This extended version of the SELECT clause assigns a filename to an XML stream.

where myxmlfile is the name of the file. Generally, XML files use the file extension .xml.
where myprog is the name of a program that uses stdin and/or stdout to communicate through the pipe.
The following code:
SELECT xml-addressdb
ASSIGN 'address.xml'
ORGANIZATION IS XML
DOCUMENT-TYPE IS OMITTED
FILE STATUS xml-status.
Is equivalent to:
SELECT xml-addressdb
ASSIGN 'address.xml'
ORGANIZATION IS XML
FILE STATUS xml-status.
SELECT foobar
ASSIGN TO "foobar.xml"
ORGANIZATION IS XML
DOCUMENT TYPE IS "foobar.xsd"
CHECK VALIDITY ON INPUT
CHECK OUTPUT.