All keys are searchable, but only some are indexed. This means that searching by street address, for example, is possible, but it won't be nearly as fast as searching by name or e-mail address. I haven't put any non-indexed keys on this page.
In the LDAP data, I've used attributes that the University of Michigan uses in their own directory. A good rationale for the selection of attributes (keys) is one area for further research.
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Search full name:
Search last name: Sounds like
Search first name: Sounds like
Search email address:
Search department: