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ISSUE-69 (datatype sizes): datatype sizes

From: RDB2RDF Working Group Issue Tracker <sysbot+tracker@w3.org>
Date: Fri, 30 Sep 2011 14:36:09 +0000
To: public-rdb2rdf-wg@w3.org
Message-Id: <E1R9eC9-0004OS-GC@barney.w3.org>

ISSUE-69 (datatype sizes): datatype sizes

http://www.w3.org/2001/sw/rdb2rdf/track/issues/69

Raised by: Eric Prud'hommeaux
On product: 

http://www.w3.org/2001/sw/rdb2rdf/track/issues/48 was resolved by following the SQL spec's lead for generating XML from SQL datatypes. Unfortunately, these mappings are all subject to vender-specific width limitations, which means that implementors have no idea what to implement in order to interoperate with other implementations. The Direct Mapping LC provides fixed numbers for these mappings,
  http://www.w3.org/TR/2011/WD-rdb-direct-mapping-20110920/#defn-literal_map
but these have not been subject to WG review. Justifications for these selections were:
  type       width  reason
  xsd:decimal  18   http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#decimal says minimum is 18
  xsd:integer  18   lexical restriction of decimal doesn't affect width
  xsd:double   23   maximum characters for an IEEE754 double (i.e. xsd:double)
  xsd:date     13   limited to under 100k years, e.g. +100000-01-01
  xsd:time     23   10E-14 second precision, e.g. 01:23:45.67890123456789
  xsd:dateTime 37   sizeof(xsd:date)+sizeof("T")+sizeof(xsd:time)

The choices of 10E6 years and 10E-14 seconds are arbitrary. We could limit to common cases like CCYY for years, and microsecond precision for time, noting that extensions to dates should follow the conventions in ISO8601. That would reduce widths to 10 and 15, putting dateTimes as 26.
Received on Friday, 30 September 2011 14:36:10 UTC

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