Mapping RDF (subject, predicate, object) => (row, col, value) will result
in a (sparse) (n+1) x (m+1) matrix, where n is the number of (possibly
replicated) subjects (rows), and m is the number of (unique) predicates
(over all subjects).
ABCDEFGHIJKLMNOPQRSTUVWX
Copyright (c) 2011, iPlant Collaborative, University of Arizona, Cold Spring Harbor Laboratories, University of Texas at Austin.