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ACTION-172: Develop list of possible conflicts between XML Schema datatypes and OWL datatypes

From: Achille Fokoue <achille@us.ibm.com>
Date: Wed, 17 Sep 2008 10:19:36 -0400
To: public-owl-wg Group WG <public-owl-wg@w3.org>
Message-ID: <OFCD94F3E2.99F58D71-ON852574C7.004D9E14-852574C7.004EB395@us.ibm.com>
Hi all,

The current version of OWL Syntax Spec already explicitly identifies the 
main differences and conflicts between OWL datatypes and XML Schema 
datatypes [1].  However, the following two minor differences are not 
explicitly mentioned:
1.      In OWL 2, NaN is not equal to itself; whereas xsd:double(NaN) 
(resp. xsd:float(NaN)) is equal to itself according to XML Schema Spec 
[1].  XML Schema Spec states, in the definition of double in section 
3.2.5, that "NaN equals itself but is incomparable with (neither greater 
than nor less than) any other value in the value space".
2.      In OWL 2, the lexical representation of owl:dateTime does not rule 
out year 0 (i.e. '0000-12-31T23:59:59-05:00' is a valid owl:dateTime). XML 
Schema Spec [1] explicitly disallows year 0. This is more likely an 
omission in OWL 2 than a legitimate departure from XML Schema.

The other differences already identified in the current Syntax Spec are as 
follows:
1.      owl:realPlus and owl:real are two new datatypes. They are abstract 
in the sense that  they only define a value space: no literals of the form 
'xxx'^^^owl:realPlus or 'xxx'^^^owl:real are allowed.
2.      The value spaces of xsd:float, xsd:double and xsd:decimal are 
mutually disjoint in XML Schema, but they are not in OWL 2.  In OWL 2, the 
value space of these three types are subset of the value space of 
owl:realPlus
3.      The special value '-0' does not belong to the value space of 
xsd:double and xsd:float defined in XML Schema.
4.      In XML Schema,  the lexical values  of the xsd:double (resp. 
xsd:float) literals '-0' and '0' are both mapped to the same value '0' in 
the double (resp. float)  value space; whereas, in OWL 2, they are mapped 
to two distinct values '-0' and '0'


Best regards,
Achille.

[1] XML Schema Spec Part 2: http://www.w3.org/TR/xmlschema-2/
Received on Wednesday, 17 September 2008 14:20:19 UTC

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