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The delegation of the access may be specific and temporary (ie, allow someone to approve purchaes while I am on vacation) or may be permanent (I would like my administrative assistant to be able to act as my proxy.) The nature of the access is such that I cannot delegate more authority than I have myself, and I will still be held accountable for the actions taken on my behalf.
Solution
Proxy and delegation solutions are often application-specific. For example, in the faculty example above, the same application that is used to gather final grades would provide a user-interface for the faculty member to manage the delegation of grading.
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For the UM online directory, individuals can grant proxy access to any other member of the UM Community to manage directory attributes on their behalf. Proxy access is stored as an LDAP attribute on the in indivuidual directory entry.