From Wikipedia:

“A digital object identifier (or DOI) is a permanent identifier given to an electronic document, which is not related to its current location. A typical use of a DOI is to give a scientific paper or article a unique identifying number that can be used by anyone to locate details of the paper, and possibly an electronic copy. In this way it functions as a permalink. Unlike the URL system used on the Internet for web pages, the DOI does not change over time, even if the article is relocated (provided the DOI resolution system is updated when the change of location is made).”

So as long as you have the doi code which is is located within a document eg. “doi:10.1017/S1472669606001113”, you will be able to locate the document on the internet, regardless of whether it is moved to a new location.

To find the document in future simply put the doi number at the end of http://dx.doi.org/. Ie. http://dx.doi.org/10.1017/S1472669606001113 will direct you to the document, regardless of if it has been moved from it’s original location.

From Wikipedia:

“There are three main values granted by DOI adoption:

• Persistent Identification: each DOI unequivocally and permanently identifies the object to which it is associated
• Network Actionability: through Handle System technology, each DOI resolves to one or more web pages assigned by the publisher
• Semantic Interoperability: metadata allow to unambiguously communicate – to any user, from any place, at any point of the productive/distributive chain – all the pieces of information about the related objects and their hierarchical relationships”

http://en.wikipedia.org/wiki/Digital_object_identifier

http://www.doi.org/faq.html