Serialisation

Serialisation (JSON-LD)

Canonical form

The canonical serialisation of the CDM is JSON-LD 1.1. Concert publishes the SIGNET @context at a stable URI:

https://concert.foundation/signet/v0.1/context.jsonld

Every object type and property resolves to a URI in the SIGNET vocabulary namespace (https://concert.foundation/signet/v0.1/vocab#), itself aligned to ePO terms where equivalents exist. Every worked example begins with:

{ "@context": "https://concert.foundation/signet/v0.1/context.jsonld", "type": "...", ... }

Plain-JSON consumption

Consumers that do not process linked-data semantics MAY treat CDM documents as ordinary JSON; the @context is ignorable without loss of the document's tree structure. This preserves the low-friction adoption that made OCDS's plain-JSON approach successful (design principle 1.8) — you can validate, read, and write SIGNET documents with nothing more than a JSON parser and the JSON Schema.

What the context aligns

The shipped schema/context.jsonld maps SIGNET terms onto external vocabularies:

Namespace prefix	IRI
signet	https://concert.foundation/signet/v0.1/vocab#
ePO	http://data.europa.eu/a4g/ontology#
prov	http://www.w3.org/ns/prov#
vc	https://www.w3.org/2018/credentials#

Object types map to the SIGNET vocabulary:

Party, SourcingEvent, Submission, Decision, Policy, SyntheticAgent, Mandate, Event, Consent → signet:*.

Selected properties map to external ontologies so SIGNET data is interpretable by existing toolchains:

SIGNET term	Maps to
id	@id
type	@type
madeBy	prov:wasAttributedTo
generatedBy	prov:wasGeneratedBy
derivedFrom	prov:wasDerivedFrom
procuringParty	ePO:hasBuyer
submittingParty	ePO:hasTenderer

This single context is what lets the CDM align simultaneously with OCDS (JSON), W3C VC/DID (JSON-LD), ePO (RDF/OWL), and Solid (RDF) — see Standards Mapping.

Cryptographic envelopes

Where confidentiality is required — sealed-bid submissions (Submission.sealedProof) or selective credential disclosure (Credential.selectiveDisclosure) — the relevant fields carry a cryptographic envelope (zero-knowledge proof, homomorphic ciphertext, or BBS selective-disclosure proof) in place of cleartext, with verification metadata.

The envelope formats are specified in the separate SIGNET Cryptographic Profiles document (not in this repository).

Identifiers and namespaces

• Every CDM object MUST carry a network-unique id.
• DIDs are RECOMMENDED for Parties and agents; URN/URI identifiers are acceptable for process objects.
• The SIGNET vocabulary namespace, the published @context, and the registry of identifier schemes and codelists are maintained by Concert at stable URIs under concert.foundation and MUST NOT be repurposed by implementers to publish non-conforming extensions under the SIGNET name.

Where to go next

• Validation & Conformance — validating the JSON.
• Trust Layer → Provenance — the PROV mapping in use.