Embodiments of the present invention provide methods and apparatuses for providing unique smart identifiers for entities of various entity types, such as documents or portions thereof. Each smart identifier comprises one or more data values provided by a requester of the smart identifier, or data values derived there from. The generation may be entity type based and/or customized. Embodiments include registration of custom smart identifier generation functions, with particular parameter data value requirements for particular entity types. Embodiments include smart identifier requesters inquiring about, and receiving answers to parameter data values required to generate smart identifiers for entities of various entity types.