| 1 | package tuffy.ground; |
| 2 | |
| 3 | import java.util.ArrayList; |
| 4 | import java.util.HashMap; |
| 5 | import java.util.HashSet; |
| 6 | import java.util.Hashtable; |
| 7 | import java.util.Iterator; |
| 8 | |
| 9 | |
| 10 | import tuffy.mln.Atom; |
| 11 | import tuffy.mln.Clause; |
| 12 | import tuffy.mln.Literal; |
| 13 | import tuffy.mln.MarkovLogicNetwork; |
| 14 | import tuffy.mln.Predicate; |
| 15 | import tuffy.mln.Term; |
| 16 | import tuffy.mln.Tuple; |
| 17 | import tuffy.util.UIMan; |
| 18 | |
| 19 | /** |
| 20 | * "Syntactic" Knowledge Base Model Constructor. |
| 21 | * Analyze the query and the MLN rules to identify |
| 22 | * relevant atoms that need to be grounded to answer the query. |
| 23 | * Here KBMC only |
| 24 | * materialize relevant portion of predicate tables, while further refinement |
| 25 | * of active set of predicates and grounding |
| 26 | * of clauses are left to class {@link Grounding}. |
| 27 | */ |
| 28 | public class KBMC { |
| 29 | /** |
| 30 | * MLN used in this KBMC. |
| 31 | */ |
| 32 | private MarkovLogicNetwork mln; |
| 33 | |
| 34 | /** |
| 35 | * Constructor of KBMC. |
| 36 | * @param mln MLN used in this KBMC. |
| 37 | */ |
| 38 | public KBMC(MarkovLogicNetwork mln){ |
| 39 | this.mln = mln; |
| 40 | } |
| 41 | |
| 42 | public HashSet<Clause> allowedClauses = null; |
| 43 | |
| 44 | /** |
| 45 | * Run KBMC to identify and materialize relevant groundings of predicates. |
| 46 | * |
| 47 | * Here the relevant atoms needed to be grounded is determined as |
| 48 | * follows. One atom may be potentially relevant if it is in a clause $c$ |
| 49 | * that contains a literal $a$ that has the same predicate as another |
| 50 | * potentially relevant tuple $b$. If $a$ and this predicate $b$ |
| 51 | * has MGU $m$, substituting this atom with $m$ will obtain tuple that |
| 52 | * is potentially relevant. Recursively do this until no potentially |
| 53 | * relevant tuples are generated according current set of potentially |
| 54 | * relevant tuples. Here $m$'s role is providing restrictions on possible |
| 55 | * groundings. |
| 56 | * |
| 57 | * Only ground a set of tuples, s.t., 1) $\forall$ tuple $a$, $b$ in this |
| 58 | * set, $a$ does not subsume $b$; and 2) $\forall$ tuple $c$ that is |
| 59 | * potentially relevant, there exists tuple $a$ in this set, that $a$ |
| 60 | * subsumes $c$. |
| 61 | * |
| 62 | * Note that, grounding both $a$ and $b$ when $a$ subsumes $b$ is not |
| 63 | * necessary, because the grounding results of $a$ will include $b$. |
| 64 | * |
| 65 | */ |
| 66 | public void run() { |
| 67 | // atoms to be explored |
| 68 | Hashtable<Predicate, AtomCutSet> toExp = new |
| 69 | Hashtable<Predicate, AtomCutSet>(); |
| 70 | // atoms deemed relevant |
| 71 | Hashtable<Predicate, AtomCutSet> relAtoms = new |
| 72 | Hashtable<Predicate, AtomCutSet>(); |
| 73 | UIMan.verbose(1, ">>> KBMC: Identifying relevant atoms/clauses..."); |
| 74 | // begin with queries |
| 75 | for(Predicate qp : mln.getAllPred()) { |
| 76 | AtomCutSet q = new AtomCutSet(qp); |
