resolutioninferenceengine.java

Mandarax是一个规则引擎的纯Java实现。它支持多类型的事实和基于反映的规则

		}
		catch (ClauseSetException x) {
			String msg = "Exception getting clause iterator for " + goal;
			LOG_IE_STEP.error(msg,x);
			if (session.getExceptionHandlingStrategy()==BUBBLE_EXCEPTIONS) throw new InferenceException(msg,x);
		}

		if((nextNode == null) || nextNode.isFailed ()) {
			node.setFailed (true);
		}

		return node;
	}
	/**
	 * Answer a query, retrieve (multiple different) result.
	 * The cardinality contraints describe how many results should be computed. It is either
	 * <ol>
	 * <li> <code>ONE</code> - indicating that only one answer is expected
	 * <li> <code>ALL</code> - indicating that all answers should be computed
	 * <li> <code>an integer value greater than 0 indicating that this number of results expected
	 * </ol>
	 * This inference engines does not support retrieving multiple answers!
	 * If requested, a runtime exception (<code>java.lang.IllegalArgumentException</code>)
	 * is thrown indicating that the parameter (e.g. <code>ALL</code>) is not valid.
	 * @see #ONE
	 * @see #ALL
	 * @return the result set of the query
	 * @param query the query
	 * @param kb the knowledge base used to answer the query
	 * @param aCardinalityConstraint the number of results expected
	 * @param exceptionHandlingPolicy one of the constants definied in this class (BUBBLE_EXCEPTIONS,TRY_NEXT)
	 * @throws an InferenceException
	 */
	public ResultSet query(final Query query, org.mandarax.kernel.KnowledgeBase kb,int aCardinalityConstraint,int exceptionHandlingPolicy) throws InferenceException {
		final Clause firstGoal = getGoal(query);
		VariableRenaming renameVariables = new VariableRenaming ();
		DerivationNodeImpl   linResult =  proof (firstGoal, new ArrayList (), new DerivationStepCounter(), renameVariables, LOG_IE_STEP.isDebugEnabled (), new ArrayList (MAXSTEPS),new SessionImpl(kb,this,query,exceptionHandlingPolicy,InferenceEngine.ONE));
		linResult.setSemanticEvaluationPolicy(getSemanticEvaluationPolicy());
		Replacement[]  replacements = IEUtils.getReplacements (linResult, firstGoal);
		DerivationNodeImpl root = derivationTreeBuilder.buildTree (linResult);
		final Result result = root.isFailed()?null:new Result (new Derivation (root,0), replacements);   
		ResultSet rs = new ResultSet() {
				private int pos = -1;
				private List vars = null;
				/**
	 			* Moves the cursor to the first row in this ResultSet object.
	 			* @return true if the cursor is on a valid row; false if there are no rows in the result set
	 			*/
				public boolean first() {
					pos = 0;
					return result!=null;
				}
				/**
				 * Moves the cursor to the last row in this ResultSet object.
				 * @return true if the cursor is on a valid row; false if there are no rows in the result s
				 */
				public boolean last() {
					pos = 0;
					return result!=null;	
				}
				/**
				 * Retrieves the current result number. Numbering starts with 1.
				 * @return a number
				 */
				public int getResultNumber() {return pos==0?1:-1;}
				/**
				 * Moves the cursor down one row from its current position. A ResultSet cursor is initially positioned 
				 * before the first row; the first call to the method next makes the first row the current row; 
				 * the second call makes the second row the current row, and so on. 
				 * @return true if the new current row is valid; false if there are no more rows
				 */
				public boolean next() {	
					pos=pos+1;
					return result!=null && pos==0;	
				}
				/**
				 * Moves the cursor to the previous row in this ResultSet object. 
				 * @return true if the cursor is on a valid row; false if it is off the result set
				 */
				public boolean previous() {
					return false; 
				};
				/**
	 			 * Get the current position of the cursor.
	 			 * @return an integer
	 			 */
				public int getCursorPosition() {
					return pos;
				}				
				/**
				 * Releases this ResultSet resources.
				 */
				public void close() {}   
				/**
				 * Get the derivation of the current result.
				 * Throw an exception if the cursor is not positioned at a result.
				 * @return the proof (derivation)
				 */
				public Derivation getProof() throws InferenceException {
					if (pos!=0) throw new InferenceException("Illegal cursor position " + pos + " in result set.");
					return result.getProof();
				}
				/**
				 * Get the object that replaces the variable with the given name and type.
				 * If there is no such object, return null.
				 * Throw an exception if the cursor is not positioned at a result.
				 * @return the object that replaced the variable
				 * @param type the type of the variable
				 * @param name the name of the variable
				 * @exception an inference exception 
				 */
				public Object getResult(Class type, String name) throws InferenceException {
					if (pos!=0) throw new InferenceException("Illegal cursor position " + pos + " in result set.");
					return result.getResult(type,name);
				}
				/**
				 * Get the object that replaces the variable.
				 * If there is no such object, return null.
				 * Throw an exception if the cursor is not positioned at a result.
				 * @return the object that replaced the variable
				 * @param term the variable term that is (perhaps) replaced
				 * @exception an inference exception 
				 */
				public Object getResult(VariableTerm term)throws InferenceException {
					if (pos!=0) throw new InferenceException("Illegal cursor position " + pos + " in result set.");
					return result.getResult(term);
				}
				/**
				 * Get a list of all variable terms in the query.
				 * @return a list of variable terms
				 */
				public List getQueryVariables() {
					if (vars == null) vars = IEUtils.getVars(firstGoal);
					return vars;
				}
				/**
				 * Indicates whether the cursor is at the first position.
				 * @return a boolean
				 */
				public boolean isFirst() {
					return result!=null && pos==0;
				}
				/**
				 * Indicates whether the cursor is at the last position.
				 * @return a boolean
				 */
				public boolean isLast() {
					return result!=null && pos==0;
				}

