diff --git a/src/knowledge.c b/src/knowledge.c
index e626658..2c2202a 100644
--- a/src/knowledge.c
+++ b/src/knowledge.c
@@ -83,6 +83,7 @@ emptyKnowledge ()
   know->encrypt = NULL;
   know->inverses = NULL;
   know->vars = NULL;
+  know->publicfunctions = NULL;
   return know;
 }
 
@@ -110,6 +111,7 @@ knowledgeDuplicate (Knowledge know)
   newknow->encrypt = termlistShallow (know->encrypt);
   newknow->vars = termlistShallow (know->vars);
   newknow->inverses = know->inverses;
+  newknow->publicfunctions = termlistShallow (know->publicfunctions);
   return newknow;
 }
 
@@ -126,6 +128,7 @@ knowledgeDelete (Knowledge know)
       termlistDelete (know->basic);
       termlistDelete (know->encrypt);
       termlistDelete (know->vars);
+      termlistDelete (know->publicfunctions);
       free (know);
     }
 }
@@ -145,6 +148,7 @@ knowledgeDestroy (Knowledge know)
       termlistDestroy (know->encrypt);
       termlistDestroy (know->vars);
       // termlistDestroy(know->inverses);
+      termlistDestroy (know->publicfunctions);
       free (know);
     }
 }
@@ -483,3 +487,18 @@ knowledgeSubstDo (const Knowledge know)
   /* otherwise a copy (for deletion) is returned. */
   return knowledgeReconstruction (know);
 }
+
+//! Add public function
+void
+knowledgeAddPublicFunction (const Knowledge know, const Term f)
+{
+  know->publicfunctions = termlistAdd (know->publicfunctions, f);
+  return;
+}
+
+//! Check public function
+int
+isKnowledgePublicFunction (const Knowledge know, const Term f)
+{
+  return inTermlist (know->publicfunctions, f);
+}
diff --git a/src/knowledge.h b/src/knowledge.h
index 8893f4d..18d15d1 100644
--- a/src/knowledge.h
+++ b/src/knowledge.h
@@ -42,6 +42,8 @@ struct knowledge
    * and we need to reconstruct the knowledge set.
    */
   Termlist vars;		// special: denotes unsubstituted variables
+  //! A list of public functions
+  Termlist publicfunctions;
 };
 
 //! Shorthand for knowledge pointer.
@@ -67,6 +69,8 @@ Termlist knowledgeSet (const Knowledge know);
 Termlist knowledgeGetInverses (const Knowledge know);
 int knowledgeSubstNeeded (const Knowledge know);
 Knowledge knowledgeSubstDo (const Knowledge know);
+void knowledgeAddPublicFunction (const Knowledge know, const Term f);
+int isKnowledgePublicFunction (const Knowledge know, const Term f);
 
 //! Harnass macro for recursive procedures.
 #define mindwipe(k,recurse) \