From: Peter F. Patel-Schneider ([email protected])
Date: 11/30/01
From: [email protected] Subject: RE: Cutting the Patrician datatype knot Date: Fri, 30 Nov 2001 19:19:43 +0200 > > > > -----Original Message----- > > From: ext Ashok Malhotra [mailto:[email protected]] > > Sent: 29 November, 2001 08:25 > > To: Stickler Patrick (NRC/Tampere); [email protected] > > Cc: [email protected]; [email protected] > > Subject: RE: Cutting the Patrician datatype knot > > > > > > > In the above union "data type", the literal "7" maps to > > > two members of the value space. Therefore, it is not a > > > valid data type. > > > > If you define a union type then such anomalies can arise. > > XML Schema specifies how to resolve them. If a literal can be > > interpreted as a valid literal for more than one of the datatypes > > included in a union, it is assumed to have the datatype of the first > > datatype specified in the union for which it is a legal literal. > > > > You may not think this is an elegant solution but it solves the > > problem. > > But doesn't that then preclude the use of (hide) a subset > of the value space? I.e. whatever the intersection is between > the two (or more) value spaces, only the members of that > intersection belonging to the first data type are "accessible". No, again, see the XML Schema specfication. In short, you can access the hidden subspace in several ways, including using xsi:type. > Well, if that's how the union data type is defined to work, then > it's not technically a problem -- i.e. there really is no actual > ambiguity in the mapping -- but it would still IMO be a very > odd data type ;-) Sure, you may consider it to be odd, but it is a valid data type, and it does cause problems for many of the datatype schemes. > Cheers, > > Patrick peter
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