Sketching out what link-state addition would look like; quite easy until we get to the distributed store.
Added unit tests to provide durable-nondurable transitions.
FIxed issue where link could be accidentally activated.
Renamed parameter.

Change-Id: I8aa19a6583ec50dbf28769995f0a8ea9be9a4daa
diff --git a/core/api/src/main/java/org/onlab/onos/net/link/DefaultLinkDescription.java b/core/api/src/main/java/org/onlab/onos/net/link/DefaultLinkDescription.java
index fc3f335..986eb0a 100644
--- a/core/api/src/main/java/org/onlab/onos/net/link/DefaultLinkDescription.java
+++ b/core/api/src/main/java/org/onlab/onos/net/link/DefaultLinkDescription.java
@@ -34,9 +34,9 @@
     /**
      * Creates a link description using the supplied information.
      *
-     * @param src  link source
-     * @param dst  link destination
-     * @param type link type
+     * @param src         link source
+     * @param dst         link destination
+     * @param type        link type
      * @param annotations optional key/value annotations
      */
     public DefaultLinkDescription(ConnectPoint src, ConnectPoint dst,
@@ -64,9 +64,10 @@
 
     @Override
     public String toString() {
-        return MoreObjects.toStringHelper("Link").add("src", src())
-                                .add("dst", dst())
-                                .add("type", type()).toString();
+        return MoreObjects.toStringHelper(this)
+                .add("src", src())
+                .add("dst", dst())
+                .add("type", type()).toString();
     }
 
 }
diff --git a/core/api/src/main/java/org/onlab/onos/net/link/LinkDescription.java b/core/api/src/main/java/org/onlab/onos/net/link/LinkDescription.java
index 3343451..3078243 100644
--- a/core/api/src/main/java/org/onlab/onos/net/link/LinkDescription.java
+++ b/core/api/src/main/java/org/onlab/onos/net/link/LinkDescription.java
@@ -45,6 +45,5 @@
      */
     Link.Type type();
 
-
     // Add further link attributes
 }
diff --git a/core/api/src/main/java/org/onlab/onos/net/link/LinkEvent.java b/core/api/src/main/java/org/onlab/onos/net/link/LinkEvent.java
index b164b9e..763e95e 100644
--- a/core/api/src/main/java/org/onlab/onos/net/link/LinkEvent.java
+++ b/core/api/src/main/java/org/onlab/onos/net/link/LinkEvent.java
@@ -33,7 +33,7 @@
         LINK_ADDED,
 
         /**
-         * Signifies that a link has been updated.
+         * Signifies that a link has been updated or changed state.
          */
         LINK_UPDATED,
 
diff --git a/core/api/src/main/java/org/onlab/onos/net/link/LinkStore.java b/core/api/src/main/java/org/onlab/onos/net/link/LinkStore.java
index 95962e7..3af4f9f 100644
--- a/core/api/src/main/java/org/onlab/onos/net/link/LinkStore.java
+++ b/core/api/src/main/java/org/onlab/onos/net/link/LinkStore.java
@@ -95,6 +95,16 @@
                                         LinkDescription linkDescription);
 
     /**
+     * Removes the link, or marks it as inactive if the link is durable,
+     * based on the specified information.
+     *
+     * @param src link source
+     * @param dst link destination
+     * @return remove or update link event, or null if no change resulted
+     */
+    LinkEvent removeOrDownLink(ConnectPoint src, ConnectPoint dst);
+
+    /**
      * Removes the link based on the specified information.
      *
      * @param src link source
@@ -103,4 +113,5 @@
      */
     LinkEvent removeLink(ConnectPoint src, ConnectPoint dst);
 
+
 }