We are developing application on Java that includes
XSL Transformation (jdk1.4 , xalan)
The task is: get file ss_1.xsl, parse and store result in
the memory. Then get ss_2.xsl and import ss_1.xsl (stored
result) into it using program facilities.
After that the result should be usable as single stylesheet.

It's already worked with xalan-1.*, but I can handle that
with xalan-2.*.

Look up javax.xml.transform.TransformerFactory.setURIResolver
and javax.xml.transform.URIResolver. Implement your own
URIResolver which reads preparsed stuff from memory for
matching URLs. Use <xsl:import> or <xsl:include> to import
ss_1.xsl from ss_2.xsl.

Or just have a look at Cocoon
 http://xml.apache.org/cocoon/