Hi,
a portlet shows in a restricted area a web application. Nowdays when you develop a Java Web Application you usually want to use web framework like
struts,
jsf, seam, and others maybe. But what happen when you try to expose a portlet develop with a web framework?
The portal management of URL interfer with the URL managament of the web framework, hence with just jsr-168 or 286 portlet spec you only have a standard in managing the lifecycle of portlets and deployment descriptor but no other.
JSF is a
jee spec and Java community is working on jsr-301 for a JSF portlet bridge that let you expose transparently a jsf app into a portlet. There also Struts Portlet bridge, some open some propietary (oracle for its oracle portal server).
WebLogic Portal PageFlow is simply an extension of the Struts Framework that che be used in a portlet, PageFlow technology is available since WebLogic Portal 8.1: if i'm not wrong WLP 8.1 GA was released in year 2003 nearly at the same time when jsr 168 was released.
Regards
Stefano