Overview of the EndoNet structure. A: Shown are the major entities of the database and their connections. In this abstract outline, all attributes and entities that are only needed for database modeling, like the subunits of the hormones and receptors, are omitted. Also the entities referring to the literature sources and comments are left out. Each shown entity has a commented connection to literature. The entities which are marked with an asterisk can be searched by their name in the web interface. All entities can be retrieved by their ID. B: Transformation of the complete network to the signal flow network. The opaque entities and relations are removed and their information has been moved to the neighboring entities. The red relations are inserted for modeling the signal flow network.