Here are some schemas about Postgis Topology data model.
Images and schema about organisation :
http://trac.osgeo.org/postgis/attachment/ticket/2578/postgis_topology_data_model_explained.png http://trac.osgeo.org/postgis/attachment/ticket/2578/postgis_topology_data_model_explained%20%281%29.png http://trac.osgeo.org/postgis/attachment/ticket/2578/postgis_topology_data_model_explained%20%282%29.png http://trac.osgeo.org/postgis/attachment/ticket/2578/postgis_topology_data_model_explained%20%283%29.png http://trac.osgeo.org/postgis/attachment/ticket/2578/postgis_topology_data_model_explained%20%284%29.png http://trac.osgeo.org/postgis/attachment/ticket/2578/postgis_topology_data_model_explained%20%285%29.png http://trac.osgeo.org/postgis/attachment/ticket/2578/postgis_topology_data_model_explained%20%286%29.png
A detailled explanation table by table, field by field of postgis_topology data model (DB wise)