George,

I tried your suggestion -- and various other experiments as well.  =
Nothing seems to work as I expect.


EXPERIMENT 1 - NO NESTING, NO EMPHASIS

XSD:
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://www.ubs.com/namespace/wbml-render"
    xmlns:wbr="http://www.ubs.com/namespace/wbml-render"
    xmlns="http://www.ubs.com/namespace/wbml-render" =
elementFormDefault="qualified"
    attributeFormDefault="unqualified">
    <xs:complexType name="footnoteBase" mixed="true">
        <xs:annotation>
            <xs:documentation>The text to which the footnote =
pertains.</xs:documentation>
        </xs:annotation>
    </xs:complexType>
    <xs:complexType name="footnote">
        <xs:annotation>
            <xs:documentation>Composed of base and =
explanation.</xs:documentation>
        </xs:annotation>
        <xs:sequence>
            <xs:element name="footnoteBase" type="footnoteBase"/>
            <xs:element name="footnoteExplanation" type="xs:string" =
minOccurs="0"/>
        </xs:sequence>
        <xs:attribute name="footnoteId" type="xs:NMTOKEN" =
use="optional"/>
        <xs:attribute name="footnoteRef" type="xs:NMTOKEN" =
use="optional"/>
    </xs:complexType>
    <xs:element name="footnote" type="footnote"/>
    <xs:element name="para">
        <xs:complexType mixed="true">
            <xs:sequence>
                <xs:element ref="footnote" minOccurs="0" =
maxOccurs="unbounded"/>
            </xs:sequence>
        </xs:complexType>
        <xs:key name="ref_or_explanation">
            <xs:selector xpath=".//wbr:footnote"/>
            <xs:field xpath="wbr:footnoteExplanation | @footnoteRef"/>
        </xs:key>
    </xs:element>
</xs:schema>

XML:
<?xml version="1.0" encoding="UTF-8"?>
<wbr:para xmlns:wbr="http://www.ubs.com/namespace/wbml-render"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.ubs.com/namespace/wbml-render
    =
file:/Users/richard/Documents/Work/Accessibility/Schemas/test_footnote_no=
Nesting_noEmphasis.xsd"> Now is 
    <wbr:footnote footnoteRef="abc">
        <wbr:footnoteBase>the</wbr:footnoteBase>
        <!--<wbr:footnoteExplanation>As Clinton said, "It depends on =
what you mean by 'the'."</wbr:footnoteExplanation>-->
    </wbr:footnote> for 
    <wbr:footnote>
        <wbr:footnoteBase>the</wbr:footnoteBase>
        <wbr:footnoteExplanation>As Clinton said, "It depends on what =
you mean by 'the'."</wbr:footnoteExplanation>
    </wbr:footnote> for 
    <wbr:footnote>
        <wbr:footnoteBase>the</wbr:footnoteBase>
        <wbr:footnoteExplanation>As Hilary Clinton said, "It depends on =
what he means by 'the'."</wbr:footnoteExplanation>
    </wbr:footnote> for 
</wbr:para>

RESULT: XML is valid.

EXPERIMENT 2 - NO NESTING, EMPHASIS

XSD:
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://www.ubs.com/namespace/wbml-render"
    xmlns:wbr="http://www.ubs.com/namespace/wbml-render"
    xmlns="http://www.ubs.com/namespace/wbml-render" =
elementFormDefault="qualified"
    attributeFormDefault="unqualified">
    <xs:element name="emphasis" type="xs:string"/>
    <xs:complexType name="footnoteExplanationWithEmphasis" =
mixed="true">
        <xs:annotation>
            <xs:documentation>The text explaining the footnote. The =
explanation may have emphasis child elements (think italics or =
bold).</xs:documentation>
        </xs:annotation>
        <xs:sequence>
            <xs:element ref="emphasis" minOccurs="0" =
maxOccurs="unbounded"/>
        </xs:sequence>
        <xs:attribute name="footnoteExplanation" type="xs:NMTOKEN" =
fixed="footnoteExplanation"/>
    </xs:complexType>
    <xs:complexType name="footnoteBase" mixed="true">
        <xs:annotation>
            <xs:documentation>The text to which the footnote =
pertains.</xs:documentation>
        </xs:annotation>
    </xs:complexType>
    <xs:complexType name="footnoteWithEmphasis">
        <xs:annotation>
            <xs:documentation>Composed of base and explanation.  =
Explanation may have emphasis child elements.</xs:documentation>
        </xs:annotation>
        <xs:sequence>
            <xs:element name="footnoteBase" type="footnoteBase"/>
            <xs:element name="footnoteExplanation" =
type="footnoteExplanationWithEmphasis"
                minOccurs="0"/>
        </xs:sequence>
        <xs:attribute name="footnoteId" type="xs:NMTOKEN" =
use="optional"/>
        <xs:attribute name="footnoteRef" type="xs:NMTOKEN" =
use="optional"/>
    </xs:complexType>
    <xs:element name="footnote" type="footnoteWithEmphasis"/>
    <xs:element name="para">
        <xs:complexType mixed="true">
            <xs:sequence>
                <xs:element ref="footnote" minOccurs="0" =
maxOccurs="unbounded"/>
            </xs:sequence>
        </xs:complexType>
        <xs:key name="ref_or_explanation">
            <xs:selector xpath=".//wbr:footnote"/>
            <xs:field =
xpath="wbr:footnoteExplanation/@footnoteExplanation | @footnoteRef"/>
        </xs:key>
    </xs:element>
</xs:schema>

