When a communicated message is based on reference to another message, it is called a

When a communicated message is based on reference to another message, it is called a meta message.

A meta message is communication about communication, a message that points to another message.

A sourced message merely names one with an identified source, not one referring to another message.

A referential message points to an external object or fact, not to another message itself.

An ancillary message is a supporting or secondary message, not one built on reference to another.

The prefix meta marks this message as standing above and about another.