WSDL Elements - complexType

I thought I knew, but maybe I don't...I'm trying to create a WSDL that can
be imported into Websphere Commerce. The Websphere Commerce system will use
that definition to consume a web service that I will create with RPG-XML. I
need to have a proper and correct WSDL so the Websphere Commerce system
generates the right Java code. I've created WSDLs where I had simple
elements, but I'm trying to have groups of elements. The WSDL is not
correct (as per Altova XML Spy and as per SoapUI). I have this as part of
the WSDL:

<xsd:complexType name="ShoppingCartOperationResponse">
<xsd:sequence>
<xsd:element name="EchoInput" type="EchoInputType"
minOccurs="1" maxOccurs="20"/>
<xsd:element name="SKUPromo" type="SKUPromoType"
minOccurs="0" maxOccurs="20"/>
<xsd:element name="Delivery" type="DeliveryType"
minOccurs="0" maxOccurs="1"/>
<xsd:element name="CPU" type="CPUType" minOccurs="0"
maxOccurs="5"/>
</xsd:sequence>
</xsd:complexType>
<xsd:complexType name="EchoInputType">
<xsd:sequence>
<xsd:element name="inSKU" type="xsd:string"></xsd:element>
<xsd:element name="inQuantity" type="xsd:string"></xsd:element>
<xsd:element name="inFloor" type="xsd:string"></xsd:element>
<xsd:element name="inPromoNum1" type="xsd:string"></xsd:element>
<xsd:element name="inPromoNum2" type="xsd:string"></xsd:element>
<xsd:element name="inZip" type="xsd:string"></xsd:element>
<xsd:element name="inCity" type="xsd:string"></xsd:element>
<xsd:element name="inState" type="xsd:string"></xsd:element>
<xsd:element name="inStore" type="xsd:string"></xsd:element>
<xsd:element name="outErrMsg" type="xsd:string"></xsd:element>
</xsd:sequence>
</xsd:complexType>

I thought I could define EchoInput as type=EchoInputType, and then define
EchoInputType as a complexType with the element definition. When I try
that, I get this in Altova XML Spy:

Invalid XML schema: ''EchoInputType' must refer to an existing simple or
complex type.'

Any ideas as to how I can do this? Thanks!