| 77 | if(qp.hasQuery()) { |
| 78 | for(Atom a : qp.getQueryAtoms()) { |
| 79 | q.addTuple(a.args); |
| 80 | //System.out.println(a); |
| 81 | } |
| 82 | } |
| 83 | toExp.put(qp, q); |
| 84 | |
| 85 | relAtoms.put(qp, new AtomCutSet(qp)); |
| 86 | } |
| 87 | bigloop: |
| 88 | while(true) { |
| 89 | // pick next seed |
| 90 | Predicate pred = null; |
| 91 | Tuple seed = null; |
| 92 | for(AtomCutSet aset : toExp.values()) { |
| 93 | seed = aset.top(); |
| 94 | if(seed != null) { |
| 95 | pred = aset.pred; |
| 96 | break; |
| 97 | } |
| 98 | } |
| 99 | // check if seeds have been exhausted |
| 100 | if(seed == null) break; |
| 101 | //System.out.println("SEED - " + pred.getName() + seed); |
| 102 | |
| 103 | // search |
| 104 | for(Clause c : pred.getRelatedClauses()) { |
| 105 | |
| 106 | if(allowedClauses != null && !allowedClauses.contains(c)){ |
| 107 | continue; |
| 108 | } |
| 109 | |
| 110 | //System.out.println("CLAUSE - " + c); |
| 111 | mln.setClauseAsRelevant(c); |
| 112 | for(Literal lit : c.getLiteralsOfPredicate(pred)) { |
| 113 | if(lit.isBuiltIn()) continue; |
| 114 | // calc mgu |
| 115 | HashMap<String, Term> vmap = lit.mostGeneralUnification(seed); |
| 116 | if(vmap == null) continue; |
| 117 | // apply to other literals |
| 118 | for(Literal ol : c.getRegLiterals()) { |
| 119 | if(ol.isBuiltIn()) continue; |
| 120 | if(ol.equals(lit)) continue; |
| 121 | Literal sol = ol.substitute(vmap); |
| 122 | Tuple newa = sol.toTuple(); |
| 123 | Predicate newp = sol.getPred(); |
| 124 | if(newp.noNeedToGround()) continue; |
| 125 | if(toExp.get(newp).subsumes(newa) || |
| 126 | relAtoms.get(newp).subsumes(newa)) { |
| 127 | continue; |
| 128 | } |
| 129 | //System.out.println("GOT " + newp.name + newa); |
| 130 | toExp.get(newp).addTuple(newa); |
| 131 | // short cut |
| 132 | if(newp.equals(pred) && !toExp.get(pred).contains(seed)) { |
| 133 | continue bigloop; |
| 134 | } |
| 135 | } |
| 136 | |
| 137 | } |
| 138 | } |
| 139 | toExp.get(pred).removeTuple(seed); |
| 140 | relAtoms.get(pred).addTuple(seed); |
| 141 | } |
| 142 | // fill up tables |
| 143 | UIMan.verbose(1, ">>> KBMC: Materializing predicates..."); |
| 144 | for(AtomCutSet as : relAtoms.values()) { |
| 145 | Predicate p = as.pred; |
| 146 | |
| 147 | if(mln.isScoped(p) || p.noNeedToGround()) continue; |
| 148 | boolean suc = as.collectAll(); |
| 149 | if(suc) { |
| 150 | for(Tuple t : as.heap) { |
| 151 | Atom a = new Atom(p, t); |
| 152 | if(a.pred.isClosedWorld()){ |
| 153 | a.truth = false; |
| 154 | a.type = Atom.AtomType.EVIDENCE; |
| 155 | } |
| 156 | UIMan.verbose(1, " " + a.toString() + " - " + UIMan.comma(a.groundSize()) + " tuples"); |
| 157 | p.groundAndStoreAtom(a); |
| 158 | } |
| 159 | } |
| 160 | } |
| 161 | } |
| 162 | |
| 163 | /** |
| 164 | * AtomCutSet is set of atoms with the same predicate. |
| 165 | * These atoms are organized in strata, with each stratum |
| 166 | * responds to a different degree-of-freedom. Atoms in a AtomCutSet |
| 167 | * satisfy that $\forall$ atom $a$ in this set, there does not exist atom $b$ |
