References
The references, or identifiers, are extremely important in archival descriptions, and should be created with care. All references MUST BE UNIQUE within a repository.
There are two types of reference used for EAD descriptions. The EAD Editor uses the information you supply to populate both references, but they have different functions.
Description identifier: <eadid>
A required element of the header designating a unique code for the description of the collection or items being catalogued (not for the collection).
A unique reference for the described materials, displayed to the end-user. This is used to generate the Web identifier, or URI. Every level of description has its own unique reference.
Types of Reference: Current, Former, Alternative
You may require more than one reference. For example, if you have a former reference that you would like to display, or if you have an alternative reference, which may be the automated reference generated by your software. You can add these with the EAD Editor, or add them manually using the correct markup in the <unitid> entry.