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Re: ambiguous content model - yea or nay?

From: Morris Matsa <mmatsa@us.ibm.com>
Date: Tue, 11 Feb 2003 15:52:09 -0500
To: "Paul Kiel" <paul@hr-xml.org>
Cc: <xmlschema-dev@w3.org>
Message-ID: <OF89A8DD1E.4D2075C8-ON85256CCA.0071DADB@pok.ibm.com>



I believe that it is an ambiguous content model, and it is a legal schema
component.

To see that it is ambiguous, consider the instance: (assume dates are
legal)
<element>
 <AvailabilityStartDate>date1</AvailabilityStartDate>
 <AvailabilityEndDate>date2</AvailabilityEndDate>
</element>

Which list of sequences did you mean?  It could be:
{{date1, date2}}, or {{date1}, {date2}}, or {{}, {}, {}, {date1}, {},
{date2}}, etc.

Thus it is an ambiguous content model.

It is a legal schema component because looking at each tag it is either
"Start" or "End" and you immediately and unambiguously know which particle
in the schema to validate against.  It's the "Unique _Particle_ Attribution
Constraint".


"Paul Kiel" <paul@hr-xml.org>@w3.org on 02/11/2003 02:36:39 PM

Sent by:    xmlschema-dev-request@w3.org


To:    <xmlschema-dev@w3.org>
cc:
Subject:    ambiguous content model - yea or nay?





Question all,

I am getting an "ambiguous content model" error when validating an instance
conforming to this schema:
<xsd:complexType>
     <xsd:sequence maxOccurs="unbounded">
          <xsd:element  name="AvailabilityStartDate" type
="AnyDateTimeNkType" minOccurs="0"/>
          <xsd:element  name="AvailabilityEndDate" type="AnyDateTimeNkType"
minOccurs="0"/>
     </xsd:sequence>
</xsd:complexType>

I only get the error from 1 of 5 parsers/tools that I validate  against.
And only when validating the instance (the schema validates just  fine with
that same tool).

The more I looked at it, the more it seemed "technically" true but I wasn't
sure.

(For the record, this is a bug fix - I plan on eliminating the maxOccurs
attribute on the sequence.)

Curiously,

Paul Kiel
HR-XML Consortium
Received on Tuesday, 11 February 2003 15:53:29 GMT

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