diff --git a/schema/cord-service-vsg.yang b/schema/cord-service-vsg.yang
index aeae976..16615e8 100644
--- a/schema/cord-service-vsg.yang
+++ b/schema/cord-service-vsg.yang
@@ -31,14 +31,15 @@
       "This grouping represents a VSG agent/provider which manages multiple
        VSG gateways. The VSG agent provides agregate abstraction of
        the entire NFaaS as a single switch to the controller. Each
-       port entry of the agent represents each VSG endpoint as a
-       separate openflow port.";
+       port entry of the agent represents each VSG subscriber flow as
+       a separate openflow port.";
 
     list gateway {
       description
         "Each entry represents a VSG instance managed by the agent.";
 
-      leaf id { type yang:uuid; }
+      leaf id { type xos:unique-identifier; }
+      
       container services {
         description
           "Contains various services provided by the gateway.";
@@ -63,10 +64,18 @@
           if-feature uverse;
         }
       }
+      list flow {
+        description
+          "Each flow represents a subscriber flow into the VSG instance.";
+        leaf id {
+          type yang:uuid;
+        }
+      }
     }
     list port {
       description
-        "Each entry represents a VSG endpoint connected across VSG gateways.";
+        "Each entry represents a VSG subscriber flow connected across VSG
+         gateways.";
       key id;
       leaf id {
         description "OpenFlow Port ID";
@@ -75,7 +84,7 @@
       }
       leaf link {
         type leafref {
-          path '../../gateway/id';
+          path '../../gateway/flow/id';
         }
         mandatory true;
       }
diff --git a/schema/xos-core.yang b/schema/xos-core.yang
index 1137c28..b7d2462 100644
--- a/schema/xos-core.yang
+++ b/schema/xos-core.yang
@@ -136,7 +136,6 @@
       uses sync-record;
     }
   }
-
   grouping tenant-root {
     uses base-common {
       refine 'name' {
@@ -152,21 +151,21 @@
       // not exactly clear how this is populated
     }
   }
-  
   grouping subscriber {
     uses tenant-root {
       refine kind { default subscriber; }
     }
     // seems we should have interesting attributes specific to subscriber?
   }
-  
   grouping provider {
     uses tenant-root {
       refine kind { default provider; }
     }
     // seems we should have interesting attributes specific to provider?
   }
-
+  grouping slice {
+    // TBD
+  }
   grouping service {
     uses base-common {
       refine 'name' {
@@ -220,6 +219,9 @@
       notification subscriber-added;
       notification subscriber-deleted;
     }
+    list slice {
+      uses xos:slice;
+    }
     
     // TOOD: need to better understand relationship between Service and Slice
     action scale {