VAO Dynamic Delivery profile 0.6.0

Profile IRI: https://w3id.org/modavis/vao/profile/dynamic-delivery/0.6.0

Applicability

Every VAO 0.6.0 manifest embeds and claims this profile, even when its only distribution is an embedded preservation closure. This guarantees a common model for carriers, exact acquisition, and materialization.

Requirements

• Asset groups state selection set, quality tier, availability, selection policy, realization IDs, dependencies, total byte size, capabilities, materialized profiles, and cache policy. Every materialized-profile IRI resolves to an embedded Profile record.
• Dependency and fallback graphs are resolvable and acyclic.
• Repository distributions identify immutable record/file versions; pack members identify exact pack and pack-manifest digests. A carrier-member distribution identifies an exact carrier in the release descriptor and the immutable repository record/file that transports it.
• A carrier has a release-stable identifier, maps every embedded file exactly once, and verifies it against the realization.
• Complete groups include their transitive dependencies.
• Bootstrap carriers embed at least one realization; preservation closures embed all and mark all groups complete.
• Materialization verifies decoded byte size and SHA-256 before making data available.
• Receipts describe local acquisition results without mutating the release. They pin the producing implementation and exact source-carrier descriptor (plus the complete packed-container identity when applicable), distinguish attempt from successful verification, and use status-dependent evidence. An acquisition Distribution resolves through the acquired Realization; already embedded bytes are carrier evidence rather than a fabricated Distribution acquisition. Inaccessible/policy-blocked outcomes carry diagnostics but never acquired-byte identity.

Capability negotiation

Groups list the capabilities needed to use their realizations. Materializable profiles list the groups required to activate a profile. A client may choose a compatible quality tier based on capability, access, byte budget, and cache policy, but must not relabel a fallback as the selected exact realization.

Network acquisition is optional. Offline validation of embedded data remains possible.

Cross-carrier acquisition

carrier-member is used when a bootstrap carrier describes bytes held in a larger carrier of the same release. The Distribution records the target carrierId, repository binding, immutable version persistent identifier, repository record identifier, and carrier filename. The member path is intentionally not copied into the semantic manifest: it is read from the target carrier descriptor, whose digest is fixed by vao-release.json.

A resolver MUST match all four target fields—carrier ID, version PID, record ID, and file identifier—against the release descriptor before fetching a member. It then verifies the carrier descriptor, finds the realization-to-path mapping, and verifies the decoded member bytes against the manifest. A concept DOI, an unversioned “latest” URL, or a filename alone is insufficient.

The outer .vao SHA-256 is recorded in the external release descriptor, not inside the carrier. This avoids a self-hash cycle. The carrier descriptor fixes the exact manifest and its embedded-member map; the manifest fixes every realization byte identity.

Materialized carriers

A client may create a custom carrier for any closed set of groups or realizations. That carrier embeds the unchanged manifest plus the selected, verified bytes and receives its own carrier ID. It is a local transport object, not a new semantic release. Converting media creates new realization bytes and therefore requires explicit derivation records; it is not ordinary materialization.

Mandatory capability IRIs

• https://w3id.org/modavis/vao/vocab/capability/immutable-release
• https://w3id.org/modavis/vao/vocab/capability/carrier-mapping