Does the XML file have to contains XSL instructions?

[Ben Stover]

When I apply a simple XSL stylesheet on a simple XML file then Xalan v2.7.1 
complains about missing xsl-stylesheet instructions in the XML file.

I used a command like the following:

java org.apache.xalan.xslt.Process -in some.xml -xsl convert.xslt

...and got:

Exception in thread "main" java.lang.RuntimeException: No processing 
instruction found for xml-stylesheet in some.xml.
        at org.apache.xalan.xslt.Process.doExit(Process.java:1155)
        at org.apache.xalan.xslt.Process.main(Process.java:1128)

Why?

I am using java v1.5 under WinXP. 

Ben