Since MGNLDAM-411, one may implement a custom AssetMetadataDefinition. These implementations are bound to the AssetMetadataRegistry via @Multibinding.

However, both JcrAsset and JcrAssetProvider limit their support to MagnoliaAssetMetadata and DublinCore, plain hard-coded.

• AssetProviders should be able to configure which metadata they support (in similar way they can configure mediaTypes)
• Assets may then implement #supports(AssetMetadata) according to their own media-type (for media-type-dependent metadata), and Assets app should respect those dynamically. Should return Optional<AssetMetadata> by now.

Side note: Magnolia's DublinCore support effectively corresponds to the historic, limited and openly outdated DC Element Set 1.1 +/- a few arbitrary elements Tika 1.x judged universal enough.
Nowadays, DCMI encourages adoption of the DCMI Metadata Terms spec instead, and Tika 2.x slightly improves the split of metadata classes (for parser's extraction), but still doesn't fully embrace DC Metadata Terms.