| 168 | * in this set that $a$ subsumes $b$. For the definition of ``subsume'', see |
| 169 | * {@link Tuple#subsumes(Tuple)}. |
| 170 | * |
| 171 | */ |
| 172 | private static class AtomCutSet { |
| 173 | /** |
| 174 | * Predicate of this AtomCutSet. |
| 175 | */ |
| 176 | Predicate pred; |
| 177 | |
| 178 | /** |
| 179 | * Arity of {@link AtomCutSet#pred}. |
| 180 | */ |
| 181 | int arity; |
| 182 | |
| 183 | /** |
| 184 | * Whether this AtomCutSet is complete. Here by ``complete'' |
| 185 | * it means arbitrary tuple is subsumed by some tuples in this |
| 186 | * AtomCutSet. For the definition of ``subsume'', see |
| 187 | * {@link Tuple#subsumes(Tuple)}. |
| 188 | */ |
| 189 | boolean complete = false; |
| 190 | |
| 191 | /** |
| 192 | * List of stratum in this AtomCutSet. |
| 193 | */ |
| 194 | ArrayList<Stratum> strata = new ArrayList<Stratum>(); |
| 195 | |
| 196 | /** |
| 197 | * Set of all tuples in each stratum. |
| 198 | */ |
| 199 | HashSet<Tuple> heap = new HashSet<Tuple>(); |
| 200 | |
| 201 | /** |
| 202 | * Copy all tuples in each stratum to {@link AtomCutSet#heap}. |
| 203 | * @return true if some of this stratum is not empty. |
| 204 | */ |
| 205 | public boolean collectAll() { |
| 206 | for(Stratum s : strata) { |
| 207 | heap.addAll(s.tuples); |
| 208 | } |
| 209 | return (!heap.isEmpty()); |
| 210 | } |
| 211 | |
| 212 | /** |
| 213 | * Constructor of AtomCutSet. Given a predicate, |
| 214 | * initialize a stratum for each number between |
| 215 | * 0 and this predicate's arity. Each stratum |
| 216 | * for number $n$ means tuples in this stratum |
| 217 | * have degree-of-freedom $n$. |
| 218 | * @param p |
| 219 | */ |
| 220 | public AtomCutSet(Predicate p) { |
| 221 | pred = p; |
| 222 | arity = p.arity(); |
| 223 | for(int i=0; i<=p.arity(); i++) { |
| 224 | strata.add(new Stratum()); |
| 225 | } |
| 226 | } |
| 227 | |
| 228 | /** |
| 229 | * Returns the first tuple in the first stratum. |
| 230 | */ |
| 231 | public Tuple top() { |
| 232 | for(int i=arity; i>=0; i--) { |
| 233 | Stratum s = strata.get(i); |
| 234 | if(!s.isEmpty()) { |
| 235 | return s.tuples.iterator().next(); |
| 236 | } |
| 237 | } |
| 238 | return null; |
| 239 | } |
| 240 | |
| 241 | /** |
| 242 | * Remove the input tuple from corresponding stratum. Here |
| 243 | * the corresponding stratum is found by the degree-of-freedom |
| 244 | * of the input tuple. |
| 245 | * @param t input tuple. |
| 246 | */ |
| 247 | public void removeTuple(Tuple t) { |
| 248 | strata.get(t.dimension).tuples.remove(t); |
| 249 | } |
| 250 | |
| 251 | /** |
| 252 | * Return true if the input tuple is in the corresponding stratum. |
| 253 | * Here the corresponding stratum is found by the degree-of-freedom |
| 254 | * of input tuple. |
| 255 | * @param t input tuple. |
| 256 | */ |
| 257 | public boolean contains(Tuple t) { |
| 258 | return strata.get(t.dimension).tuples.contains(t); |
| 259 | } |
| 260 | |
| 261 | |
| 262 | /** |
| 263 | * Returns true if there exists a tuple in this AtomCutSet |
