CASC-JC Entrants' Sample Solutions

## EP 0.8

S. Schulz
Institut für Informatik, Technische Universität München, Germany, and RISC-Linz, Johannes Kepler Universität Linz, Austria
schulz@informatik.tu-muenchen.de

Here is a list of all inferences:

er
  Equality resolution: x!=a v x=x ==> a=a
pm
  Paramodulation. Note that E considers all literals as equational, and thus also performs resolution by a combination of top-level paramodulation and clause normalization.
ef
  Equality factoring (factor equations on one side only, move the remaining disequation into the precondition): x=a v b=c v x=d ==> a!=c v b=c vb=d
split
  Clause splitting a la Vampire (non-deductive, but maintains unsatisfiability)
rw
  Rewriting, each rw-expression corresponds to exacly one rewrite step with the named clause. This is also used for equational unfolding.
sr
  Simplify-reflect: An (equational) version of unit-cutting. As as example, see this positive simplify-reflect step: [a=b], [f(a)!=f(b)] => [].
ar
  AC-resolution: Delete literals that are trivial modulo the AC-theory induced by the named clauses
cn
  Clause normalize, delete trivial and repeated literals

The first proof uses all but "ef", although it uses some in fairly trivial ways. Note that clause normalization is inherently performed after all inferences but rewriting. The second is the required proof for SYN075-1, and contains an example for "ef".

ALL_RULES

    # Problem is unsatisfiable, constructing proof object
    # TSTP exit status: Unsatisfiable
    # Proof object starts here.
         1 : [++equal(f(X1,X2), f(X2,X1))] : initial
         2 : [++equal(f(X1,f(X2,X3)), f(f(X1,X2),X3))] : initial
         3 : [++equal(g(X1,X2), g(X2,X1))] : initial
         4 : [--equal(f(f(X1,X2),f(X3,g(X4,X5))), f(f(g(X4,X5),X3),f(X2,X1))),--equal(k(X1,X1), k(a,b))] : initial
         5 : [++equal(b, c),--equal(X1, X2),--equal(X3, X4),--equal(c, d)] : initial
         6 : [++equal(a, b),++equal(a, c)] : initial
         7 : [++equal(i(X1), i(X2))] : initial
         8 : [++equal(c, d),--equal(h(i(a)), h(i(e)))] : initial
        13 : [--equal(k(a,b), k(X1,X1))] : ar(4,1,3,2)
        23 : [++equal(c, b),++epred1_0,--equal(d, c),--equal(X3, X4)] : split(5)
        24 : [++epred2_0,--equal(X1, X2)] : split(5)
        25 : [--epred2_0,--epred1_0] : split(5)
        26 : [++epred2_0] : er(24)
        27 : [--$true,--epred1_0] : rw(25,26)
        28 : [++equal(c, b),++epred1_0,--equal(d, c)] : er(23)
        29 : [++equal(c, b),--equal(d, c)] : sr(28,27)
        30 : [++equal(d, c)] : sr(8,7)
        31 : [++equal(c, b),--equal(c, c)] : rw(29,30)
        32 : [++equal(c, b)] : cn(31)
        34 : [++equal(b, a)] : pm(6,32)
        35 : [--equal(k(b,b), k(X1,X1))] : rw(13,34)
       120 : [] : er(35)
       121 : [] : 120 : "proof"
    # Proof object ends here.

SYN075-1

    # Problem is unsatisfiable, constructing proof object
    # TSTP exit status: Unsatisfiable
    # Proof object starts here.
         1 : [++equal(X1, a),--big_f(X1,X2)] : initial
         3 : [++big_f(X1,X2),--equal(X1, a),--equal(X2, b)] : initial
         4 : [++equal(f(X2), X2),--big_f(X1,f(X2)),--equal(X1, g(X2))] : initial
         6 : [++big_f(X1,f(X2)),++equal(f(X2), X2),--equal(X1, g(X2))] : initial
         9 : [++big_f(h(X1,X2),f(X1)),++equal(h(X1,X2), X2),--equal(f(X1), X1)] : initial
        10 : [--equal(f(X1), X1),--equal(h(X1,X2), X2),--big_f(h(X1,X2),f(X1))] : initial
        18 : [++equal(f(X2), X2),--equal(g(X2), X1)] : pm(4,6)
        19 : [++equal(f(X1), X1)] : er(18)
        24 : [--equal(X1, X1),--equal(h(X1,X2), X2),--big_f(h(X1,X2),f(X1))] : rw(10,19)
        25 : [--equal(X1, X1),--equal(h(X1,X2), X2),--big_f(h(X1,X2),X1)] : rw(24,19)
        26 : [--equal(h(X1,X2), X2),--big_f(h(X1,X2),X1)] : cn(25)
        27 : [++equal(h(X1,X2), X2),++big_f(h(X1,X2),X1),--equal(f(X1), X1)] : rw(9,19)
        28 : [++equal(h(X1,X2), X2),++big_f(h(X1,X2),X1),--equal(X1, X1)] : rw(27,19)
        29 : [++equal(h(X1,X2), X2),++big_f(h(X1,X2),X1)] : cn(28)
        30 : [++equal(a, h(X1,X2)),++equal(h(X1,X2), X2)] : pm(1,29)
        36 : [++equal(h(X1,X2), X2),--equal(a, X2)] : ef(30)
        46 : [--big_f(X2,X1),--equal(h(X1,X2), X2),--equal(a, X2)] : pm(26,36)
        56 : [--big_f(X2,X1),--equal(a, X2)] : pm(46,36)
        63 : [--equal(a, X1),--equal(b, X2)] : pm(56,3)
        94 : [--equal(b, X1)] : er(63)
       103 : [] : er(94)
       104 : [] : 103 : "proof"
    # Proof object ends here.