AAA              Autonomous administrative area
AAP              Autonomous administrative point
ACDF             Access control decision function
ACI              Access control information
ACIA             Access  control  inner  administrative area
ACSA             Access  control specific administrative area
ACSE             Association control service element
ADMD             X.400 administration management domain
AE (Title)       Application entity (Title)
ANSI             American National Standards Institute
AOW              Asia Oceanic Workshop
AP               Administrative point
API              Application program interface
ASN.1            Abstract syntax notation one
AVA              Attribute value assertion
BER              Basic encoding rules (of ASN.1)
BSI              British Standards Institute
CA               Certification authority
CAN              Central Administration for the NADF
CCITT            International Telegraph and Telephone Consultative Committee (now the ITU-T)
CD               Committee draft (the first draft of a International Standard)
CN               Common name
COSINE           Cooperation for Open Systems Interconnection networking in Europe
DACD             Directory access control domain
DAM              Draft amendment to a standard
DAP              Directory access protocol
DCC              Data country code
DES              Data encryption standard, a US symmetric encryption algorithm
DFR              Document filing and retrieval, an ISO standard
DIB              Directory information base
DIS              Draft International Standard
DISP             Directory information shadowing protocol
DIT              Directory information tree
DL               X.400 distribution list
DMD              Directory management domain
DN               Distinguished name
DNIC             Data network identification code
DOP              Directory operational binding management protocol
DP               Draft proposal (the old name for a CD)
DSA              Directory system agent
DSE              DSA specific entry
DSP              Directory system protocol
DUA              Directory user agent
EC               European Community
ECMA             European Computer Manufacturer's Association
EDI              Electronic data interchange
EEMA             European Electronic Messaging Association
EIT              X.400 encoded information type
EWOS             European Workshop for Open Systems
FIPS             A US Federal information processing standard
FTAM             File  transfer, access and  management, an ISO standard
F.500            A CCITT specification for administration supplied directory services
HCI              Human-computer interface
HOB              Hierarchical operational binding
IAP              Inner administrative point
ICD              International code designator
ID               Identifier
IEC              International Electrotechnical Commission
ILL              Inter-library loan service
IS               International Standard
ISP              International Standardised Profile
ISO              International Standards Organization
ITU-T            International Telecommunication Union - Telecommunication Standardisation Bureau (formerly the CCITT)
LDAP             Lightweight directory access protocol
MHS              X.400 message handling system
MTA              X.400 message transfer agent
MTS              X.400 message transfer system
NADF             North American Directory Forum
NHOB             Non-specific  hierarchical  operational binding
NIST             US National Institute for Standards and Technology
NSAP             Network service access point
NSSR             Non-specific subordinate reference
OID              Object identifier
OIW              OSI Implementors Workshop (sponsored by NIST)
OPAC             Online public access catalogue
O/R address      X.400 message originator/recipient address
OSI              Open Systems Interconnection
PDAM             Provisional  draft  amendment to a standard
PRMD             X.400 private management domain
PSS              Packet switch stream - an X.25 service
Quipu            A  publicly available implementation of X.500, that runs under UNIX
RDN              Relative distinguished name
RFC              Request for comment, an electronic document published on the Internet
RHOB             Relevant hierarchical operational binding (i.e. either HOB or NHOB)
ROSE             Remote operations service element
SDSE             Shadowed DSE
SMTP             Simple  mail  transfer protocol - the Internet standard for electronic mail
SOB              Shadow operational binding
SR               Library search and retrieval service
TCP/IP           Transmission control protocol/Internet protocol, an Internet standard for interconnecting computers
TLV              Type-length-value, the ASN.1 method for encoding bytes
TP               Transaction processing
UA               X.400 user agent
UTC              Co-ordinated universal time
WIMP             Windows, icons, menus and pointers
X.25             A CCITT specification for the network service
X.400            A CCITT  specification  for  message handling systems
X.500            A CCITT specification for directory services