The relation between a document and the information that presents it is a binary relation (the information presents the document or not).
this set of docu-1 http://sourceforge.net/projects/conexp/ Figure 3: there are a one concept contains in its intent the query terms (surrounded by a green circle) ments (noted R d ) to do this, we look for documents that satisfy to the query Q = t 5 ∧ t 6 ∨ t 2 .