code: package it.unibz.inf.ontop.model.term;
  
  /*
   * #%L
   * ontop-obdalib-core
   * %%
   * Copyright (C) 2009 - 2014 Free University of Bozen-Bolzano
   * %%
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   * 
   *      http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   * #L%
   */
  
  import it.unibz.inf.ontop.model.type.TermType;
  
  import java.util.Optional;
  
  /**
   * This class defines a type of {@link ImmutableTerm} in which it has a constant
   * value.
   */
  public interface Constant extends NonFunctionalTerm, GroundTerm {
  
  	// TODO: eliminate getValue from this interface
  	String getValue();
  
  	/**
  	 * Empty if and only if is null.
  	 */
  	Optional<TermType> getOptionalType();
  
  	@Override
  	default boolean isDeterministic() {
  		return true;
  	}
  
  }
  