net.sf.kpex.prolog.Unfolder
For a given clause g= A0:-,A1,A2...,An, used as resolvent iterates over its possible unfoldings (LD-resolution steps) with clauses of the form B0:-B1,...,Bm in the default database. For each such step, a new clause (A0:-B1,...,Bm,A2...,An)mgu(A1,B0) is built and returned by the Unfolder's getElement method. Before the actual unfolding operations, builtins in Guard are executed, possibly providing bindings for some variables or failing. In case of failure of Guard or of unification, getElement() returns null.