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Re: decimals in Turtle tests

From: Alex Hall <alexhall@revelytix.com>
Date: Tue, 28 Feb 2012 14:38:44 -0500
Message-ID: <CAFq2biw+PN+_090D-oEO=YHJeraS78mdZdCTaWeWtxeYCQ2VvQ@mail.gmail.com>
To: Henry Story <henry.story@bblfish.net>
Cc: public-rdf-comments@w3.org
On Tue, Feb 28, 2012 at 2:04 PM, Henry Story <henry.story@bblfish.net>wrote:

> I just found that the test suite is assuming there is a maximum
> precision for xsd:decimals
> In these test suites
> http://www.w3.org/TR/turtle/tests/test-28.ttl
> http://www.w3.org/TR/turtle/tests/test-28.out
> we can find that after a number of 00s the numbers are suddenly simplified
>  "2.234000000000005"^^<http://www.w3.org/2001/XMLSchema#decimal> .
>  "2.2340000000000005"^^<http://www.w3.org/2001/XMLSchema#decimal> .
>  "2.234"^^<http://www.w3.org/2001/XMLSchema#decimal> .
>  "2.234"^^<http://www.w3.org/2001/XMLSchema#decimal> .
> I could not find in the xsd spec anything about this, neither in the
> rdf semantics specification.  Is this an error, or is this a byproduct
> of a specific implementation?

xsd:float and xsd:double are modeled after IEEE 32 and 64-bit floating
point numbers, so they do have a maximum precision. Perhaps one of these
was intended?

Regardless of the specific datatype, I don't think these cases involving
precision of floating-point numbers belong as part of the Turtle test
suite. The Turtle specification says nothing about interpretation of
datatypes, XSD or otherwise, nor about canonicalization of the lexical
form. The tests should only concern themselves with issues of Turtle
syntax, and precision of xsd:float/double values is well outside the scope
of that.

After all, "dog"^^xsd:integer is a perfectly valid RDF literal and should
be allowed in a Turtle file. It's not until you get into issues of datatype
interpretation that you care whether "dog" is a valid integer.


> Henry
> http://www.w3.org/TR/xsd-precisionDecimal/#precisionDecimal
> Social Web Architect
> http://bblfish.net/
Received on Tuesday, 28 February 2012 19:39:33 UTC

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