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Requester (req)
The Requester names the party making the request — typically a user or their institution — and conveys authorization context to the resolver.
The Requester is the person or agent on whose behalf services are requested, typically the user who clicked the link. In KEV form the prefix is req. It is optional, and at most one Requester may appear.
When a Requester is used
Most OpenURLs carry no Requester. The resolver already knows the institution (it is the institution's resolver), and the user's rights are established by IP range, single sign-on or a proxy session such as EZproxy. Where a Requester is sent, it is usually an identifier for the user or for an organisation acting on the user's behalf.
Examples
By identifier, using one of the registered URI schemes such as mailto:
req_id=mailto:jane.doe@example.eduBy reference, pointing at a directory entry, as in the XML example in the standard (which uses an LDAP URL and an eduPerson schema):
req_ref_fmt=http://my.example.org/eduperson.xsd
&req_ref=ldap://ldap.example.edu:389/janedBy-Value metadata for a Requester (req_val_fmt + req.*) is possible in principle, but the standard's initial Registry defines no Requester metadata format for scholarly use; the Request Transfer Message profile later registered its own XML Requester schema.
Privacy
A Requester can identify a person, so populating it has a privacy cost: the identifier ends up in resolver logs and possibly in referrer headers. Do not send personal identifiers unless the resolver genuinely needs them and the institution's privacy policy allows it.