Added graph-related utility code.
diff --git a/utils/misc/src/main/java/org/onlab/graph/EdgeWeight.java b/utils/misc/src/main/java/org/onlab/graph/EdgeWeight.java
new file mode 100644
index 0000000..b0630a0
--- /dev/null
+++ b/utils/misc/src/main/java/org/onlab/graph/EdgeWeight.java
@@ -0,0 +1,16 @@
+package org.onlab.graph;
+
+/**
+ * Abstraction of a graph edge weight function.
+ */
+public interface EdgeWeight<V extends Vertex, E extends Edge<V>> {
+
+ /**
+ * Returns the weight of the given edge as a unit-less number.
+ *
+ * @param edge edge to be weighed
+ * @return edge weight as a unit-less number
+ */
+ double weight(E edge);
+
+}