+/*
+ * Copyright (c) 2017 Pantheon Technologies, s.r.o. and others. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.opendaylight.yangtools.yang.model.api;
+
+import com.google.common.annotations.Beta;
+import java.util.Optional;
+
+/**
+ * Mix-in interface for nodes which can be conditional on a when statement.
+ *
+ * @author Robert Varga
+ */
+@Beta
+public interface WhenConditionAware {
+ /**
+ * Returns when statement.
+ *
+ * <p>
+ * If when condition is present node defined by the parent data definition
+ * statement is only valid when the returned XPath
+ * expression conceptually evaluates to "true"
+ * for a particular instance, then the node defined by the parent data
+ * definition statement is valid; otherwise, it is not.
+ *
+ * @return XPath condition
+ */
+ Optional<RevisionAwareXPath> getWhenCondition();
+
+}