Note the modifications necessary in order to avoid a mix of complex and =
simple type in the xs:field!

The XML of Experiment 1 should validate -- at least, that's my =
intention! -- but it does not.  Xerces (i.e., Oxygen 7) complains that =
the last two elements have duplicate key.  By moving the xs:key into the =
element, I can avoid this error message:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://www.ubs.com/namespace/wbml-render"
    xmlns:wbr="http://www.ubs.com/namespace/wbml-render"
    xmlns="http://www.ubs.com/namespace/wbml-render" =
elementFormDefault="qualified"
    attributeFormDefault="unqualified">
    <xs:element name="emphasis" type="xs:string"/>
    <xs:complexType name="footnoteExplanationWithEmphasis" =
mixed="true">
        <xs:annotation>
            <xs:documentation>The text explaining the footnote. The =
explanation may have emphasis child elements (think italics or =
bold).</xs:documentation>
        </xs:annotation>
        <xs:sequence>
            <xs:element ref="emphasis" minOccurs="0" =
maxOccurs="unbounded"/>
        </xs:sequence>
        <xs:attribute name="footnoteExplanation" type="xs:NMTOKEN" =
fixed="footnoteExplanation"/>
    </xs:complexType>
    <xs:complexType name="footnoteBase" mixed="true">
        <xs:annotation>
            <xs:documentation>The text to which the footnote =
pertains.</xs:documentation>
        </xs:annotation>
    </xs:complexType>
    <xs:complexType name="footnoteWithEmphasis">
        <xs:annotation>
            <xs:documentation>Composed of base and explanation.  =
Explanation may have emphasis child elements.</xs:documentation>
        </xs:annotation>
        <xs:sequence>
            <xs:element name="footnoteBase" type="footnoteBase"/>
            <xs:element name="footnoteExplanation" =
type="footnoteExplanationWithEmphasis"
                minOccurs="0"/>
        </xs:sequence>
        <xs:attribute name="footnoteId" type="xs:NMTOKEN" =
use="optional"/>
        <xs:attribute name="footnoteRef" type="xs:NMTOKEN" =
use="optional"/>
    </xs:complexType>
    <xs:element name="footnote" type="footnoteWithEmphasis">
        <xs:key name="ref_or_explanation">
            <xs:selector xpath="."/>
            <xs:field =
xpath="wbr:footnoteExplanation/@footnoteExplanation | @footnoteRef"/>
        </xs:key>
    </xs:element>
    <xs:element name="para">
        <xs:complexType mixed="true">
            <xs:sequence>
                <xs:element ref="footnote" minOccurs="0" =
maxOccurs="unbounded"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>

XML:
<?xml version="1.0" encoding="UTF-8"?>
<wbr:para xmlns:wbr="http://www.ubs.com/namespace/wbml-render"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.ubs.com/namespace/wbml-render
    =
file:/Users/richard/Documents/Work/Accessibility/Schemas/test_footnote_no=
Nesting_Emphasis.xsd"> Now is 
    <wbr:footnote footnoteRef="abc">
        <wbr:footnoteBase>the</wbr:footnoteBase>
        <!--<wbr:footnoteExplanation>As Clinton said, "It depends on =
what you mean by 'the'."</wbr:footnoteExplanation>-->
    </wbr:footnote> for 
    <wbr:footnote>
        <wbr:footnoteBase>the</wbr:footnoteBase>
        <wbr:footnoteExplanation>As Clinton said, "It depends on what =
you mean by =
'<wbr:emphasis>the</wbr:emphasis>'."</wbr:footnoteExplanation>
    </wbr:footnote> for 
    <wbr:footnote>
        <wbr:footnoteBase>the</wbr:footnoteBase>
        <wbr:footnoteExplanation>As <wbr:emphasis>Hilary =
Clinton</wbr:emphasis> said, "It depends on what he means by =
'the'."</wbr:footnoteExplanation>
    </wbr:footnote> for 
</wbr:para>

This has emphasis elements and validates.

