The Directory Assistance Service (DAS) is an obsolete

protocol Protocol may refer to: Sociology and politics * Protocol (politics), a formal agreement between nation states * Protocol (diplomacy), the etiquette of diplomacy and affairs of state * Etiquette, a code of personal behavior Science and technology ...

and

service Service may refer to: Activities * Administrative service, a required part of the workload of university faculty * Civil service, the body of employees of a government * Community service, volunteer service for the benefit of a community or a pu ...

for accessing

X.500 X.500 is a series of computer networking standards covering electronic directory services. The X.500 series was developed by the ITU-T, Telecommunication Standardization Sector of the International Telecommunication Union (ITU-T). ITU-T was former ...

directory services. DAS was intended to provide a lightweight 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 The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communicatio ...

protocol stack. The Directory Assistance Service was created in 1990 by

Marshall Rose Marshall T. Rose (born 1961) is a network protocol and software engineer, author, and speaker who has contributed to the Internet Engineering Task Force (IETF), the Internet, and Internet and network applications. More specifically, he has special ...

while at Performance Systems International, Inc., and formally specified in RFC 1202 (published in 1991). It was an evolution of the DISH client/server interface in

Quipu ''Quipu'' (also spelled ''khipu'') are recording devices fashioned from strings historically used by a number of cultures in the region of Andean South America. A ''quipu'' usually consisted of cotton or camelid fiber strings. The Inca people u ...

, developed by Colin Robbins while at

University College London , mottoeng = Let all come who by merit deserve the most reward , established = , type = Public research university , endowment = £143 million (2020) , budget = ...

. These and related efforts, such as

DIXIE Dixie, also known as Dixieland or Dixie's Land, is a nickname for all or part of the Southern United States. While there is no official definition of this region (and the included areas shift over the years), or the extent of the area it cover ...

, led to the development of the

Lightweight Directory Access Protocol The Lightweight Directory Access Protocol (LDAP ) is an open, vendor-neutral, industry standard application protocol for accessing and maintaining distributed directory information services over an Internet Protocol (IP) network. Directory servi ...

.{{cite web, title=Pre-History of LDAP, url=http://cybermatters.info/2013/04/09/prehistory-of-ldap/, website=Cyber Matters, accessdate=5 October 2014 LDAP replaced the Directory Assistance Service.

References

Internet protocols