/*
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 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 *
 *   https://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
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 *   SPDX-License-Identifier: Apache-2.0
 */

package org.apache.jena.sparql.expr;

/**
 * Marker interface for a function that is "unstable".
 * That is, it isn't really a function.
 * <p>
 * A function returns the same result value when called with the same arguments.
 * Some "functions" do not obey this condition on functions; they look like functions but they aren't.
 * RAND, BNODE, UUID, STRUUID
 * <p>
 * There are also "functional forms" that have special evaluation rule. These return the same value when given the same arguments.
 * These are "stable".
 * <a href="https://www.w3.org/TR/sparql11-query/#func-forms"></a>
 */
public interface Unstable {}
