Information systems are developed over time using different DBMSs and may be owned by different parts of an organization. As a result, data are fragmented across a number of systems, organizational, and geographic boundaries. A virtual database is a type of database management system that serves as a container to transparently view and query several other databases through a uniform application programming interface (API) that culls from multiple sources as if they were a single entity. These databases are connected via a computer network and then accessed as if they are from a single database. The goal for a virtual database is to be able to view and access data in a unified way without needing to copy and duplicate it in several databases or manually combine the results from many queries. They are also known as federated databases.