Specification: DagCBOR

August 20, 2019 ยท View on GitHub

Status: Descriptive - Draft

DagCBOR supports the full IPLD Data Model.

CBOR already natively supports all IPLD Data Model Kinds.

Format

The CBOR IPLD format is called DagCBOR to disambiguate it from regular CBOR. Most CBOR objects are valid DagCBOR. The only hard restriction is that any field with the tag 42 must be a valid CID.

As with all IPLD formats, DagCBOR must be able to encode Links. In DagCBOR, links are CIDs encoded using the raw-binary identity Multibase. That Multibase prefix (0x00) must not be omitted. They are stored as byte-string type (major type 2), with the tag 42.

(the inclusion of the Multibase exists for historical reasons)

Map Key Restriction

In DagCBOR, map keys must be strings.

Canonical DagCBOR

Canonical DagCBOR must:

  1. Use no tags other than the CID tag (42). Other tags may be lost in conversion.
  2. Use the canonical CBOR encoding.