Referencing XSD's correctly in XML

[Lord1e]

I'm just seetting out on a quest to get to grips with XML and have already got well and truly confused.

I'm trying to refernce this xml search file >

<?xml version="1.0" encoding="ISO-8859-1"?>

<xsd:schema xmlns:xsd="

http://www.w3.org/2001/XMLSchema"

targetNamespace="schema url in here?"
xmlns="schema url in here?"
elementFormDefault="qualified">
<xsd:include schemaLocation="search_order.xsd"/>
<xsd:element name="search_order">
<xsd:complexType>
<OrderRequest>
<SPReference>###</SPReference>
<RequestType>search_order</RequestType>
<GatewayOrderReferenceList>
<GatewayOrderReferenceList SearchType="detail"> </GatewayOrderReferenceList>
<GatewayOrderReferenceList SearchType="summary"> </GatewayOrderReferenceList>
</GatewayOrderReferenceList>
</OrderRequest>
</xsd:complexType>
</xsd:element>
</xsd:schema>


with this pre built schema >

<?xml version="1.0" encoding="ISO-8859-1"?>
<!-- edited with XMLSpy v2005 U (

http://www.xmlspy.com)

by CB (-) -->
<xs:schema xmlns:xs="

http://www.w3.org/2001/XMLSchema"

elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:element name="OrderRequest">
<xs:annotation>
<xs:documentation>XML Request for a detailed search on individual SPG Order Codes </xs:documentation>
</xs:annotation>
<xs:complexType>
<xs:sequence>
<xs:element name="SPReference" type="xs:string"/>
<xs:element name="RequestType">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="Search_Order"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
<xs:element name="GatewayOrderReferenceList">
<xs:complexType>
<xs:sequence>
<xs:element name="GatewayOrderReference" maxOccurs="unbounded">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:string">
<xs:attribute name="SearchType" use="required">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="Detail"/>
<xs:enumeration value="Summary"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>

I've got errors all over the place and i'm getting very confused.

Could someone point me in the right direction ?