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Re: Beginner's Question - Schema Validation Problem

From: <noah_mendelsohn@us.ibm.com>
Date: Wed, 7 Apr 2004 11:21:00 -0400
To: "Ayman El-Geneidy" <aelgeneidy@insightbb.com>
Cc: xmlschema-dev@w3.org
Message-ID: <OFBD54FF45.4353D7D9-ON85256E6F.005388B2@lotus.com>

It would be helpful to see a bit more of your schema.  Presuming that:

<xsd:element name="qos" maxOccurs="1">

is indeed an immediate child (not grandchild) of <xsd:schema>, then your 
schema is not correctly formed.  There are roughly two forms of the 
<xsd:element> construction, plus a common shorthand that puts them 

        <!-- global element declaration: maxoccurs not allowed here -->
        <xsd:element name="x">
                ...definition of "x"..

This defines x, but doesn't use it.  Now let's use it:

        <!-- global element declaration: maxoccurs not allowed here -->
        <xsd:element name="x">
                ...definition of "x"..

        <xsd:complexType name="t">
                <!-- use of element, maxOccurs allowed -->
                <xsd:element ref="x" maxOccurs="3">
        </xsd:complexType name="t">

There is a very common shorthand the defines an element and uses it all in 
one step.  The result is a so-called locally scoped element, that is 
usable only right where you define it (more or less).

        <!-- maxoccurs not allowed here -->
        <xsd:element name="x">
                <xsd:complexType name="t">
                        <xsd:element name="myLocal" maxOccurs="3">
                                ...definition of myLocal...
                </xsd:complexType name="t">

In the above, myLocal is both defined and used.  In this case, you can 
supply maxOccurs, >>because that is controlling the use<<.  It makes no 
sense to have maxOccurs on a global declaration as in your example.   A 
properly written schema processor should have rejected your element 
declaration as illegal for that reason.  It's possible that, seeing 
maxOccurs, the processor went into the part of the logic for dealing with 
element uses and said "ok, where's the definition".  In fact, it's not 
legal or sensible to have a use as an immediate child of <xsd:schema>.   I 
hope I've understood your problem, and that this helps.

Another common source of such problems is misuse of namespaces, but I 
don't see such errors in your example.

Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142

"Ayman El-Geneidy" <aelgeneidy@insightbb.com>
Sent by: xmlschema-dev-request@w3.org
04/07/04 10:15 AM

        To:     <xmlschema-dev@w3.org>
        cc:     (bcc: Noah Mendelsohn/Cambridge/IBM)
        Subject:        Beginner's Question - Schema Validation Problem

I am trying to validate a schema and getting the error "Element 'qos' is 
used but not declared in DTD/Schema". 'qos' is my root element. I have 
looked at several books and at similar messages on this list with no luck.
This is how I am declaring it in my XML file:
And this is how it is declared in the schema file ('qos.xsd' located at 
the same directory as the XML file):
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
     <xsd:element name="qos" maxOccurs="1">
               <xsd:element ref="performance" minOccurs="0" 
           <xsd:element ref="information" minOccurs="0" maxOccurs="1"/>
           <xsd:element ref="configuration" minOccurs="0" maxOccurs="1"/>
           <xsd:element ref="security" minOccurs="0" maxOccurs="1"/> 
      <xsd:attribute ref="service_key" use="required"/>
I have tried qualifying the path of the xsd file as it was explained in a 
previous message and got the same result. I am using the XRay editor from 
I would appreciate any help and guidance.
Thank you.
Received on Wednesday, 7 April 2004 11:22:41 UTC

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