SchemaLocation

In pain.001.001.03 schema location is recommended with value "urn:iso:std:iso:20022:tech:xsd:pain.001.001.03"

For example the following is a correct way to present the <Document> tag:

<?xml version="1.0" encoding="UTF-8"?> 
<Document xmlns="urn:iso:std:iso:20022:tech:xsd:pain.001.001.03" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="urn:iso:std:iso:20022:tech:xsd:pain.001.001.03 pain.001.001.03.xsd"> 

Recommended part

Optional part, used to describe the physical location of the schema. In XMLspy, for example, it's used for validating the file against schema.