EXPERIMENT 3 - NESTING, EMPHASIS

XSD:
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://www.ubs.com/namespace/wbml-render"
    xmlns:wbr="http://www.ubs.com/namespace/wbml-render"
    xmlns="http://www.ubs.com/namespace/wbml-render" =
elementFormDefault="qualified"
    attributeFormDefault="unqualified">
    <xs:element name="emphasis" type="xs:string"/>
    <xs:complexType name="footnoteExplanationWithEmphasis" =
mixed="true">
        <xs:annotation>
            <xs:documentation>The text explaining the footnote. The =
explanation may have emphasis child elements (think italics or =
bold).</xs:documentation>
        </xs:annotation>
        <xs:sequence>
            <xs:element ref="emphasis" minOccurs="0" =
maxOccurs="unbounded"/>
        </xs:sequence>
        <xs:attribute name="footnoteExplanation" type="xs:NMTOKEN" =
fixed="footnoteExplanation"/>
    </xs:complexType>
    <xs:complexType name="footnoteBase" mixed="true">
        <xs:annotation>
            <xs:documentation>The text to which the footnote =
pertains.</xs:documentation>
        </xs:annotation>
    </xs:complexType>
    <xs:complexType name="footnoteWithEmphasis">
        <xs:annotation>
            <xs:documentation>Composed of base and explanation.  =
Explanation may have emphasis child elements.</xs:documentation>
        </xs:annotation>
        <xs:sequence>
            <xs:element name="footnoteBase" type="footnoteBase"/>
            <xs:element name="footnoteExplanation" =
type="footnoteExplanationWithEmphasis"
                minOccurs="0"/>
        </xs:sequence>
        <xs:attribute name="footnoteId" type="xs:NMTOKEN" =
use="optional"/>
        <xs:attribute name="footnoteRef" type="xs:NMTOKEN" =
use="optional"/>
    </xs:complexType>
    <xs:element name="footnote" type="footnoteWithEmphasis">
        <xs:key name="ref_or_explanation">
            <xs:selector xpath="."/>
            <xs:field =
xpath="wbr:footnoteExplanation/@footnoteExplanation | @footnoteRef"/>
        </xs:key>
    </xs:element>
    <xs:element name="para">
        <xs:complexType mixed="true">
            <xs:sequence>
                <xs:element ref="footnote" minOccurs="0" =
maxOccurs="unbounded"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>

XML:
<?xml version="1.0" encoding="UTF-8"?>
<wbr:para xmlns:wbr="http://www.ubs.com/namespace/wbml-render"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.ubs.com/namespace/wbml-render
    =
file:/Users/richard/Documents/Work/Accessibility/Schemas/test_footnote_Ne=
sting_Emphasis.xsd"> Now is 
    <wbr:footnote footnoteRef="abc">
        <wbr:footnoteBase>the</wbr:footnoteBase>
        <!--<wbr:footnoteExplanation>As Clinton said, "It depends on =
what you mean by 'the'."</wbr:footnoteExplanation>-->
    </wbr:footnote> for 
    <wbr:footnote>
        <wbr:footnoteBase>the</wbr:footnoteBase>
        <wbr:footnoteExplanation>As Clinton said, "It depends on what =
you mean by =
'<wbr:emphasis>the</wbr:emphasis>'."</wbr:footnoteExplanation>
    </wbr:footnote> for 
    <wbr:footnote>
        <wbr:footnoteBase>the</wbr:footnoteBase>
        <wbr:footnoteExplanation>As <wbr:emphasis>Hilary =
Clinton</wbr:emphasis> said, "It depends on what he means by =
'the'."</wbr:footnoteExplanation>
    </wbr:footnote> for 
    <wbr:footnote>
        <wbr:footnoteBase>
            <wbr:footnote>
                <wbr:footnoteBase>
                    <wbr:footnote footnoteRef="x22">
                        <wbr:footnoteBase>all</wbr:footnoteBase>
                    </wbr:footnote> good
                </wbr:footnoteBase>
                <wbr:footnoteExplanation>In some inner =
sense.</wbr:footnoteExplanation>
            </wbr:footnote> men
        </wbr:footnoteBase>
        <wbr:footnoteExplanation>Good women, =
too.</wbr:footnoteExplanation>
    </wbr:footnote>
</wbr:para>

Of the nested footnotes only the inner-most validates.  For each of the =
containing footnotes Xerces complains that the field matches more than =
one value within the scope of its selector, but that the key has no =
value!  Commenting out the inner-most footnote cause what then becomes =
the inner-most footnote to suddenly become valid; the enclosing footnote =
is still not.

