No type definition was found

I have a XML file which gives the following error in XMLSpy: Could not validate element 'ik_om_cor:bpm_cancel_order_om'. No type definition was found.

The XML looks like this:

<?xml version="1.0" encoding="ISO-8859-1"?>
<clientsystems xmlns="http://schemaserver/schemas/1.0/" xmlns:ik_om_cor="http://schemaserver/schemas/1.0/ik_om_cor" xmlns:ik_dmt="http://schemaserver/schemas/1.0/ik_dmt" xmlns:ik_om_dmt="http://schemaserver/schemas/1.0/ik_om_dmt" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://schemaserver/schemas/1.0/ http://schemaserver/schemas/1.0/schema-cs-commercial_services.xsd" schemaVersion="1.0">
   <control_area>
        <message_type>BPM_CANCEL_ORDER_OM</message_type>
        <source>GAM</source>
        <source_send_date>2004-01-14T12:54:00</source_send_date>
        <user_name>Danny</user_name>
        <message_id>1234567</message_id>
        <correlation_id>GAM_CID_28503</correlation_id>
   </control_area>
   <data_area>
        <ik_om_cor:bpm_cancel_order_om>
            <ik_om_cor:version_number>String</ik_om_cor:version_number>
            <ik_om_cor:cancel_request>
                <ik_om_dmt:email_addres_confirmation>.@aa.a</ik_om_dmt:email_addres_confirmation>
                <ik_om_dmt:order_nr>1000000000</ik_om_dmt:order_nr>
                <ik_om_dmt:request_date_time>2000-01-01T00:00:00x0Z</ik_om_dmt:request_date_time>
                <ik_om_dmt:bank_account>
                    <ik_om_dmt:bankaccount_nr>0</ik_om_dmt:bankaccount_nr>
                    <ik_om_dmt:bankaccount_type>B</ik_om_dmt:bankaccount_type>
                    <ik_om_dmt:bankaccountholder_city>String</ik_om_dmt:bankaccountholder_city>
                    <ik_om_dmt:bankaccountholder_name>String</ik_om_dmt:bankaccountholder_name>
                </ik_om_dmt:bank_account>
            </ik_om_cor:cancel_request>
            <ik_om_cor:maintenance_node>
                <ik_dmt:message_timestamp>2000-01-01T00:00:00x000Z</ik_dmt:message_timestamp>
                <ik_dmt:order_nr>1000000000</ik_dmt:order_nr>
            </ik_om_cor:maintenance_node>
        </ik_om_cor:bpm_cancel_order_om>
   </data_area>
</clientsystems>

The schemas for this XML file look like this:

schema-cs-commercial_services.xsd:

<schema xmlns="http://www.w3.org/2001/XMLSchema" xmlns:cs="http://schemaserver/schemas/1.0/" targetNamespace="http://schemaserver/schemas/1.0/" elementFormDefault="qualified" attributeFormDefault="unqualified">
    <include schemaLocation="http://schemaserver/schemas/1.0/schema-cs-control_area.xsd"/>
    <include schemaLocation="http://schemaserver/schemas/1.0/schema-cs-data_area.xsd"/>
    <include schemaLocation="http://schemaserver/schemas/1.0/schema-cs-error_area.xsd"/>
    <include schemaLocation="http://schemaserver/schemas/1.0/schema-cs-attachment_area.xsd"/>
    
    <element name="clientsystems">
        <annotation>
            <documentation>Schemaset version 1.0.16.1</documentation>
        </annotation>
        <complexType>
            <sequence>
                <element ref="cs:control_area"/>
                <element ref="cs:data_area"/>
                <element ref="cs:error_area" minOccurs="0"/>
                <element ref="cs:attachment_area" minOccurs="0"/>
            </sequence>
            <attribute name="schemaVersion" type="string" default="1.0"/>
        </complexType>
    </element>
</schema>

schema-cs-data_area.xsd:

bpm_cancel_order_om.xsd:

<?xml version="1.0" encoding="ISO-8859-1"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:ik_om_cor="http://schemaserver/schemas/1.0/ik_om_cor" xmlns:ik_om_dmt="http://schemaserver/schemas/1.0/ik_om_dmt" xmlns:ik_dmt="http://schemaserver/schemas/1.0/ik_dmt" targetNamespace="http://schemaserver/schemas/1.0/ik_om_cor" elementFormDefault="qualified" attributeFormDefault="qualified" version="1.0">
    <xs:import namespace="http://schemaserver/schemas/1.0/ik_dmt" schemaLocation="INET_DOMAIN_TYPES.xsd"/>
    <xs:import namespace="http://schemaserver/schemas/1.0/ik_om_dmt" schemaLocation="bpm_domain_types_om.xsd"/>
    <xs:element name="bpm_cancel_order_om" type="ik_om_cor:bpm_cancel_order_om"/>
    <xs:complexType name="bpm_cancel_order_om">
        <xs:sequence>
            <xs:element name="version_number" type="ik_dmt:Version_Number">
            </xs:element>
            <xs:element name="cancel_request" type="ik_om_dmt:Cancel_Request"/>
            <xs:element name="maintenance_node" type="ik_dmt:Maintenance_Node"/>
        </xs:sequence>
    </xs:complexType>
</xs:schema>

When I make an XML with data_area as root node, it validates ok. When I have clientsystems as root node, it does not. The following XML validates fine:

<?xml version="1.0" encoding="UTF-8"?>
<data_area xmlns="http://schemaserver/schemas/1.0/" xmlns:ik_om_coa="http://schemaserver/schemas/1.0/ik_om_coa" xmlns:ik_om_cor="http://schemaserver/schemas/1.0/ik_om_cor" xmlns:ik_dmt="http://schemaserver/schemas/1.0/ik_dmt" xmlns:ik_om_dmt="http://schemaserver/schemas/1.0/ik_om_dmt" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://schemaserver/schemas/1.0/
http://schemaserver/schemas/1.0/schema-cs-data_area.xsd">
    <ik_om_cor:bpm_cancel_order_om>
        <ik_om_cor:version_number>String</ik_om_cor:version_number>
        <ik_om_cor:cancel_request>
            <ik_om_dmt:email_addres_confirmation>.@aa.a</ik_om_dmt:email_addres_confirmation>
            <ik_om_dmt:order_nr>1000000000</ik_om_dmt:order_nr>
            <ik_om_dmt:request_date_time>2000-01-01T00:00:00x0Z</ik_om_dmt:request_date_time>
            <ik_om_dmt:bank_account>
                <ik_om_dmt:bankaccount_nr>0</ik_om_dmt:bankaccount_nr>
                <ik_om_dmt:bankaccount_type>B</ik_om_dmt:bankaccount_type>
                <ik_om_dmt:bankaccountholder_city>String</ik_om_dmt:bankaccountholder_city>
                <ik_om_dmt:bankaccountholder_name>String</ik_om_dmt:bankaccountholder_name>
            </ik_om_dmt:bank_account>
        </ik_om_cor:cancel_request>
        <ik_om_cor:maintenance_node>
            <ik_dmt:message_timestamp>2000-01-01T00:00:00x000Z</ik_dmt:message_timestamp>
            <ik_dmt:order_nr>1000000000</ik_dmt:order_nr>
        </ik_om_cor:maintenance_node>
    </ik_om_cor:bpm_cancel_order_om>
</data_area>

Can anyone tell me what's the problem here?

Greets,

Nils Gruson