--- a/configuration/configuration.py	Wed Mar 28 08:38:16 2012 -0700
+++ b/configuration/configuration.py	Wed Mar 28 09:03:02 2012 -0700
@@ -9,7 +9,7 @@
 import sys
 import optparse
 
-# imports for contigent configuration providers
+# imports for configuration providers
 try:
     import json
 except ImportError:
@@ -22,10 +22,20 @@
 except ImportError:
     yaml = None
 
-__all__ = ['Configuration', 'configuration_providers', 'types', 'MissingValueException', 'ConfigurationProviderException', 'TypeCastException', 'ConfigurationOption']
+__all__ = ['Configuration',
+           'configuration_providers',
+           'types',
+           'UnknownOptionException',
+           'MissingValueException',
+           'ConfigurationProviderException',
+           'TypeCastException',
+           'ConfigurationOption']
 
 ### exceptions
 
+class UnknownOptionException(Exception):
+    """exception raised when a non-configuration value is present in the configuration"""
+
 class MissingValueException(Exception):
     """exception raised when a required value is missing"""
 
@@ -35,6 +45,7 @@
 class TypeCastException(Exception):
     """exception raised when a configuration item cannot be coerced to a type"""
 
+
 ### configuration providers for serialization/deserialization
 
 configuration_providers = []
@@ -219,7 +230,7 @@
 
 
     ### methods for iteration
-    ### TODO: make this a real iterator
+    ### TODO: make the class a real iterator
 
     def items(self):
         # TODO: allow options to be a list of 2-tuples
@@ -231,18 +242,18 @@
         """
         check validity of configuration to be added
         """
-        # TODO: should probably deepcopy config
 
         # ensure options in configuration are in self.options
         unknown_options = [i for i in config if i not in self.options]
         if unknown_options:
-            # TODO: more specific error type
-            raise Exception("Unknown options: %s" % ', '.join(unknown_options))
+            raise UnknownOptionException("Unknown options: %s" % ', '.join(unknown_options))
 
-        # TODO: ensure options are of the right type (if specified)
+        # ensure options are of the right type (if specified)
         for key, value in config.items():
             _type = self.options[key].get('type')
-            if _type is not None:
+            if _type is None and 'default' in self.options[key]:
+                _type = type(self.options[key]['default'])
+            if _type is not None and not isinstance(value, _type):
                 try:
                     config[key] = _type(value)
                 except BaseException, e:
@@ -252,6 +263,7 @@
 
     def validate(self):
         """validate resultant configuration"""
+
         for key, value in self.options.items():
             if key not in self.config:
                 required = value.get('required')
@@ -260,8 +272,7 @@
                         required_message = required
                     else:
                         required_message = "Parameter %s is required but not present" % key
-                    # TODO: more specific exception
-                    # Also, this should probably raise all missing values vs
+                    # TODO: this should probably raise all missing values vs
                     # one by one
                     raise MissingValueException(required_message)
         # TODO: configuration should be locked after this is called
@@ -270,6 +281,7 @@
 
     def __call__(self, *args):
         """add items to configuration and check it"""
+
         for config in args:
             self.add(config)