question about group circle definition

Hi All, 

 

I meet a case in w3c test suite: 

 

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">

 

    <xsd:complexType name="a">

        <xsd:sequence>

            <xsd:group ref="ul" minOccurs="0" maxOccurs="unbounded"/> 

        </xsd:sequence>

    </xsd:complexType> 

 

    <xsd:group name="ul">

        <xsd:sequence>

            <xsd:element name="ul">

                <xsd:complexType>

                    <xsd:sequence>

                        <xsd:choice minOccurs="0" maxOccurs="unbounded">

                            <xsd:element name="li" /> 

                            <xsd:group ref="ul" minOccurs="0" maxOccurs="unbounded" /> 

                        </xsd:choice>

                    </xsd:sequence>

                </xsd:complexType>

            </xsd:element>

        </xsd:sequence>

    </xsd:group>

 

</xsd:schema>

 

I think this case voilate:

3.8.6 Constraints on Model Group Schema Components

All model groups (see Model Groups (¡ì3.8)) must satisfy the following

constraints.

 

Schema Component Constraint: Model Group Correct

All of the following must be true:

2 Circular groups are disallowed. That is, within the {particles} of a group

there must not be at any depth a particle whose {term} is the group itself.

 

However, many schema validators say it is a valid case. 

Somebody knows the reason? 

 

Thanks, 

- Wang Zhuo    

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