Adding an initial API for the DomTree data structure.
Change-Id: I55da78c11f49c1e5843cfefbe0a5eed02c59498b
diff --git a/core/api/src/main/java/org/onosproject/store/service/DocumentTree.java b/core/api/src/main/java/org/onosproject/store/service/DocumentTree.java
new file mode 100644
index 0000000..5156c06
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+++ b/core/api/src/main/java/org/onosproject/store/service/DocumentTree.java
@@ -0,0 +1,97 @@
+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * 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.
+ */
+
+package org.onosproject.store.service;
+
+import org.onosproject.store.primitives.DocumentTreeNode;
+
+import java.util.Iterator;
+
+/**
+ * Interface for a tree with structure wherein keys hold information
+ * about the hierarchical structure of the tree (name of parent,
+ * grandparent etc.).
+ */
+public interface DocumentTree<V> {
+
+ /**
+ * Returns the root of the tree. This will be the first part of any fully
+ * qualified path and will enable discovery of the entire tree.
+ *
+ * @return a string that is the name of the root of the tree.
+ */
+ DocumentPath root();
+
+ /**
+ * Returns a sorted list containing all key value pairs that are direct
+ * descendants of the supplied parent. The returned list will be immutable.
+ * If the specified parent does not exist this method will fail with an
+ * exception.
+ *
+ * @throws NoSuchDocumentPathException if the parent does not exist
+ * @param parentPath the path to the parent of the desired nodes
+ * @return an iterator of the children of the specified parent
+ */
+ Iterator<DocumentTreeNode<V>> getChildren(DocumentPath parentPath);
+
+ /**
+ * Returns the value associated with the supplied key or null if no such
+ * node exists.
+ *
+ * @param key the key to query
+ * @return a value or null
+ */
+ DocumentTreeNode<V> getNode(DocumentPath key);
+
+ /**
+ * Takes a string that specifies the complete path to the mapping to be
+ * added or updated and creates the key value mapping or updates the value.
+ * If the specified parent cannot be found the operation fails with an
+ * error.
+ *
+ * @throws NoSuchDocumentPathException if the specified parent does not
+ * exist.
+ * @param key the fully qualified key of the entry to be added or updated
+ * @param value the non-null value to be associated with the key
+ * @return the previous mapping or null if there was no previous mapping
+ */
+ V putNode(DocumentPath key, V value);
+
+ /**
+ * Takes the fully qualified name of the node to be added along with
+ * the value to be added. If the specified key already exists it doesnot
+ * update anything & returns false. If the parent does not exist the
+ * operation fails with an exception.
+ *
+ * @throws NoSuchDocumentPathException if the specified parent does not
+ * exist.
+ * @param key the fully qualified key of the entry to be added or updated
+ * @param value the non-null value to be associated with the key
+ * @return returns true if the mapping could be added successfully
+ */
+ boolean createNode(DocumentPath key, V value);
+
+ /**
+ * Removes the node with the specified fully qualified key. Returns null if
+ * the node did not exist. This method will throw an exception if called on
+ * a non-leaf node.
+ *
+ * @throws IllegalDocumentModificationException if the node had children.
+ * @param key the fully qualified key of the node to be removed
+ * @return the previous value of the node or null if it did not exist
+ */
+ V removeNode(DocumentPath key);
+}