[ONOS-5084],[ONOS-5083] YANG schema registry for YMS

Change-Id: I88394307cb9be30237be0bb17e013d7af88a607c
diff --git a/apps/yms/app/src/main/java/org/onosproject/yms/app/ysr/DefaultYangModuleIdentifier.java b/apps/yms/app/src/main/java/org/onosproject/yms/app/ysr/DefaultYangModuleIdentifier.java
new file mode 100644
index 0000000..e98e982
--- /dev/null
+++ b/apps/yms/app/src/main/java/org/onosproject/yms/app/ysr/DefaultYangModuleIdentifier.java
@@ -0,0 +1,90 @@
+/*
+ * 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.yms.app.ysr;
+
+import org.onosproject.yms.ysr.YangModuleIdentifier;
+
+import java.util.Comparator;
+import java.util.Objects;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+
+/**
+ * Representation of default YANG module identifier.
+ */
+class DefaultYangModuleIdentifier implements YangModuleIdentifier,
+        Comparator<YangModuleIdentifier> {
+
+    private final String moduleName;
+    private final String revision;
+
+    /**
+     * Creates an instance of YANG module identifier.
+     *
+     * @param moduleName module's name
+     * @param revision   module's revision
+     */
+    DefaultYangModuleIdentifier(String moduleName, String revision) {
+        this.moduleName = moduleName;
+        this.revision = revision;
+    }
+
+    @Override
+    public String moduleName() {
+        return moduleName;
+    }
+
+    @Override
+    public String revision() {
+        return revision;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(moduleName, revision);
+    }
+
+    @Override
+    public int compare(YangModuleIdentifier id1, YangModuleIdentifier id2) {
+        int compare = id1.moduleName().compareTo(id2.moduleName());
+        if (compare != 0) {
+            return compare;
+        }
+        return id1.revision().compareTo(id2.revision());
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj instanceof DefaultYangModuleIdentifier) {
+            DefaultYangModuleIdentifier that = (DefaultYangModuleIdentifier) obj;
+            return Objects.equals(moduleName, that.moduleName) &&
+                    Objects.equals(revision, that.revision);
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(this)
+                .add("moduleName", moduleName)
+                .add("revision", revision)
+                .toString();
+    }
+}