001    package aima.logic.fol.inference.proof;
002    
003    import java.util.List;
004    
005    /**
006     * @author Ciaran O'Reilly
007     * 
008     */
009    public abstract class AbstractProofStep implements ProofStep {
010            private int step = 0;
011    
012            public AbstractProofStep() {
013    
014            }
015    
016            //
017            // START-ProofStep
018            public int getStepNumber() {
019                    return step;
020            }
021    
022            public void setStepNumber(int step) {
023                    this.step = step;
024            }
025            
026            public abstract List<ProofStep> getPredecessorSteps();
027    
028            public abstract String getProof();
029    
030            public abstract String getJustification();
031    
032            // END-ProofStep
033            //
034    }