5.2. Key ? was(DESCRIPTION) when(DATE) resync This "metadata" command form provides nothing more than a way to carry a Key along with its description. The form is a "no-op" (except when "resync" is present) in the sense that the Key is treated as an adorned URL (as if no THUMP request were present). This form is designed as a passive data structrue that pairs a hyperlink with its metadata so that a formatted description might be surfaced by a client-side trigger event such as a "mouse-over". It is passive in the sense that selecting ("clicking on") the URL should result in ordinary access via the Key-as-pure-link as if no THUMP request were present. The form is effectively a metadata cache, and the DATE of last extraction tells how fresh it is. The "was" pseudo-command takes multiple arguments separated by "|", the first argument identifying the kind of DESCRIPTION that follows, e.g,

ARK systems such as Noid and N2T can record and provide metadata about any resource with an ARK.  That metadata becomes available via APIs, and can be seen when you add “?” to the end of an ARK URL. (See “Inflections” below) ARK metadata is very flexible, with no initial required metadata, but with support for multiple metadata schemas.  This flexibility is intentional: ARKs are designed to support a full digital object workflow, including the earliest stages before a resource is well-understood or described.

— interoperability with other data from other sources,