The Directory Assistance Service (DAS) is an obsolete protocol and service for accessing X.500 directory services. DAS was intended to provide a lighweight means for clients to access X.500 directory services via a split-Directory User Agent model. Here the Directory User Agent (DUA) (the directory client) is split into a Directory Assistance (DA) client and a Directory Assistant. The directory user would interact with the DA-client, the DA-Client would communicate with the Directory Assistant using the DA protocol, and the Directory Assistant would communicate with the Directory Service using the X.500 Directory Access Protocol (DAP). That is, the Directory Assistant is a Directory Assistance protocol to DAP gateway. This design allows the DA-client to access the directory without requiring it to support the cumbersome Open Systems Interconnection protocol stack. In the field of telecommunications, a communications protocol is the set of standard rules for data representation, signalling, authentication, and error detection required to send information over a communications channel. ... In economics and marketing, a service is the non-material equivalent of a good. ... X.500 is the set of ITU-T computer networking standards covering electronic directory services such as white pages, Knowbot and whois. ... The Open Systems Interconnection (usually abbreviated to OSI) was a new effort in networking started in 1982 by the International Organization for Standardization (ISO), along with the ITU-T. Prior to OSI, networking was completely vendor-developed and proprietary, with protocol standards such as SNA and DECnet. ...

The Directory Assistance Service was created in 1990 by Marshall T. Rose while at Performance Systems International, Inc., and formally specified in RFC 1202 (published in 1991).

These and related efforts, such as DIXIE, lead to the development of the Lightweight Directory Access Protocol. LDAP replaced the Directory Assistance Service. DIXIES LAND, 1904 postcard Dixie is a nickname for the Southern United States. ... In computer networking, the Lightweight Directory Access Protocol, or LDAP, is a networking protocol for querying and modifying directory services running over TCP/IP. An LDAP directory usually follows the X.500 model: It is a tree of entries, each of which consists of a set of named attributes with...