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Extension and Restriction of Wildcard Attribute

From: Asir S Vedamuthu <asirv@webmethods.com>
Date: Fri, 8 Dec 2000 10:19:51 -0500
To: "Www-Xml-Schema-Comments@W3. Org" <www-xml-schema-comments@w3.org>
Cc: "W3c-Xml-Schema-Ig" <w3c-xml-schema-ig@w3.org>, "Ningang chen" <nchen@webmethods.com>
Message-ID: <NEBBIAMHOMNDLFMEIEBAAEILCDAA.asirv@webmethods.com>
First, I would like to observe that extension of wildcard attribute is not
the same as restriction of wildcard attribute. And, these two items are
clearly under specified in the structures draft.

In the structures draft, both extension and restriction of wild card
attribute is described using an arbitrary intensional ( or in tensional :-/,
Microsoft spell check accepts the latter) intersection [1]. Nothing is
specified in the context, extension or restriction. This is quite confusing
(or you are in the middle of no where) if you attempt to map a complex type
surface syntax to components [2].

For discussion, I use two complex types A and B. B is derived from A. These
two types have wild card attributes in the surface syntax.

[Case 1] B extends A. Spec says that the resulting wild card attribute of B
is the arbitrary
intersection of wild card attribute of A and B (found in surface syntax).
This is incorrect. Intuitively, resulting wild card attribute is the union
of wild card attribute of A and B.

[Case 2] B restricts A. Spec says that the resulting wild card attribute of
B is the atria intersection of wild card attribute of A and B (found in
surface syntax). This is incorrect. Intuitively, resulting wild card
attribute is the intersection of wild card attribute of A and B iff,

Wild Card Attribute of [A] intersection [B] = Wild Card Attribute of [B]. If
not it is an error 'cos B is stepping outside the space of A.


Proposed resolutions
(a) Clearly specify what does extension or restriction of wild card
attribute mean?
(b) If extension, it is the union of wild card attribute of A and B
(c) If restriction, it is the intersection of wild card attribute of A and
B, iff the result is the wild card attribute of B

[1] http://www.w3.org/TR/2000/CR-xmlschema-1-20001024/#cos-aw-intersect
[2] http://www.w3.org/TR/2000/CR-xmlschema-1-20001024/#declare-type


Regards, Asir S Vedamuthu
webMethods, USA
Received on Friday, 8 December 2000 10:20:27 GMT

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