Training Video:Virtual Fields
Walkthrough of adding a metadata field to a repository.
Virtual Meta Fields are fields that are not stored in the database, instead their input and output can be programmed. They can be used whenever a default displayed value is not what the user needs. Since their value is calculated their uses are limited by the one's imagination. Virtual Fields are not only limited to displaying some value, they can be used for setting values as well.
Except from Virtual Fields, this video touches other useful areas of EPrints as well, like how to write an EPrints script using the API, how fields are rendered, etc.