From: Ashok Malhotra <ashokma@microsoft.com>

Date: Wed, 24 Apr 2002 13:59:21 -0700

Message-ID: <E5B814702B65CB4DA51644580E4853FB01488792@red-msg-12.redmond.corp.microsoft.com>

To: <sandygao@ca.ibm.com>, <www-xml-schema-comments@w3.org>

Date: Wed, 24 Apr 2002 13:59:21 -0700

Message-ID: <E5B814702B65CB4DA51644580E4853FB01488792@red-msg-12.redmond.corp.microsoft.com>

To: <sandygao@ca.ibm.com>, <www-xml-schema-comments@w3.org>

Sandy, see comments inline. All the best, Ashok =========================================================== -----Original Message----- From: sandygao@ca.ibm.com [mailto:sandygao@ca.ibm.com] Sent: Wednesday, April 24, 2002 11:43 AM To: www-xml-schema-comments@w3.org Subject: Questions about "equal" fundamental facet 1. Is it defined on "value spaces", or "types"? In 4.2.1 of the datatype spec: "Every *value space* supports the notion of equality, ...". So it seems that "equal" is defined on "value spaces". Does this imply that two (unconnected) types (with the same value space) can have equal values? For example, hexBinary and base64Binary have the same value space ("the set of finite-length sequences of binary octets"). hexBinary value "00" and base64Binary value "AA==" both represent one byte of value "0". Then are the two values equal? I would say they are equal, if "equal" is defined on value spaces. But 3.11.1 of the structure spec says "Values of differing type can only be equal if one type is derived from the other, and the value is in the value space of both". Here it seems to indicate something different. Is this a contradiction? [AM] Equality is defined on values. The values must be in the same value space. Since derivation by restriction merely narrows the value space a value of a base type may equal a value of a derived (by restriction) type. 2. Does the types have to be related by *restriction* or *union*? If type A restricts "integer" by setting "minInclusive=0", and B restricts "integer" by setting "maxInclusive=10". Now A and B are not related by restriction or union. But I still expect value "5" from both types (values spaces) to be equal. (If they have to be related by *restriction* or *union*, doesn't 3.11.1 of the structure spec need to be modified to be more strict, instead of simply saying "derived from"?) [AM] By restriction. My take on these 2 questions: 1. "equal" should be defined on value spaces, because equal values are equal, no matter how they were lexically represented. [AM] Correct! 2. Types used to generate equal (actual) values don't need to be related. As long as there exist a (primitive) value space to which both values belong, and the two values are equal in that value space, then they are equal. This means hexBinary and base64Binary can generate equal values, so can QName and NOTATION. Further on this, maybe the value space of "float" should (or already is) be a subset of that of "double", so that these types can generate equal values. [AM] I don't know how to tell if two value spaces are subsets of some primitive value space. I only know such a relation exists for types derived by restriction. Thanks, Sandy Gao Software Developer, IBM Canada (1-905) 413-3255 sandygao@ca.ibm.comReceived on Wednesday, 24 April 2002 17:03:17 UTC

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