The common domain is used by ETSI Technical Bodies for ASN.1 definitions which will be used in more than one ETSI deliverable.

Only a limited number of values are available.

See the 
List of ETSI Object Identifiers 
to see which values have been allocated in the Common Domain, and how to request assignment of an object identifier in this domain.

At present, only one value under this domain is allocated:  value 0 is used for ETSI Identified 
Organizations.
 
See the
List of ETSI Object Identifiers
to see which values have been allocated and how to request assignment of an object identifier for an ETSI Identified Organization.

The remaining values in this domain are reserved for future use

This is the most commonly used form of ASN.1 Object Identifier in ETSI.

The object identifier tree value for a given ETSI deliverable is derived by deleting the first digit of its document number (and omitting leading zeroes).

EXAMPLE 1: The allocated value for ETS 300 182 is "182", or "0 4 0 182" in full.

EXAMPLE 2: The allocated value for TS 101 123 is "1123".  The allocated value for ES 201 123 is "1123", or "0 4 0 1123" in full

NOTE: The assignment of document numbers is independent of ETSI deliverable type. Technically, TS 101 123 and ES 201 123 are just two different versions of the same document.