Doubt in non-deterministic content model

Hi..
 
The following schema is non deterministic since the parser will not
determine whether it should compare the element in the instance document
with 1st element declaration or 2nd element declaration.
 
<?xml version="1.0" encoding="UTF-8"?>

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

    <xs:complexType name="foo">

        <xs:sequence>

                <xs:element name="a" maxOccurs="2"/>

                <xs:element name="a"/>

        </xs:sequence>

    </xs:complexType>

</xs:schema>

For the following schema also same scenario is present. But one of the xml
Parsers is not giving any error. Can any body tell me whether the following
schema is non-deterministic or not? 
Also please tell me in some detail about the non-deterministicity of a
content model.
 
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

<!-- restriction xs:any to a sequence -->

    <xs:complexType name="base">

        <xs:sequence>

                <xs:any namespace="##any"/>

                <xs:sequence>

                    <xs:element name="a" minOccurs="0"/>

                </xs:sequence>

        </xs:sequence>

    </xs:complexType>

    <xs:complexType name="derived">

        <xs:complexContent>

            <xs:restriction base="base">

                <xs:sequence>

                    <xs:element name="a" type="xs:string"/>

                    <xs:element name="a" type="xs:string" minOccurs="0"/>

                </xs:sequence>

            </xs:restriction>

        </xs:complexContent>

    </xs:complexType>

</xs:schema>

 

Thanks and Regards,

Bharath.