This module defines the different types of terms...
Blank Node: http://www.w3.org/TR/rdf-concepts/#section-blank-nodes
“In non-persistent O-O software construction, support for object identity is almost accidental: in the simplest implementation, each object resides at a certain address, and a reference to the object uses that address, which serves as immutable object identity.
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Maintaining object identity in shared databases raises problems: every client that needs to create objects must obtain a unique identity for them; ” – Bertand Meyer