ISO/IEC 8824-1:2021

This document provides a standard notation called Abstract Syntax Notation One (ASN.1) that is used for the definition of data types, values, and constraints on data types.
This document:
–      defines a number of simple types, with their tags, and specifies a notation for referencing these types and for specifying values of these types;
–      defines mechanisms for constructing new types from more basic types, and specifies a notation for defining such types and assigning them tags, and for specifying values of these types;
–      defines character sets (by reference to other Recommendations and/or International Standards) for use within ASN.1.
The ASN.1 notation can be applied whenever it is necessary to define the abstract syntax of information.
The ASN.1 notation is referenced by other standards which define encoding rules for the ASN.1 types.