diff --git a/knowledge/knowing.py b/knowledge/knowing.py
index 1e21b6e..48248dd 100644
--- a/knowledge/knowing.py
+++ b/knowledge/knowing.py
@@ -44,24 +44,24 @@ class Knowing(object):
         del self._knowledge[obj]
         del obj._knowers[self]
 
-    def getMissingKnowledge(self, position):
-        knowledge = self.getKnowledge()
+    def getMissingKnowledge(self, profile):
+        knowledge = list(self.getKnowledge())
         missing = []
-        toCheck = [k for k in position.getRequirements() if k not in knowledge]
+        toCheck = [k for k in profile.getRequirements() if k not in knowledge]
         while toCheck:
             k = toCheck.pop()
             missing.insert(0, k)
             for d in k.getDependencies():
-                if d in knowledge or k in toCheck:
+                if d in knowledge or d in toCheck:
                     continue
                 if d in missing:
-                    # TODO: rearrange missing, but care for cycles...
+                # TODO: rearrange missing, but care for cycles...
                     continue
                 toCheck.append(d)
         return tuple(missing)
 
-    def getProvidersNeeded(self, position):
+    def getProvidersNeeded(self, profile):
         return ((k, k.getProviders())
-                    for k in self.getMissingKnowledge(position))
+                    for k in self.getMissingKnowledge(profile))
 
 
diff --git a/knowledge/provider.py b/knowledge/provider.py
index 73c608b..e64025d 100644
--- a/knowledge/provider.py
+++ b/knowledge/provider.py
@@ -40,7 +40,7 @@ class KnowledgeProvider(object):
         self._providedKnowledge[obj] = True
         obj._providers.add(self)
 
-    def removeDependency(self, obj):
+    def removeProvidedKnowledge(self, obj):
         del self._providedKnowledge[obj]
         del obj._providers[self]