There does not seem to be any way to walk the CPE tree for "previous". It
cannot be done by the names, as Windows NT 4.0, Windows 2000, Windows XP and
Windows 7 have a commonly known order, but nothing machine-discernable seems
to exist to denote "previous".
Would there be any way to carry this mapping across product names / vendors?
If I recall correctly, iPlanet 4.0 was acquired and became Sun iPlanet 4.1,
then Sun ONE Web Server 5, then Sun Java System Web Server 6 and 7. Iplanet
and Sun ONE would both be candidates for "previous" in relation to Sun Java
System Web Server 7.