diff --git a/xos/tosca/custom_types/xos.yaml b/xos/tosca/custom_types/xos.yaml
index b1f6873..fbc8010 100644
--- a/xos/tosca/custom_types/xos.yaml
+++ b/xos/tosca/custom_types/xos.yaml
@@ -3,17 +3,22 @@
 node_types:
     tosca.nodes.Service:
         derived_from: tosca.nodes.Root
+        capabilities:
+            scalable:
+                type tosca.capabilities.Scalable
+#        properties:
+#            persistent:
+#                type: boolean
+#                required: false
+#                default: false
+#                description: prevent this resource from being deleted
 
     tosca.nodes.Site:
         derived_from: tosca.nodes.Root
 
     tosca.nodes.Slice:
         derived_from: tosca.nodes.Root
-        properties:
-#            site:
-#                type: string
-#                required: true
-        
+
     tosca.relationships.MemberOfSlice:
         derived_from: tosca.relationships.Root
 
diff --git a/xos/tosca/engine.py b/xos/tosca/engine.py
index b5ce94b..0801c9b 100644
--- a/xos/tosca/engine.py
+++ b/xos/tosca/engine.py
@@ -105,7 +105,7 @@
 	return order + noorder
 
     def execute(self, user):
-        for nodetemplate in self.ordered_nodetemplates: # self.template.nodetemplates:
+        for nodetemplate in self.ordered_nodetemplates:
             self.execute_nodetemplate(user, nodetemplate)
 
     def execute_nodetemplate(self, user, nodetemplate):
@@ -115,13 +115,6 @@
             obj = cls(user, nodetemplate)
             obj.create_or_update()
 
-    def execute_nodetemplate(self, user, nodetemplate):
-        if nodetemplate.type in resources.resources:
-            cls = resources.resources[nodetemplate.type]
-            print "work on", cls.__name__, nodetemplate.name
-            obj = cls(user, nodetemplate)
-            obj.create_or_update()
-
     def destroy(self, user):
         nodetemplates = self.ordered_nodetemplates
         models = []
@@ -129,9 +122,10 @@
             if nodetemplate.type in resources.resources:
                 cls = resources.resources[nodetemplate.type]
                 obj = cls(user, nodetemplate)
-                models = models + list(obj.get_existing_objs())
+                for model in obj.get_existing_objs():
+                    models.append( (obj, model) )
         models.reverse()
-        for model in models:
+        for (resource,model) in models:
             print "destroying", model
-            model.delete(purge=True) # XXX change before deploying
+            resource.delete(model)
 
diff --git a/xos/tosca/resources/service.py b/xos/tosca/resources/service.py
index fb394e4..12b0464 100644
--- a/xos/tosca/resources/service.py
+++ b/xos/tosca/resources/service.py
@@ -42,3 +42,9 @@
 
         self.info("Created Service '%s'" % (str(service), ))
 
+    def delete(self, obj):
+        if obj.slices.exists():
+            self.info("Service %s has active slices; skipping delete" % obj.name)
+            return
+        obj.delete()
+
diff --git a/xos/tosca/resources/slice.py b/xos/tosca/resources/slice.py
index 7e63ba0..7ac45f7 100644
--- a/xos/tosca/resources/slice.py
+++ b/xos/tosca/resources/slice.py
@@ -30,4 +30,11 @@
 
         self.info("Created Slice '%s' on Site '%s'" % (str(slice), str(slice.site)))
 
+    def delete(self, obj):
+        if obj.slivers.exists():
+            self.info("Slice %s has active slivers; skipping delete" % obj.name)
+            return
+        super(XOSSlice, self).delete(obj)
+
+
 
diff --git a/xos/tosca/resources/xosresource.py b/xos/tosca/resources/xosresource.py
index 573c167..04ee4aa 100644
--- a/xos/tosca/resources/xosresource.py
+++ b/xos/tosca/resources/xosresource.py
@@ -74,6 +74,9 @@
     def update(self, obj):
         pass
 
+    def delete(self, obj):
+        obj.delete(purge=True)   # XXX TODO: turn off purge before production
+
     def info(self, s):
         print s