--- a/configuration/config.py	Sat Mar 24 22:25:24 2012 -0700
+++ b/configuration/config.py	Sat Mar 24 23:14:22 2012 -0700
@@ -20,6 +20,8 @@
 except ImportError:
     yaml = None
 
+__all__ = ['Configuration', 'configuration_providers']
+
 configuration_providers = []
 if json:
     class JSON(object):
@@ -30,25 +32,37 @@
     class YAML(object):
         extensions = ['yml']
         def read(self, filename):
-            pass
+            f = file(filename)
+            config = yaml.load(f)
+            f.close()
+            return config
+
     configuration_providers.append(YAML)
 
-__all__ = ['Configuration']
 
 class Configuration(object):
     options = {}
 
-    def __init__(self):
+    def __init__(self, configuration_providers=configuration_providers):
         self.config = {}
+        self.configuration_providers = configuration_providers
 
-    def check(self):
+    def check(self, config):
         """check validity of configuration"""
 
+        # TODO: ensure options in configuration are in self.options
+        unknown_options = []
+
+        #
+
     def __call__(self, *args):
         """add items to configuration and check it"""
 
     def add(self, config):
         """update configuration: not undoable"""
+
+        self.check(config)
+
         self.config.update(config)
         # TODO: option to extend; augment lists/dicts