| 264 | * that subsumes the input tuple. For the definition of ``subsume'', see |
| 265 | * {@link Tuple#subsumes(Tuple)}. |
| 266 | * @param t input tuple. |
| 267 | */ |
| 268 | public boolean subsumes(Tuple t) { |
| 269 | int dim = t.dimension; |
| 270 | if(complete) return true; |
| 271 | if(dim == arity) { |
| 272 | return false; |
| 273 | } |
| 274 | for(int i=arity; i>= dim; i--) { |
| 275 | if(strata.get(i).subsumes(t)) return true; |
| 276 | } |
| 277 | return false; |
| 278 | } |
| 279 | |
| 280 | /** |
| 281 | * Add a tuple to corresponding stratum. Remove all the |
| 282 | * existing tuples that can be subsumed by the new input |
| 283 | * tuple. The goal is $\forall$ tuples $a$ and $b$ in |
| 284 | * a certain stratum, $a$ does not subsume $b$. This function |
| 285 | * pluses a condition in {@link KBMC#run()} ensure this. |
| 286 | * |
| 287 | * @param t input tuple |
| 288 | */ |
| 289 | public void addTuple(Tuple t) { |
| 290 | int dim = t.dimension; |
| 291 | if(dim == arity) { |
| 292 | for(Stratum s : strata) { |
| 293 | s.clear(); |
| 294 | } |
| 295 | strata.get(dim).add(t); |
| 296 | complete = true; |
| 297 | return ; |
| 298 | } |
| 299 | strata.get(dim).add(t); |
| 300 | for(int i=dim-1; i>=0; i--) { |
| 301 | strata.get(i).removeTuplesSubsumedBy(t); |
| 302 | } |
| 303 | } |
| 304 | |
| 305 | /** |
| 306 | * A stratum is a set of tuples with the same degree-of-freedom. |
| 307 | */ |
| 308 | class Stratum{ |
| 309 | /** |
| 310 | * Set of tuples in this stratum. |
| 311 | */ |
| 312 | HashSet<Tuple> tuples = new HashSet<Tuple>(); |
| 313 | |
| 314 | /** |
| 315 | * Add a tuple to this stratum. |
| 316 | * @param t Added tuple. |
| 317 | */ |
| 318 | public void add(Tuple t) { |
| 319 | tuples.add(t); |
| 320 | } |
| 321 | |
| 322 | /** |
| 323 | * Test whether there is a tuple in this stratum |
| 324 | * subsumes the input tuple. For the definition of |
| 325 | * ``subsume'', see {@link Tuple#subsumes(Tuple)}. |
| 326 | * @param t tuple to be tested. |
| 327 | * @return true if there is a tuple subsumes the input tuple. |
| 328 | */ |
| 329 | public boolean subsumes(Tuple t) { |
| 330 | for(Tuple at : tuples) { |
| 331 | if(at.subsumes(t)) return true; |
| 332 | } |
| 333 | return false; |
| 334 | } |
| 335 | |
| 336 | /** |
| 337 | * Remove tuples in this stratum that subsumes the input tuple. |
| 338 | * |
| 339 | * @param t input tuple. |
| 340 | * @see Stratum#subsumes(Tuple). |
| 341 | */ |
| 342 | public void removeTuplesSubsumedBy(Tuple t) { |
| 343 | for(Iterator<Tuple> it = tuples.iterator(); it.hasNext();) { |
| 344 | if(t.subsumes(it.next())) { |
| 345 | it.remove(); |
| 346 | } |
| 347 | } |
| 348 | } |
| 349 | |
| 350 | /** |
| 351 | * Return true if this stratum is empty. |
| 352 | */ |
| 353 | public boolean isEmpty() { |
| 354 | return tuples.isEmpty(); |
| 355 | } |
| 356 | |
| 357 | /** |
| 358 | * Empty this stratum. |
| 359 | */ |
| 360 | public void clear() { |
| 361 | tuples.clear(); |
| 362 | } |
| 363 | } |
| 364 | } |
| 365 | |
| 366 | } |