diff --git a/ipalib/public.py b/ipalib/public.py
index f6bad7ec9..071d905d3 100644
--- a/ipalib/public.py
+++ b/ipalib/public.py
@@ -39,6 +39,10 @@ def is_rule(obj):
 
 
 class option(object):
+	"""
+	The option class represents a kw argument from a command.
+	"""
+
 	__public__ = frozenset((
 		'normalize',
 		'validate',
@@ -64,6 +68,21 @@ class option(object):
 				self.__class__.__name__, value, self.type
 			)
 
+	def validate(self, value):
+		"""
+		Calls each validation rule and if any rule fails, raises RuleError,
+		which is a subclass of ValidationError.
+		"""
+		for rule in self.rules:
+			msg = rule(value)
+			if msg is not None:
+				raise errors.RuleError(
+					self.__class__.__name__,
+					value,
+					rule,
+					msg,
+				)
+
 	def __get_rules(self):
 		"""
 		Returns the tuple of rule methods used for input validation. This
@@ -91,21 +110,12 @@ class option(object):
 				if is_rule(attr):
 					yield attr
 
-	def validate(self, value):
-		for rule in self.rules:
-			msg = rule(value)
-			if msg is not None:
-				raise errors.RuleError(
-					self.__class__.__name__,
-					value,
-					rule,
-					msg,
-				)
-
-
-
-
-
+	def default(self, **kw):
+		"""
+		Returns a default or auto-completed value for this option. If no
+		default is available, this method should return None.
+		"""
+		return None
 
 
 class cmd(plugable.Plugin):
@@ -146,7 +156,6 @@ class cmd(plugable.Plugin):
 		return self.__opt
 	opt = property(__get_opt)
 
-
 	def normalize_iter(self, kw):
 		for (key, value) in kw.items():
 			if key in self.options:
@@ -164,9 +173,12 @@ class cmd(plugable.Plugin):
 			if key in self.options:
 				self.options.validate(value)
 
-
-
-
+	def default(self, **kw):
+		for opt in self.options:
+			if opt.name not in kw:
+				value = opt.default(**kw)
+				if value is not None:
+					kw[opt.name] = value
 
 	def __call__(self, **kw):
 		(args, kw) = self.normalize(*args, **kw)
diff --git a/ipalib/tests/test_public.py b/ipalib/tests/test_public.py
index 3ef7ad087..f05a9c31b 100644
--- a/ipalib/tests/test_public.py
+++ b/ipalib/tests/test_public.py
@@ -93,32 +93,9 @@ class test_option():
 		#assert issubclass(cls, plugable.ReadOnly)
 		assert type(cls.rules) is property
 
-	def test_rules(self):
-		"""
-		Test the rules property.
-		"""
-		o = self.sub()()
-		assert len(o.rules) == 3
-		def get_rule(i):
-			return getattr(o, 'rule_%d' % i)
-		rules = tuple(get_rule(i) for i in xrange(3))
-		assert o.rules == rules
-
-	def test_validation(self):
-		"""
-		Test the validation method.
-		"""
-		o = self.sub()()
-		o.validate(9)
-		for i in xrange(3):
-			e = raises(errors.RuleError, o.validate, i)
-			assert e.error == 'cannot be %d' % i
-
 	def test_normalize(self):
 		sub = self.sub()
-
 		i = sub()
-
 		# Test with values that can't be converted:
 		nope = (
 			'7.0'
@@ -145,6 +122,30 @@ class test_option():
 		for val in okay:
 			assert i.normalize(val) == 7
 
+	def test_rules(self):
+		"""
+		Test the rules property.
+		"""
+		o = self.sub()()
+		assert len(o.rules) == 3
+		def get_rule(i):
+			return getattr(o, 'rule_%d' % i)
+		rules = tuple(get_rule(i) for i in xrange(3))
+		assert o.rules == rules
+
+	def test_validation(self):
+		"""
+		Test the validation method.
+		"""
+		o = self.sub()()
+		o.validate(9)
+		for i in xrange(3):
+			e = raises(errors.RuleError, o.validate, i)
+			assert e.error == 'cannot be %d' % i
+			assert e.value == i
+
+
+
 def test_cmd():
 	cls = public.cmd
 	assert issubclass(cls, plugable.Plugin)