Inside a Virtual Acoustic Object

VAO 0.5.0 separates the semantic release from its physical carriers. The manifest describes resources and their relationships. A carrier packages exact realizations of those resources for transport. Changing the delivery arrangement does not, by itself, create a different semantic release.

Three carrier roles#

A small, explicit container#

instrument.vao
├── mimetype
├── vao-manifest.json
├── META-INF/
│   └── vao-carrier.json
└── payload/
    └── …

The manifest fixes semantic identity. The carrier descriptor maps embedded payload members to that manifest. Byte sizes and SHA-256 digests let a client check whether a retrieved realization is the one the release actually identifies.

From a resource to its exact bytes#

A filename is a convenient label, not an identity guarantee. Re-encoding audio, editing a mesh or replacing an image changes the exact realization. Even when two files serve the same intellectual role, a client must not substitute one for the other without an explicit release description. A changed URL can still deliver the same realization; an unchanged URL can deliver different bytes.

What happens during selective delivery#

• Read the bootstrap manifest and establish the fixed semantic release being requested.
• Choose a declared group, including its dependencies, that supports the intended use.
• Resolve the pinned preservation carrier and exact member mapping.
• Retrieve the member, then check its decoded byte length and SHA-256 against the manifest.
• Record the selection and materialized carrier so that a later user can understand what was acquired.

A small carrier is not automatically a complete preservation copy. Group completeness is a statement about included realizations and their recursively required groups. A browser preview might be sufficient for inspecting an image, while a later acoustic analysis needs another group. The release contract makes that difference explicit instead of letting a partial download masquerade as the whole object.

Say how each representation came into being#

VAO 0.5.0 distinguishes statuses including captured, authored, converted, derived, simulated, inferred, reconstructed, redacted, hybrid and undetermined. These labels locate a representation within its history. A captured signal and a simulated signal may both be playable, but their scientific roles differ. A converted encoding preserves a relationship to an input; a reconstructed surface embodies additional assumptions. Retain the derivation evidence needed to interpret the chosen status.

Use exact realization identity when citing or comparing output. “The organ model” is too broad if a release contains a measured point cloud, a reconstructed mesh and a reduced mobile geometry. Name the relevant realization and retain its byte identity, then explain the relation it has to the other forms of the asset.