Relative Namespace in XML/XSD

I have the following XML document that validates fine using the absolute paths for the namespaces.

<?xml version="1.0" encoding="UTF-8"?>
<Inventory xsi:schemaLocation="http://www.acme.com/schema URL" xmlns="http://www.acme.com/schema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

However, how do I make the namespaces relative to the location of the XML document? The XML documents are located in /application/files and the schemas (.xsd) are located in /application/schema. I tried to format the header as

<?xml version="1.0" encoding="UTF-8"?>
<Inventory xsi:schemaLocation="../schema ../schema/inventory.xsd" xmlns="../schema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

But that doesn't work. Any thoughts?