1. A computer program product stored in an internal memory of a digital computer for dynamically assembling a topology tree of a portal page, comprising: instructions for loading an existing topology tree of a portal page from storage, wherein the existing topology tree comprises a plurality of nodes; instructions for marking a node of the plurality of nodes of the existing topology tree a dynamic node, wherein said dynamic node comprises a node of said plurality of nodes that references a fragment placeholder, and wherein said fragment placeholder comprises a node that is to be resolved at runtime; instructions for assigning, by a dynamic assembly module, an adapter to said dynamic node; instructions for creating, using said adapter, a topology tree fragment, wherein said topology tree fragment comprises a partial topology tree that is built at runtime; instructions for replacing, by said dynamic assembly module, said fragment placeholder with said topology tree fragment at runtime; and instructions for assigning an expiry time to the topology fragment, wherein the topology fragment does not change for a given period of time, wherein said instructions for replacing, by said dynamic assembly module, said fragment placeholder with said topology fragment at runtime, comprises: instructions for replacing, by said dynamic assembly module, said fragment placeholder at runtime if said expiry time is not expired.