Before proceeding to the models for each page type, we include here
the ER model for the system catalog. This model was produced in the
analysis phase, however currently the tool does not store any information about
the structure of the tables and views (queries). Study of the model is
still important, as it is a
complement to the ER models of the pages. Also the system catalog may be
implemented in the future, if we decide to extend XPage from a "tool" to an
"integrated software development environment".