The level of granularity of the identifier will be defined by whatever the publisher chooses to publish as a separate item and present to the national library for deposit. The deposited item is what the national library will have to record in the national bibliography and preserve in its deposit. If a publisher presents a monograph to the national library, the monograph should have an unique identifier and if a publisher presents an article as a separate document, the article should have an unique identifier. A general problem with Internet publications is that their location tends to change. Documents move from one location to another whenever this is convenient for the document owner.
Users consequently have problems in retrieving the document.
In order to solve these problems initiatives have been taken in the Internet community to develop a persistent identifier for documents. In order to evaluate existing identification schemes a set of requirements has been drawn up. Standard Recognised as a standard by international bodies or a proposed standard that is likely to become a recognised standard in the near future. Global uniqueness There should be a guarantee that identifiers will not be used for more than one item. The identifier must be unique for every specific form of a document.