In case a referent is linked to several web resources - for example, if an article is available in PDF and in HTML versions then two web addresses (URLs) are provided - then a resource selection mechanism must be implemented by the Registration Agency (RA). It may be:
•a manual selection
When the user requests the referent's DOI name from the RA's application, the application generates a menu of options from which the user performs a manual choice.
•an automated selection
The URL to which the user is redirected is automatically selected among a list of provided addresses according to predefined rules that may be based on parameters depending on the user (for example, the user's geographic location which would be determined through their IP address).
The menu options or the redirection rules are retrieved from the DOI record. In particular, redirection rules can be defined through a redirection graph element containing XML code which can be interpreted by the DOI resolution service as illustrated below.
