This Recommendation | International Standard specifies a set of Packed Encoding Rules that may be used to derive a transfer syntax for values of types defined in ITU-T Rec. X.680 | ISO/IEC 8824-1. These Packed Encoding Rules are also to be applied for decoding such a transfer syntax in order to identify the data values being transferred. The encoding rules specified in this Recommendation | International Standard: — are used at the time of communication; — are intended for use in circumstances where minimizing the size of the representation of values is the major concern in the choice of encoding rules; — allow the extension of an abstract syntax by addition of extra values, preserving the encodings of the existing values, for all forms of extension described in ITU-T Rec. X.680 | ISO/IEC 8824-1; — can be modified in accordance with the provisions of ITU-T Rec. X.695 | ISO/IEC 8825-6.