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Online validator: '[', ']', and '-' freely accepted in patterns

From: Dave Evans <dme@sirius-software.com>
Date: Tue, 9 Jan 2007 12:28:18 EST
Message-ID: <E1H4Knb-0000SU-5x@aji.w3.org>

Hi, I have tried to use the online schema validator:


I am trying to validate an instance document.  In the "Address(es):"
input area, I have entered two URLs, separated by a space:


I think that this schema should not be accepted, because it contains
a pattern which is not legal according to the recommendation:

        <xs:pattern value="(&#x5B;w-x-&#x5B;y-z&#x5D;|&#x5D;)+"/>

(The pattern is equivalent to  ([w-x-[y-z]|])+ but I have used
character references in case square brackets don't transmit well from
my e-mail to yours.)

In order to parse this pattern, I believe that the final right square
bracket (&#x5D;) must correspond to production [10] for Char, but that
production explicitly excludes left and right square brackets.

Similarly, within the character class, the 2nd hyphen ("-") and
the 2nd left square bracket (&#x5B;) each must correspond to
production [22] for XmlCharIncDash, but that production excludes left
and right square brackets, and furthermore the third bullet item
following the Character Range productions stipulates that a hyphen
can only occur at the start or end of a positive character group,
so the 2nd hyphen should be illegal.

I have asked before about pattern support in the online validator,
and I appreciated your quick feedback, telling me that sometimes an
instance document which is invalid due to a pattern restriction is
erroneously accepted as valid.

In this case, it seems to me that a schema which contains a
syntactically invalid pattern is accepted.

My guess is that you are using a regex engine which does not have
the same syntax nor semantics as pattern restrictions in the XML
Schema Recommendation, resulting in these "falsely valid" schema.

I just wanted to check if that is the case, and would appreciate
any comments you may have.

Thank you again.

        Dave Evans.
        Sirius Software, Inc.
        875 Massachusetts Ave., Suite 21
        Cambridge, MA 02139
        617-876-6677 x204,  fax 617-234-1204
        e-mail:  dme@sirius-software.com
Received on Tuesday, 9 January 2007 17:30:27 UTC

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