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Subject: CAP Normative Schema is improperly defined
- From: "Bob Wyman" <bob@wyman.us>
- To: <emergency-comment@lists.oasis-open.org>
- Date: Sun, 28 Mar 2004 15:49:42 -0500
Title: Message
The normative XML
Schema in the CAP specification is improperly defined and will either generate
validation errors or be rewritten to a form which conforms to XML Schema
when input to common XML Schema processing tools. A major
source of the problems is the fact that what should be anonymous simple types in
the CAP schema are encoded with "name" attributes and are thus not anonymous.
For instance, the CAP schema defines the element msgType as:
<element name =
"msgType">
<simpleType name = "msgType"
>
<restriction base =
"string">
...
</restriction>
</simpleType>
</element>
A proper definition
of the msgType element would *not* include the "name" attribute in the
"simpleType" element. Thus, the proper definition would be:
<element name =
"msgType">
<simpleType>
<restriction
base = "string">
...
</restriction>
</simpleType>
</element>
This improper use of XML Schema occurs at least 10
times in the CAP schema (I may have missed a
couple...)
Given that most well written XML Schema processors will
rewrite or reject the normative CAP schema, it is hard to understand the
justification for proposing a standard that contains a flawed normative
definition. In this case, for interoperability to be had, it is necessary to
assume that all XML Schema processors will either ignore or rewrite the
offending elements of the schema in a consistent manner. While this appears to
be the case so far, it introduces a risk of interpretation that is not
appropriate for a standard such as CAP. For a standard such as CAP, it must be
recognized that misinterpretations of CAP messages can lead to life-or-death
consequences. Such a standard should only be accepted if it has achieved
the highest possible levels of clarity and
quality.
bob wyman
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