directory access protocol (X.500) (DAP)

The Directory Access Protocol (DAP) is a protocol defined by the International Standards Organization( ISO) for X.500 to access directory services, based on OSI protocols.

The individual components of the DAP service, the X.500 server and the X.500 client, cooperate together to manage information about objects such as organizations, countries, companies, people, machines, and so on, in the global scope. The DAP protocol acts in an X.500 user directory between the Directory User Agents( DUA) and the Directory System Agents( DSA) and can retrieve or search the information according to certain criteria.

Some of the DAP functionality was incorporated into the Lightweight Directory Access Protocol( LDAP), developed in 1993, which is built on top of TCP/ IP and is therefore more commonly implemented than the DAP protocol. There is also the Connectionless Lightweight Directory Access Protocol( CLDAP), which works without connections.