Identifier of a document within a publication that is (or contains) the target of the <related-object> element.
External Identifier: This element holds an external identifier assigned to a publication that is part of the description of a related object (<related-object>). The contents of this attribute should not be confused with the @id attribute, which holds an internal document identifier that can be used by software to preform a simple link.
| Value | Meaning |
|---|---|
| Text, numbers, or special characters | An identifier for the document that contains the related object (<related-object>). |
| Restriction: | |