Added a set of abstractions for flow rule subsystem.
Added an apps source subtree.
diff --git a/core/api/src/main/java/org/onlab/onos/net/flow/Criteria.java b/core/api/src/main/java/org/onlab/onos/net/flow/Criteria.java
new file mode 100644
index 0000000..9595797
--- /dev/null
+++ b/core/api/src/main/java/org/onlab/onos/net/flow/Criteria.java
@@ -0,0 +1,25 @@
+package org.onlab.onos.net.flow;
+
+/**
+ * Factory class to create various traffic selection criteria.
+ */
+public final class Criteria {
+
+ // Ban construction
+ private Criteria() {
+ }
+
+ /**
+ * Creates a match on ETH_SRC field using the specified value. This value
+ * may be a wildcard mask.
+ *
+ * @param macValue MAC address value or wildcard mask
+ * @return match criterion
+ */
+ public static Criterion matchEthSrc(MACValue macValue) {
+ return null;
+ }
+
+ // Dummy to illustrate the concept for now; delete ASAP
+ private static class MACValue { }
+}