Importing XML Schema

EDIT: Made slight change. I think I got a little closer, but still not working. All current info is as follows:

I successfully created an XSD file to validate an XML file, however I would like to split up the XSD file into another file. I believe I need to use an import element in the XML file to do that, but I am struggling to get it to work. Here is what I have right now at the top of the XML file:

<?xml version="1.0" encoding="UTF-8"?>
<presentations xmlns="http://www.brett.com/presentations"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.brett.com/presentations presentations_vb.xsd"
>

Here is the top part of the main XSD file:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns="http://www.brett.com/presentations"
targetNamespace="http://www.brett.com/presentations"
elementFormDefault="qualified">

<!-- Here is the line in question -->
<xs:import namespace="http://www.brett.com/presentations/topic" schemaLocation="http://www.brett.com/presentations topic_vb.xsd" />

Here is the new XSD file that I am trying to import:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns="http://www.brett.com/presentations/topic"
targetNamespace="http://www.brett.com/presentations/topic"
elementFormDefault="qualified">

<!-- Topic Element -->
    <xs:complexType name="topicType">
      <xs:simpleContent>
        <xs:extension base="xs:string">
          <xs:attribute name="genre" use="required">
            <xs:simpleType>
              <xs:restriction base="xs:string">
                <xs:enumeration value="ART" />
                <xs:enumeration value="Music" />
                <xs:enumeration value="Science" />
                <xs:enumeration value="Technology" />
              </xs:restriction>
            </xs:simpleType>
          </xs:attribute>
        </xs:extension>
      </xs:simpleContent>
    </xs:complexType>

    <xs:element name="topic" type="topicType" />
</xs:schema>

Everything was well-formed and validated prior to breaking up the XSD into two files. I'm pretty sure I'm importing it wrong, but I can't figure out the proper way. I'm getting the following error when trying to validate the XML file (the XSD files still validate): "FatalError at line 0, column 0: unsupported protocol in URL"

Can anyone help?