diff --git a/driver.py b/driver.py
index d9805e1..df92aa2 100755
--- a/driver.py
+++ b/driver.py
@@ -57,7 +57,7 @@ def load_relations():
 
             print ("Loading relation %s with name %s..." % (i, relname))
 
-            rels[relname] = relation.Relation('%s%s' % (examples_path, i))
+            rels[relname] = relation.Relation.load('%s%s' % (examples_path, i))
             print('done')
 
 
@@ -163,7 +163,8 @@ def run_py_test(testname):
     '''Runs a python test, which evaluates expressions directly rather than queries'''
     print ("Running expression python test: " +
            colorize(testname, COLOR_MAGENTA))
-
+    exp_result = None
+    result = None
     try:
 
         expr = readfile('%s%s.python' % (tests_path, testname))
@@ -238,7 +239,7 @@ def run_test(testname):
     o_result = None
 
     try:
-        result_rel = relation.Relation('%s%s.result' % (tests_path, testname))
+        result_rel = relation.Relation.load('%s%s.result' % (tests_path, testname))
 
         query = readfile('%s%s.query' % (tests_path, testname)).strip()
         o_query = optimizer.optimize_all(query, rels)
diff --git a/relational/maintenance.py b/relational/maintenance.py
index 01a2374..5afa527 100644
--- a/relational/maintenance.py
+++ b/relational/maintenance.py
@@ -91,7 +91,7 @@ class UserInterface:
     def load(self, filename: str, name: str) -> None:
         '''Loads a relation from file, and gives it a name to
         be used in subsequent queries.'''
-        rel = Relation(filename)
+        rel = Relation.load(filename)
         self.set_relation(name, rel)
 
     def unload(self, name: str) -> None:
@@ -204,7 +204,7 @@ class UserInterface:
         [varname =] query
         to assign the result to a new relation
         '''
-        r = Relation()
+        r = None
         queries = query.split('\n')
         for query in queries:
             if query.strip() == '':
@@ -219,4 +219,6 @@ class UserInterface:
                     query,
                     str(e)
                 ))
+        if r is None:
+            raise Exception('No query executed')
         return r