In summary, there seem to be many problems:
1.  As you noted, there is a problem with the order in which the =
particles of the 'or' (|) are specified.
2.  The xs:key must be attached to the footnote, not to an element that =
is sure to be an ancestor of any footnote, if Xerces is to validate even =
unnested footnote.
3.  Even attaching the xs:key to each footnote does not seem to isolate =
them from each other sufficiently to ensure that Xerces validates nested =
footnotes.

Interestingly, LIBXML validate the sample of with nesting and emphasis.

Can you give me some insight into what Xerces might be doing to arrive =
at its conclusion that my XML is invalid?

Thanks,
Richard


-----Original Message-----
From: George Cristian Bina [mailto:george@o...]
Sent: Fri 02/17/06 09:36
To: George Cristian Bina
Cc: Liu, Richard; xmlschema-dev@w...
Subject: Re: xs:key and nesting
 
Looking over the already recorded issues it seems that this is a 
manifestation of the
https://issues.apache.org/jira/browse/XERCESJ-832

A workaround is to replace

<xs:field xpath="wbr:footnoteExplanation | @footnoteRef"/>

with

<xs:field xpath="@footnoteRef | wbr:footnoteExplanation"/>

Best Regards,
George
---------------------------------------------------------------------
George Cristian Bina
<oXygen/> XML Editor, Schema Editor and XSLT Editor/Debugger
www.---.com