				/**
				 * Moves the cursor a relative number of results, either positive or negative.
				 * @param offset the number of results
				 * @return true if the cursor is on the result set; false otherwise.
				 */
				public boolean relative(int offset) {
					pos = pos+offset;
					return pos==0;
				}
				/**
				 * Moves the cursor to the given result number.
				 * @param resultNo the number of results.
				 * @return true if the cursor is on the result set; false otherwise
				 */
				public boolean absolute(int resultNo) {
					pos = resultNo-1; // like in JDBC - the number of the first result is 1, not 0 !
					return pos==0; 
				}
				/**
				 * Moves the cursor to the front of this ResultSet object, just before the first row. 
				 * This method has no effect if the result set contains no rows.
				 */
				public void beforeFirst() {
					pos = -1;
				}
	
				/**
				 * Moves the cursor to the end of this ResultSet object, just after the last row. 
				 * This method has no effect if the result set contains no rows.
				 */
				public void afterLast() {
					pos = 2;
				}
				/**
				 * Retrieves whether the cursor is before the first row in this ResultSet object.
				 * @return true if the cursor is before the first row; false if the cursor is at any other position or the result set contains no rows
				 */
				public boolean isBeforeFirst() throws InferenceException {
					return pos==-1;
				}
	
				/**
				 * Retrieves whether the cursor is after the last result in this ResultSet object.
				 * @return true if the cursor is after the last result; false if the cursor is at any other position or the result set contains no results
				 */
				public boolean isAfterLast() throws InferenceException {
					return pos==2;
				}
				/**
				 * Get the results as map.
				 * @return a map
				 */
				public Map getResults() throws InferenceException {
					if (pos!=0) throw new InferenceException("Illegal cursor position " + pos + " in result set.");
					return result.getResults();
				}
				
		
		};
		return rs;
	
	}
}