define the last accessed date of an asset

In the asset details view, we expose a last accessed date.

In the book, the definition is not useful:

Last accessed

the date and time when the asset was last accessed

When and why this date changes is not well known.

If the date can be used as criteria to search on or as metadata for task operations, what it means needs to be well defined.

Expected

• document what this date means for assets stored in any repository format, blobstore, or repository
• confirm this date value adds product value and is backed by at least one use case

Possible use cases:

• when was this asset last viewed in the Browse or search feature of the UI
• should download attempts also update this date?

Out of scope:

• when was this asset last downloaded should defer to a distinct last download date