Reification

Reification is the process of giving a statement an identifier so that you can make statements about the statement.

For instance, you may have the statement "Britney loves Lance". Britney and Lance are obviously resources and "loves" is a predicate. This is a valid statement, at least in concept. (It would need to be formatted somewhat more formally to be a technically valid statement.) However, you may know it to be false. You could remove it from your database, but this would merely unassert it, not assert it to be false (cf. Open World Assumption). In order to make a statement about this statement, let's designate the statement "Britney loves Lance" as statement X.

Now we can happily say "X has-truth-value false". Suddenly we have a whole new level of expressiveness.