George Cristian Bina wrote:
> The problem appears also with the latest SVN snapshot. I will report 
> that on Apache Jira as soon as that will be available, now I get 
> "Service Temporarily Unavailable" when trying to access Apache Jira.
> 
> Best Regards,
> George
> ---------------------------------------------------------------------
> George Cristian Bina
> <oXygen/> XML Editor, Schema Editor and XSLT Editor/Debugger
> www.---.com
> 
> 
> George Cristian Bina wrote:
>> Hi Richard,
>>
>> This looks to me like a bug in Xerces 2.7.1.
>> I will check that against the current Xerces SVN snapshot to see if =
it 
>> shows the same problem and let you know.
>>
>> Best Regards,
>> George
>> ---------------------------------------------------------------------
>> George Cristian Bina
>> <oXygen/> XML Editor, Schema Editor and XSLT Editor/Debugger
>> www.---.com
>>
>>
>> richard.liu@u... wrote:
>>> I have the following schema:
>>>
>>> <?xml version="1.0" encoding="UTF-8"?>
>>> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
>>>     targetNamespace="http://www.ubs.com/namespace/wbml-render"
>>>     xmlns:wbr="http://www.ubs.com/namespace/wbml-render"
>>>     xmlns="http://www.ubs.com/namespace/wbml-render"
>>> elementFormDefault="qualified"
>>>     attributeFormDefault="unqualified">
>>>     <xs:complexType name="footnoteExplanation">
>>>         <xs:annotation>
>>>             <xs:documentation>The text explaining the
>>> footnote.</xs:documentation>
>>>         </xs:annotation>
>>>         <xs:simpleContent>
>>>             <xs:extension base="xs:string"/>
>>>         </xs:simpleContent>
>>>     </xs:complexType>
>>>     <xs:complexType name="footnote">
>>>         <xs:annotation>
>>>             <xs:documentation>Composed of base and
>>> explanation.</xs:documentation>
>>>         </xs:annotation>
>>>         <xs:sequence>
>>>             <xs:element name="footnoteBase" =
type="footnoteBase"/>
>>>             <xs:element name="footnoteExplanation"
>>> type="footnoteExplanation" minOccurs="0"/>
>>>         </xs:sequence>
>>>         <xs:attribute name="footnoteId" type="xs:NMTOKEN"
>>> use="optional"/>
>>>         <xs:attribute name="footnoteRef" type="xs:NMTOKEN"
>>> use="optional"/>
>>>     </xs:complexType>
>>>     <xs:complexType name="footnoteBase" mixed="true">
>>>         <xs:annotation>
>>>             <xs:documentation>The text to which the footnote
>>> pertains.</xs:documentation>
>>>         </xs:annotation>
>>>         <xs:sequence>
>>>             <xs:element ref="footnote" minOccurs="0"
>>> maxOccurs="unbounded"/>
>>>         </xs:sequence>           </xs:complexType>
>>>     <xs:element name="footnote" type="footnote">
>>>         <!--<xs:key name="ref_or_explanation">
>>>             <xs:selector xpath="."/>
>>>             <xs:field xpath="wbr:footnoteExplanation | =
@footnoteRef"/>
>>>         </xs:key>-->
>>>     </xs:element>
>>>     <xs:element name="para">
>>>         <xs:complexType mixed="true">
>>>             <xs:sequence>
>>>                 <xs:element ref="footnote" minOccurs="0"
>>> maxOccurs="unbounded"/>
>>>             </xs:sequence>
>>>         </xs:complexType>
>>>         <xs:key name="ref_or_explanation">
>>>             <xs:selector xpath=".//wbr:footnote"/>
>>>             <xs:field xpath="wbr:footnoteExplanation | =
@footnoteRef"/>
>>>         </xs:key>
>>>     </xs:element>
>>> </xs:schema>
>>>
>>> and the following XML schema instance
>>>
>>> <?xml version="1.0" encoding="UTF-8"?>
>>> <wbr:para xmlns:wbr="http://www.ubs.com/namespace/wbml-render"
>>>     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>>>     xsi:schemaLocation="http://www.ubs.com/namespace/wbml-render
>>>  
>>> =
file:/Users/richard/Documents/Work/Accessibility/Schemas/test_footnote.x
>>> sd"> Now is     <wbr:footnote footnoteRef="abc">
>>>         <wbr:footnoteBase>the</wbr:footnoteBase>
>>>         <!--<wbr:footnoteExplanation>As Clinton said, "It depends on
>>> what you mean by 'the'."</wbr:footnoteExplanation>-->
>>>     </wbr:footnote> for     <wbr:footnote>
>>>         <wbr:footnoteBase>
>>>             <wbr:footnote>
>>>                 <wbr:footnoteBase>
>>>                     <wbr:footnote footnoteRef="x22">
>>>                         <wbr:footnoteBase>all</wbr:footnoteBase>
>>>                     </wbr:footnote> good
>>>                 </wbr:footnoteBase>
>>>                 <wbr:footnoteExplanation>In some inner
>>> sense.</wbr:footnoteExplanation>
>>>             </wbr:footnote> men
>>>         </wbr:footnoteBase>
>>>         <wbr:footnoteExplanation>Good women,
>>> too.</wbr:footnoteExplanation>
>>>     </wbr:footnote>
>>> </wbr:para>
>>>
>>> The xs:key on the para element is supposed to ensure that each =
footnote
>>> descendant has either a footnoteExplanation child or a footnoteRef
>>> attribute.  The first footnote child of para "works" as desired (in
>>> Oxygen 7, i.e., Xerces):  Uncommenting the footnoteExplanation =
element
>>> results in an error, as does deleting the footnoteRef attribute.
>>>
>>> The second footnote element is rather complicated, because the model
>>> permits "nesting" footnotes.  The XML seems valid:  The second =
footnote
>>> element has a footnoteExplanation and no footnoteRef, so does its =
first
>>> footnote descendent, and the innermost footnote has a footnoteRef
>>> attribute and no footnoteExplanation.
>>>
>>> Nevertheless, I receive the following two error messages (I've =
pasted
>>> the offending statement after the Location):
>>>
>>> SystemID:
>>> =
/Users/richard/Documents/Work/Accessibility/Schemas/test_footnote.xml
>>> Location: 18:88
>>>                 <wbr:footnoteExplanation>In some inner
>>> sense.</wbr:footnoteExplanation>
>>> Description: E Identity constraint error:  field
>>> "./wbr:footnoteExplanation|@footnoteRef" matches more than one value
>>> within the scope of its selector; fields must match unique values.
>>>
>>> SystemID:
>>> =
/Users/richard/Documents/Work/Accessibility/Schemas/test_footnote.xml
>>> Location: 21:76
>>>         <wbr:footnoteExplanation>Good women,
>>> too.</wbr:footnoteExplanation>
>>> Description: E Identity constraint error:  field
>>> "./wbr:footnoteExplanation|@footnoteRef" matches more than one value
>>> within the scope of its selector; fields must match unique values.
>>>
>>> Can anybody tell me what I'm missing?
>>>
>>> Thanks,
>>> Richard
>>>


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