diff --git a/AlgebraicDataflowArchitectureModel/models/InventoryManagement.model b/AlgebraicDataflowArchitectureModel/models/InventoryManagement.model
index c41ed3c..31bcdad 100644
--- a/AlgebraicDataflowArchitectureModel/models/InventoryManagement.model
+++ b/AlgebraicDataflowArchitectureModel/models/InventoryManagement.model
@@ -1,7 +1,10 @@
 channel ItemRegistration {
-	out inventory(items:Map, registerItem(itemId:Str, quantity:Int)) = insert(items, itemId, {"count": quantity})
+	out inventory(itemDB:Map, registerItem(itemId:Str, itemName:Str, quantity:Int)) = insert(itemDB, itemId, {"count": quantity, 
+																											"name": itemName})
 }
 
 channel ReceivingOrShipping(itemId:Str) {
-	out inventory.{itemId}.count(prev_quantity:Int, receiveOrship(quantity:Int)) = prev_quantity + quantity
+	out inventory.{itemId}.count(prev_quantity:Int, receiveOrShip(quantity:Int)) = if(prev_quantity + quantity >= 0, 
+																						prev_quantity + quantity, 
+																						prev_quantity)
 }
diff --git a/AlgebraicDataflowArchitectureModel/models/SimpleTwitter.model b/AlgebraicDataflowArchitectureModel/models/SimpleTwitter.model
index cea527d..5e0d048 100644
--- a/AlgebraicDataflowArchitectureModel/models/SimpleTwitter.model
+++ b/AlgebraicDataflowArchitectureModel/models/SimpleTwitter.model
@@ -1,7 +1,8 @@
 channel Signup{
-	out accounts(accountMap:Map, signUp(accountId:Str, name:Str)) = insert(accountMap, accountId, {"name": name, "tweets": nil})
+	out accounts(accountDB:Map, signUp(accountId:Str, name:Str)) = insert(accountDB, accountId, {"name": name, 
+																									"tweets": nil})
 }
 
 channel Tweet(accountId:Str) {
-	out accounts.{accountId}.tweets(tweetList:List, tweet(contents:Str)) = append(tweetList, contents)
+	out accounts.{accountId}.tweets(tweetDB:Map, tweet(tweetId:Str, contents:Str)) = insert(tweetDB, tweetId, contents)
 }