Co-occurrence Constraints

[Eric W. Sirko]

Hi,

Eric van der Vlist's book XML Schema says that we can use xs:key to declare
co-occurrence constraints. The example he uses (boiled down a bit) is a
"book" element that must have either an "isbn" attribute or an "isbn" child
element, but not both:

<?xml version="1.0" encoding="utf-8" ?>
<xs:schema targetNamespace="http://www.example.com"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns="http://www.example.com"
elementFormDefault="qualified">

<xs:element name="book">
<xs:complexType>
<xs:sequence>
<xs:element name="isbn" type="xs:string" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="isbn" type="xs:string"/>
</xs:complexType>

<xs:key name="dummy">
<xs:selector xpath="."/>
<xs:field xpath="isbn|@isbn"/>
</xs:key>

</xs:element>

</xs:schema>

Now, if the isbn attribute (only) is present, it validates fine. But if the
isbn child (only) is present, I get the following validation error:

The identity constraint 'http://www.example.com:dummy' validation has failed
due to either a key is missing or the exsisting key has an empty node.

And if both the attribute and child are present, I get no validation error
(which is wrong).

I am using Visual Studio .NET, hence the .NET Framework version 1.0. Am I
experiencing a limitation in Microsoft's support for XML Schema, or am I
missing something? Any insights appreciated!
Eric W. Sirko

[Priscilla Walmsley]

Hi Eric,

XPath expressions like (isbn|@isbn) are not affected by default namespace
declarations. Therefore, you must assign a prefix to the target namespace
and use that prefix in the XPath expression, or it won't find the isbn
element. So, it should look like this:

<?xml version="1.0" encoding="utf-8" ?>
<xs:schema targetNamespace="http://www.example.com"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:ex="http://www.example.com"
elementFormDefault="qualified">

<xs:element name="book">
<xs:complexType>
<xs:sequence>
<xs:element name="isbn" type="xs:string" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="isbn" type="xs:string"/>
</xs:complexType>

<xs:key name="dummy">
<xs:selector xpath="."/>
<xs:field xpath="ex:isbn|@isbn"/>
</xs:key>

</xs:element>

</xs:schema>

Hope that helps,
Priscilla
------------------------------------------------------------------
Priscilla Walmsley
Author, Definitive XML Schema / XML in Office 2003
http://www.datypic.com
------------------------------------------------------------------

"Eric W. Sirko" <es****@sw-sol.com> wrote in message
news:ed*************@TK2MSFTNGP12.phx.gbl...

Hi,

Eric van der Vlist's book XML Schema says that we can use xs:key to
declare
co-occurrence constraints. The example he uses (boiled down a bit) is a
"book" element that must have either an "isbn" attribute or an "isbn"
child
element, but not both:

<?xml version="1.0" encoding="utf-8" ?>
<xs:schema targetNamespace="http://www.example.com"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns="http://www.example.com"
elementFormDefault="qualified">

<xs:element name="book">
<xs:complexType>
<xs:sequence>
<xs:element name="isbn" type="xs:string" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="isbn" type="xs:string"/>
</xs:complexType>

<xs:key name="dummy">
<xs:selector xpath="."/>
<xs:field xpath="isbn|@isbn"/>
</xs:key>

</xs:element>

</xs:schema>

Now, if the isbn attribute (only) is present, it validates fine. But if
the
isbn child (only) is present, I get the following validation error:

The identity constraint 'http://www.example.com:dummy' validation has
failed
due to either a key is missing or the exsisting key has an empty node.

And if both the attribute and child are present, I get no validation error
(which is wrong).

I am using Visual Studio .NET, hence the .NET Framework version 1.0. Am I
experiencing a limitation in Microsoft's support for XML Schema, or am I
missing something? Any insights appreciated!
Eric W. Sirko

[Eric W. Sirko]

Thanks, that makes sense. But it makes no difference (well, maybe it's
different, but it still doesn't work properly). The Microsoft validating
parser just blows, I guess..

Eric
"Priscilla Walmsley" <no****@datypic.com> wrote in message
news:#h**************@TK2MSFTNGP11.phx.gbl...

Hi Eric,

XPath expressions like (isbn|@isbn) are not affected by default namespace
declarations. Therefore, you must assign a prefix to the target namespace
and use that prefix in the XPath expression, or it won't find the isbn
element. So, it should look like this:

<?xml version="1.0" encoding="utf-8" ?>
<xs:schema targetNamespace="http://www.example.com"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:ex="http://www.example.com"
elementFormDefault="qualified">

<xs:element name="book">
<xs:complexType>
<xs:sequence>
<xs:element name="isbn" type="xs:string" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="isbn" type="xs:string"/>
</xs:complexType>

<xs:key name="dummy">
<xs:selector xpath="."/>
<xs:field xpath="ex:isbn|@isbn"/>
</xs:key>

</xs:element>

</xs:schema>

Hope that helps,
Priscilla
------------------------------------------------------------------
Priscilla Walmsley
Author, Definitive XML Schema / XML in Office 2003
http://www.datypic.com
------------------------------------------------------------------

"Eric W. Sirko" <es****@sw-sol.com> wrote in message
news:ed*************@TK2MSFTNGP12.phx.gbl...

Hi,

Eric van der Vlist's book XML Schema says that we can use xs:key to
declare
co-occurrence constraints. The example he uses (boiled down a bit) is a
"book" element that must have either an "isbn" attribute or an "isbn"
child
element, but not both:

<?xml version="1.0" encoding="utf-8" ?>
<xs:schema targetNamespace="http://www.example.com"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns="http://www.example.com"
elementFormDefault="qualified">

<xs:element name="book">
<xs:complexType>
<xs:sequence>
<xs:element name="isbn" type="xs:string" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="isbn" type="xs:string"/>
</xs:complexType>

<xs:key name="dummy">
<xs:selector xpath="."/>
<xs:field xpath="isbn|@isbn"/>
</xs:key>

</xs:element>

</xs:schema>

Now, if the isbn attribute (only) is present, it validates fine. But if
the
isbn child (only) is present, I get the following validation error:

The identity constraint 'http://www.example.com:dummy' validation has
failed
due to either a key is missing or the exsisting key has an empty node.

And if both the attribute and child are present, I get no validation error (which is wrong).

I am using Visual Studio .NET, hence the .NET Framework version 1.0. Am I experiencing a limitation in Microsoft's support for XML Schema, or am I
missing something? Any insights appreciated!
Eric W. Sirko