RE: [xml] Failed schema validation with substitution groups and choice

["Buchcik, Kasimier" <k buchcik 4commerce de>]

Hi, 

Fixed in CVS, xmlschemas.c, revision 1.201.

See http://bugzilla.gnome.org/show_bug.cgi?id=341150

In xmlSchemaBuildContentModelForSubstGroup(),
xmlAutomataNewOnceTrans2() was incorrectly used instead of
xmlAutomataNewTransition2(); seems like a copy&paste bug from
the XML_SCHEMA_TYPE_ALL section in xmlSchemaBuildAContentModel().
The usage of xmlAutomataNewOnceTrans2() restricted the members
of substitution-groups (except the group's head) to the occurence
of 1.

Thanks for the thorough report!

Regards,

Kasimier

> -----Original Message-----
> From: xml-bounces gnome org [mailto:xml-bounces gnome org] On 
> Behalf Of Michael Romer
> 
> 
> 
> Greetings.  While working on an XML based project for work, I 
> ran into the
> following bug with the libxml2 validator.  I've attached a 
> simple test case
> that, when run through xmllint, should reproduce the same results I am
> receiving.
> 
> The problem is as follows.  The supplied libxml2 validator, 
> xmllint, will fail
> to validate the following instance document against the 
> schema specified below
> if you uncomment the line specified in the instance document; 
> however when it
> is commented, the instance document will validate just fine.
> 
> Instance document:
> ------------------
> 
> <?xml version="1.0" encoding="UTF-8"?>
> <TestRoot xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
>           xsi:noNamespaceSchemaLocation="common-schema.xsd">
>     <Events>
>         <TestEvent>Test 1.</TestEvent>
>         <!-- Uncomment the following element to cause 
> libxml's xmllint to
>             fail to validate. -->
>         <!-- <TestEvent>Test 2.</TestEvent> -->
>     </Events>
> </TestRoot>
> 
> 
> 
> Schema to validate against:
> ---------------------------
> 
> <?xml version="1.0" encoding="UTF-8"?>
> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";
>            elementFormDefault="qualified"
>            attributeFormDefault="unqualified">
> 
>     <!-- This is the head of our substitution group for 
> events that have only
>         simple content. -->
>     <xs:element name="SimpleEvent" type="SimpleEventType"/>
> 
>     <!-- All SimpleEvent elements have the required set of 
> attributes -->
>     <xs:complexType name="SimpleEventType">
>         <xs:simpleContent>
>             <xs:extension base="xs:anySimpleType">
>             </xs:extension>
>         </xs:simpleContent>
>     </xs:complexType>
> 
>     <!-- Common members of the SimpleEvent substitution group -->
>     <xs:element name="TestEvent" substitutionGroup="SimpleEvent">
>         <xs:complexType>
>             <xs:simpleContent>
>                 <xs:restriction base="SimpleEventType">
>                     <xs:simpleType>
>                         <xs:restriction base="xs:string"/>
>                     </xs:simpleType>
>                 </xs:restriction>
>             </xs:simpleContent>
>         </xs:complexType>
>     </xs:element>
> 
>     <!-- Root element -->
>     <xs:element name="TestRoot" type="TestRootType"/>
> 
>     <!-- Core data type of an audit trail -->
>     <xs:complexType name="TestRootType">
>         <xs:sequence>
>             <xs:element name="Events">
>                 <xs:complexType>
>                     <xs:choice minOccurs="0" maxOccurs="unbounded">
>                         <xs:element ref="SimpleEvent"/>
>                     </xs:choice>
>                 </xs:complexType>
>             </xs:element>
>         </xs:sequence>
>     </xs:complexType>
> 
> </xs:schema>
> 
> 
> 
> I have done numerous test cases and pinned the problem to be 
> the fact that a
> substitution group is being used inside the choice group 
> element, which is
> specified to appear zero or more times in an instance 
> document.  The key is
> that each choice group contains one SimpleEvent, or any 
> element that can be
> substitutable for SimpleEvent (in this case, TestEvent is 
> declared to be part
> of the SimpleEvent substitution group, so it should work just 
> fine).  In
> essense, any choice group that contains an element that can 
> be substituted by
> another element in the corresponding substitution group, and 
> if the schema
> allows for that choice group to appear multiple times in an 
> instance document,
> then the validator will fail to validate any instance 
> document that has more
> than substitutable element specified (as in the above case 
> when the second
> SimpleElement is uncommented from the instance document).
> 
> >From what I can gather, the libxml2 validator is getting 
> confused and instead of
> thinking that the two TestEvent elements in the original 
> instance document
> belong to two separate choice groups, it actually thinks that 
> they are both in
> the same choice group.  If this is true, this would explain 
> the error message
> that is obtained when I run xmllint:
> 
> "element TestEvent: Schemas validity error : Element 
> 'TestEvent': This element
> is not expected."
> 
> I have tried changing the choice group to a sequence group, 
> and the exact same
> error occurs.  I have also used the following validators, and 
> they all will
> validate the supplied instance document against the supplied 
> schema without any
> problem: Xerces, MSXML 4.0 SP2, MSXML.NET, and XSV, hence 
> leading me to believe
> this is truly a bug with the libxml2 validator.
> 
> I've also filled out a Bugzilla bug report describing what 
> has been described in
> this post.
> 
> Thanks,
> Michael Romer
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