This document describes a CBOR tag for multimaps encoded as arrays of pairs.
Tag value: TBD280
Data item: Array (major type 4)
Semantics summary: Array of key-value pairs where keys may be duplicated.
This tag represents an array of key-value pairs where keys may be duplicated. Each key-value pair is encoded as a two-element subarray of major type 4, size 2 (header byte 0x82). The keys and values may be of any valid CBOR type and need not be homogenous.
According to RFC7048, section 2-1:
A map that has duplicate keys may be well-formed, but it is not valid, and thus it causes indeterminate decoding
This limitation makes it either impossible or unpractical to encode multimap data structures as CBOR maps (major type 5).
A workaround is to encode multimap data structures as arrays of pairs. This tag allows a CBOR decoder to determine a priori that the following array is indeed an array of pairs and can thus be safely interpreted as a multimap.