Restricting an elements that has been extended in XSD - xsd

Question

I am trying to create reusable element declarations for a web service to insert and update. I have the following declarations:
<xs:complexType name="commonEntity">
<xs:sequence>
<xs:element name="id" type="snt-common:id" minOccurs="0"
maxOccurs="1" />
<xs:element name="createdByID" type="snt-common:id"
minOccurs="0" maxOccurs="1" />
<xs:element name="createDate" type="snt-common:dateTime"
minOccurs="0" maxOccurs="1" />
<xs:element name="modifiedByID" type="snt-common:id"
minOccurs="0" maxOccurs="1" />
<xs:element name="modifyDate" type="snt-common:dateTime"
minOccurs="0" maxOccurs="1" />
</xs:sequence>
</xs:complexType>
<xs:complexType name="contact">
<xs:complexContent>
<xs:extension base="snt-common:commonEntity">
<xs:sequence>
<xs:element name="firstName" type="snt-common:string255"
minOccurs="0" maxOccurs="1" />
<xs:element name="lastName" type="snt-common:string255"
minOccurs="0" maxOccurs="1" />
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:element id="update" name="ContactUpdateRequest">
<xs:complexType>
<xs:complexContent>
<xs:restriction base="snt:contact">
<xs:sequence>
<xs:element name="id" type="snt-common:id" minOccurs="1"
maxOccurs="1" />
<xs:element name="modifyDate" type="snt-common:dateTime"
minOccurs="1" maxOccurs="1" />
<xs:element name="firstName" type="snt-common:string255"
minOccurs="0" maxOccurs="1" />
<xs:element name="lastName" type="snt-common:string255"
minOccurs="1" maxOccurs="1" />
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
</xs:element>
<xs:element id="insert" name="ContactInsertRequest">
<xs:complexType>
<xs:complexContent>
<xs:restriction base="snt:contact">
<xs:sequence>
<xs:element name="firstName" type="snt-common:string255"
minOccurs="0" maxOccurs="1" />
<xs:element name="lastName" type="snt-common:string255"
minOccurs="1" maxOccurs="1" />
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
</xs:element>
What I am trying to achieve is to create an insert and an update request, both of which are restrictions of contact. Contact in turn is an extension of commonEntity, which is used for all schemas as a base.
Insert works fine since there are no additional restrictions, but for update we require the id and modifyDate (this is how we enforce versioning) in the request. However, I get the following error when validating the schema:
Error for type '#AnonType_ContactUpdateRequest'. The particle of the type is not a valid restriction of the particle of
the base.
It seems as though I cannot restrict elements in the base element, commonEntity. I have tried reordering without success. Is this a nuance of XSD or am I missing something?
Update:
common.xsd
<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:jaxb="http://java.sun.com/xml/ns/jaxb" targetNamespace="http://predictivesolutions.com/schema/common"
xmlns:snt-common="http://predictivesolutions.com/schema/common"
xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
jaxb:extensionBindingPrefixes="xjc" elementFormDefault="qualified"
jaxb:version="2.0">
<xs:annotation>
<xs:appinfo>
<jaxb:globalBindings>
<xjc:javaType name="java.util.Calendar" xmlType="xs:dateTime"
adapter="com.ps.snt.ws.util.CalendarDateTimeAdapter" />
<xjc:javaType name="java.util.Calendar" xmlType="xs:date"
adapter="com.ps.snt.ws.util.CalendarDateAdapter" />
</jaxb:globalBindings>
</xs:appinfo>
</xs:annotation>
<!-- Creating this id type to use in the event we need to change to a long,
we can just do it here. -->
<xs:simpleType name="id">
<xs:restriction base="xs:integer">
<xs:minInclusive value="1"></xs:minInclusive>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="dateTime">
<xs:restriction base="xs:dateTime">
<!-- 2013-11-06T11:17:17.043-05:00 -->
<xs:pattern value="\d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d.\d\d\d[+\-]\d\d:\d\d" />
<!-- 2013-11-06T11:17:17-05:00 -->
<xs:pattern value="\d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d[+\-]\d\d:\d\d" />
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="string255">
<xs:restriction base="xs:string">
<xs:maxLength value="255" />
</xs:restriction>
</xs:simpleType>
<xs:complexType name="commonEntity">
<xs:sequence>
<xs:element name="id" type="snt-common:id" minOccurs="0"
maxOccurs="1" />
<xs:element name="createdByID" type="snt-common:id"
minOccurs="0" maxOccurs="1" />
<xs:element name="createDate" type="snt-common:dateTime"
minOccurs="0" maxOccurs="1" />
<xs:element name="modifiedByID" type="snt-common:id"
minOccurs="0" maxOccurs="1" />
<xs:element name="modifyDate" type="snt-common:dateTime"
minOccurs="0" maxOccurs="1" />
</xs:sequence>
</xs:complexType>
</xs:schema>
contact.xsd
<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://predictivesolutions.com/schema/v1_1" xmlns:snt="http://predictivesolutions.com/schema/v1_1"
xmlns:snt-common="http://predictivesolutions.com/schema/common"
elementFormDefault="qualified">
<xs:import namespace="http://predictivesolutions.com/schema/common"
schemaLocation="../common.xsd" />
<xs:complexType name="contact">
<xs:complexContent>
<xs:extension base="snt-common:commonEntity">
<xs:sequence>
<xs:element name="firstName" type="snt-common:string255"
minOccurs="0" maxOccurs="1" />
<xs:element name="lastName" type="snt-common:string255"
minOccurs="0" maxOccurs="1" />
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<!-- For transporting data -->
<xs:element id="contact" name="contact" type="snt:contact">
</xs:element>
</xs:schema>
ContactService.xsd
<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://predictivesolutions.com/schema/v1_1" xmlns:snt="http://predictivesolutions.com/schema/v1_1"
xmlns:snt-common="http://predictivesolutions.com/schema/common"
elementFormDefault="qualified">
<xs:import namespace="http://predictivesolutions.com/schema/common"
schemaLocation="../common.xsd" />
<xs:include schemaLocation="contact.xsd" />
<!-- Request/Response for inserting data -->
<xs:element id="insert" name="ContactInsertRequest">
<xs:complexType>
<xs:complexContent>
<xs:restriction base="snt:contact">
<xs:sequence>
<xs:element name="firstName" type="snt-common:string255"
minOccurs="0" maxOccurs="1" />
<xs:element name="lastName" type="snt-common:string255"
minOccurs="1" maxOccurs="1" />
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
</xs:element>
<!-- Request/Response for updating data -->
<xs:element id="update" name="ContactUpdateRequest">
<xs:complexType>
<xs:complexContent>
<xs:restriction base="snt:contact">
<xs:sequence>
<xs:element name="id" type="snt-common:id" minOccurs="1"
maxOccurs="1" />
<xs:element name="modifyDate" type="snt-common:dateTime"
minOccurs="1" maxOccurs="1" />
<xs:element name="firstName" type="snt-common:string255"
minOccurs="0" maxOccurs="1" />
<xs:element name="lastName" type="snt-common:string255"
minOccurs="1" maxOccurs="1" />
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
</xs:element>
</xs:schema>