Diagram of the ScaleNet data model. The central tables to the database are the Citations, Scale Classification, Species and Genera tables. Together these tables validate the currently accepted valid names of scale insects, which are then used throughout the database to track ecological associations, distributions, taxonomic keys, etc. The figure depicts relationships between the tables using Crow's Foot Notation. The symbol k represents a one-and-only-one relationship. The crow's foot symbol represents a one-or-many relationship. Relationships can be asymmetrical, and the nature of the relationship of object A to object B is specified at the connection with B. For example, the relationship between Keys and Keys Stages would be read as 'One key can have one and only one key stage; a key stage can be in one or many keys.'