUE-129 (from gregg@greggkellogg.net on 2013-05-19)
- RE: JSON-LD Telecon Minutes for 2013-05-14 / RDF-ISSUE-128 and RDF-ISSUE-129 (from markus.lanthaler@gmx.net on 2013-05-19)
- Re: JSON-LD Telecon Minutes for 2013-05-14 / RDF-ISSUE-128 and RDF-ISSUE-129 (from ansell.peter@gmail.com on 2013-05-19)
- Agenda: JSON-LD Telecon - Tuesday, May 21st 2013 (from msporny@digitalbazaar.com on 2013-05-19)
- RE: JSON-LD Telecon Minutes for 2013-05-14 / RDF-ISSUE-128 and RDF-ISSUE-129 (from markus.lanthaler@gmx.net on 2013-05-18)
- JSON-LD Telecon Minutes for 2013-05-14 (from msporny@digitalbazaar.com on 2013-05-14)
- Re: RDF-ISSUE-129 Re: json-ld-api: change proposal for handling of xs:integer (from sandro@w3.org on 2013-05-13)
- RE: RDF-ISSUE-129 Re: json-ld-api: change proposal for handling of xs:integer (from markus.lanthaler@gmx.net on 2013-05-13)
- Re: RDF-ISSUE-129 Re: json-ld-api: change proposal for handling of xs:integer (from sandro@w3.org on 2013-05-13)
- RE: RDF-ISSUE-129 Re: json-ld-api: change proposal for handling of xs:integer (from markus.lanthaler@gmx.net on 2013-05-13)
- Re: RDF-ISSUE-129 Re: json-ld-api: change proposal for handling of xs:integer (from gregg@greggkellogg.net on 2013-05-13)
- RE: Agenda: JSON-LD Telecon - Tuesday, May 14th 2013 (from markus.lanthaler@gmx.net on 2013-05-13)
- RDF-ISSUE-129 Re: json-ld-api: change proposal for handling of xs:integer (from sandro@w3.org on 2013-05-13)
- RDF-ISSUE-129 (LC2 - Sandro Hawke): JSON-LD xsd:integer lossless conversion [JSON-LD Last Call 2] (from sysbot+tracker@w3.org on 2013-05-13)
- Agenda: JSON-LD Telecon - Tuesday, May 14th 2013 (from msporny@digitalbazaar.com on 2013-05-12)
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