Re: Minutes of Oct 4 RDB2RDF Telcon

* Richard Cyganiak <richard@cyganiak.de> [2011-10-11 14:01+0100]
> Eric,
> 
> I maintain my -1 to any design that asks a conforming DM implementation that operates over a conforming SQL-2008 implementation to discard information.

The Direct Graph is defined for data where we can expect interoperability. This covers all of the use cases in our Use Cases document, and frankly, every use case I've seen outside of certain exotic gene databases. I think we're well past an 80/20 compromise here.

There is text suggesting correct behavior for extensions which exceed this space:
[[
Extensions to the Direct Mapping should note the spirit of this mapping, i.e. to use a valid representation of an XML Schema Datatype corresponding to the SQL datatype. For numerics, booleans and dates, the canonical XML Schema lexical representation is used. Extensions are likely to map data outside of the minimal SQL conformance into data types with higher precision than those specified by the literal map.
]]

I believe the "data types with higher precision" sentence addresses the data you wish to preserve without claiming that it's in the core language. The text about using "a valid representation of an XML Schema Datatype" directs those who wish to represent data types we've not covered, as well as those outside the SQL range (e.g. the year before 0001 should be -0001, not 0000¹).

Directing extensions to use XSD provides more interoperability than simply capturing the vendor-specific lexical form of SQL extensions for e.g. dateTimes (which may or may not have a year 0000).

I'd like editorial suggestions, as well as advice from the WG about whether we should materialize the ellusive minimal intersection between SQL and XSD so that others don't have to do it:

decimal  18 digits per XSD
integer  18 digits per XSD
double   '±' + 16ch mantissa + 4ch exp per IEEE754  // what to do with NAN, +∞, −∞?
date     4 digits per SQL
time     hh:mm:ss.mmmmmm per SQL

¹http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/#year-zero


> Best,
> Richard
> 
> 
> On 11 Oct 2011, at 03:04, Eric Prud'hommeaux wrote:
> 
> > * ashok malhotra <ashok.malhotra@oracle.com> [2011-10-04 10:14-0700]
> >> Minutes of Oct 4 RDB2RDF Telcon are at http://www.w3.org/2011/10/04-RDB2RDF-minutes.html
> > 
> > per the action implied by
> > [[
> > Ashok: "if your datatypes are inside of SQL *AND* XSD, this is the behavior. if not, it's undefined and we won't write test cases [outside of the intersection of the intersection of XSD *AND* SQL]"
> > ]]
> > I created a post LC version of the document:
> >  http://www.w3.org/2001/sw/rdb2rdf/directMapping/LC/Overview
> > and added some text about the derivation and extension of the data mappings in the Direct Graph:
> >  http://www.w3.org/2001/sw/rdb2rdf/directMapping/LC/Overview#minimal-DG
> > 
> > 
> >> Thanks to David for scribing
> >> -- 
> >> All the best, Ashok
> >> 
> > 
> > -- 
> > -ericP
> > 
> 

-- 
-ericP

Received on Tuesday, 11 October 2011 15:01:18 UTC