|XDR, External Data Representation|
|Type:||Data description language.|
|Working groups:||nfsv4, Network File System Version 4.|
XDR is a standard for the description and encoding of data. It is useful for transferring data between different computer architectures, and has been used to communicate data between such diverse machines as the SUN WORKSTATION*, VAX*, IBM-PC* and Cray*. XDR fits into the ISO presentation layer, and is roughly analogous in purpose to X.409, ISO Abstract Syntax Notation. The major difference between these two is that XDR uses implicit typing, while X.409 uses explicit typing.
XDR uses a language to describe data formats. The language can only be used only to describe data; it is not a programming language. This language allows one to describe intricate data formats in a concise manner. The alternative of using graphical representations (itself an informal language) quickly becomes incomprehensible when faced with complexity.
[RFC 1014] XDR: External Data Representation Standard.
[RFC 1790] An Agreement between the Internet Society and Sun Microsystems, Inc. in the Matter of ONC RPC and XDR Protocols.
[RFC 4506] XDR: External Data Representation Standard.
[RFC 1832] XDR: External Data Representation Standard.