1. A computer readable storage medium comprising computer usable program code: executed to perform operations for collaboration between a plurality of associated portlets in a portal server, the operations comprising: defining a common Portlet Application Session Object, the Portlet Application Session Object comprising a data store session object and configured to allow each portlet in a portlet application to share session information; associating each portlet in a portlet application with a portlet descriptor describing a dynamic context name, each portlet configured to access the common Portlet Application Session Object, the dynamic context name referencing a dynamic context configured to be changed during runtime; and forming collaboration groups of portlets having corresponding dynamic context names, a collaboration group being a subgroup of the group of portlets in the portlet application, the portlets in each collaboration group sharing dynamic context changes through the Portlet Application Session Object.