1. A database system comprising a processor operable to execute computer program instructions, a memory operable to store computer program instructions executable by the processor and data processable by the processor, data stored in the memory and processable by the processor, and computer program instructions stored in the memory and executable to process the data to implement: a plurality of database objects, each database object having a level of security, at least some of the database objects comprising data; a plurality of security factors, each security factor representing a characteristic of a user of the database system attempting to access data in the database system, including a physical security factor type indicating a physical, network, or database characteristic of the user, an implementation security factor type indicating a user-defined, application, or certificate information characteristic of the user, or an environmental security factor type indicating a time-based characteristic of the user; at least one database session of the user in the database, the database session having a level of security, the user communicatively connected to the database with one of a plurality of network domains, each network domain having a level of security; and a plurality of realms, each realm comprising a set of database schemas used by an application and each realm defining a privilege of the user of the database system relative to a schema of the database system; wherein the database system is operable to grant or deny access to the data to a user based on the security factors associated with the user, based on a privilege of the user defined by at least one realm, based on the level of security of the data, based on the level of security of the database session, and based on the level of security of the network domain, and wherein each unit of data is created by one the plurality of network domains and the database system is further operable to provide access to the unit of data to a network domain independently of which network domain created the unit of data.