[ONOS-2408]Data model and utility class about RFC 7047 (ovsdb protocol).
The whole lib of ovsdb provides the function of encode to jasonRPC and
decode to Pojo to consumer, the bussiness of coordination of
communication is implemented by adapter.

Change-Id: I4c35426273394c1699207e5a4f2e98cead59f1e1
diff --git a/ovsdb/rfc/src/main/java/org/onosproject/ovsdb/rfc/schema/type/KeyValuedColumnType.java b/ovsdb/rfc/src/main/java/org/onosproject/ovsdb/rfc/schema/type/KeyValuedColumnType.java
new file mode 100644
index 0000000..2419cdd
--- /dev/null
+++ b/ovsdb/rfc/src/main/java/org/onosproject/ovsdb/rfc/schema/type/KeyValuedColumnType.java
@@ -0,0 +1,108 @@
+/*
+ * Copyright 2015 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.ovsdb.rfc.schema.type;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.Objects;
+
+/**
+ * a JSON object that describes the type of a database column, with key and
+ * value. Refer to RFC 7047 Section 3.2.
+ */
+public final class KeyValuedColumnType implements ColumnType {
+    private final BaseType keyType;
+    private final BaseType valueType;
+    private final int min;
+    private final int max;
+
+    /**
+     * Constructs a KeyValuedColumnType object.
+     * @param keyType BaseType entity
+     * @param valueType BaseType entity
+     * @param min min constraint
+     * @param max max constraint
+     */
+    public KeyValuedColumnType(BaseType keyType, BaseType valueType, int min,
+                               int max) {
+        checkNotNull(keyType, "keyType is not null");
+        checkNotNull(valueType, "valueType is not null");
+        this.keyType = keyType;
+        this.valueType = valueType;
+        this.min = min;
+        this.max = max;
+    }
+
+    /**
+     * Get keyType.
+     * @return keyType
+     */
+    public BaseType keyType() {
+        return keyType;
+    }
+
+    /**
+     * Get valueType.
+     * @return valueType
+     */
+    public BaseType valueType() {
+        return valueType;
+    }
+
+    /**
+     * Get min.
+     * @return min
+     */
+    public int min() {
+        return min;
+    }
+
+    /**
+     * Get max.
+     * @return max
+     */
+    public int max() {
+        return max;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(keyType, valueType, min, max);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj instanceof KeyValuedColumnType) {
+            final KeyValuedColumnType other = (KeyValuedColumnType) obj;
+            return Objects.equals(this.keyType, other.keyType)
+                    && Objects.equals(this.valueType, other.valueType)
+                    && Objects.equals(this.min, other.min)
+                    && Objects.equals(this.max, other.max);
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(this).add("keyType", keyType)
+                .add("valueType", valueType).add("min", min).add("max", max)
+                .toString();
+    }
+}