Ambiguous Content Models

Hi,

Our users want a virtually wide open content model. However, there are 
the occasional exceptions..
Here is an example:

<xs:sequence minOccurs="1">
    <xs:sequence maxOccurs="unbounded">
        <xs:group ref="tns:GenericElements" minOccurs="0"/>
        <xs:element name="Person" type="tns:Person" minOccurs="0"/>
        <xs:element name="Location" type="tns:Loc" minOccurs="0"/>
    </xs:sequence>
    <xs:element name="Person" type="tns:Person"/>
    <xs:sequence maxOccurs="unbounded">
        <xs:group ref="tns:GenericElements" minOccurs="0"/>
        <xs:element name="Person" type="tns:Person" minOccurs="0"/>
        <xs:element name="Location" type="tns:Loc" minOccurs="0"/>
    </xs:sequence>
</xs:sequence>

In short, they want any element of the three elements in any order, as 
many or as few times as they want. However, they also want at least one 
person element to be present every time.
I think that the above is absolutely valid. However, the IBM Schema 
Quality Checker grumbles about amiguous content models with this.
I am on a new machine, so as yet have not been able to validate samples 
against this model using xerces etc.

Does anybody have any comments on the validity of the above? 

thanks

Max