PostgreSQL is a free software object-relational database management system (ORDBMS), released under a BSD-style license. It offers an alternative to other database systems. Similar to other free software projects such as Apache, GNU/Linux, and MediaWiki, PostgreSQL is not controlled by any single company, but relies on a global community of developers and companies to develop it. PostgreSQL features the ability to define types, but also the ability to fully describe relationships. In PostgreSQL, the database "understood" relationships, and could retrieve information in related tables in a natural way using rules. Tables can be set to inherit their characteristics from a "parent" table. nheritance provides a way to map the features of generalization hierarchies depicted in Entity Relationship Diagrams (ERD) directly into the PostgreSQL database. Phppgadmin is a web application written with PHP to manage the PostgreSQL database.