backward AND-branch unless we restrict the number of such backward AND-
branches and the number of partially derived relations in them.
Compiling
Unit Queries in
Recursive
IDDB
Recently, several research reports (Bancilhon and Ramakrishnan [1987]
Chang [1981], Henschen and Naqvi [1984], Han [1985]) showed that many
practical recursive axioms can be compiled into specific patterns of negative
clauses in recursive Horn databases. However, it seems very difficult to find
some regular patterns for the positive parts of non-Horn clauses in a recursive
IDDB,
in addition to the patterns for their negative parts.
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