Digital object identifier-is a string characters that are exclusively for identifying the electronic document or other object, goes to work. Metadata related to the object, associated with the name of the digital object identifier is stored, and the metadata can include a place, such as a web address (URL). where the object can be found in it. Digital object identifier for a document, etc. is permanent, whereas its location and other metadata can be changed. Refers to a document online, use the digital object identifier (DOI). than to refer to it with the web address (URL) will be, because if the URL is changed. the need is up, the publisher just metadata for the digital object identifier (DOI) in order to link to the address of the new web-to-day.