Virtual Graph
Figure 4. A virtual graph with embedded hierarchies of adlets.
A virtual graph consists of nodes N = {n1, ...., nk} and arcs
A = {a1, ..., an}. Each node ni = (Si, Ti) is defined by a site Si and an
adlet tree Ti. An arc (ni, nj) connects one node ni
and another node nj if the two sites Si and Sj are conceptually related.
Initially the virtual graph contains only a single node ni for the local
site Si. Suppose this site has documents doc1, .., dock, the corresponding
adlet tree Ti contains adlet1, ....., adletk, organized into a
tree. Notice we assume the documents in a site, and thus the
corresponding adlets, can be organized into a conceptual hierarchy.