What constitutes an “institution,” for purposes of the Registry?
That is largely up to the community that utilizes the WorldCat Registry. OCLC has pre-populated the Registry with entries for libraries, archives, museums and other forms of institutions. Traditionally, of course, institutions consist of physical facilities with physical and/or electronic collections and/or services that cross multiple departments or branches, administered by one or more professionals. However, no restrictions prevent a smaller physical entity such as a church library, or a “virtual” entity such as a digital library, from representing itself in the Registry. Note, though, that a postal address is required.