diff --git a/GPy/core/parameterization/index_operations.py b/GPy/core/parameterization/index_operations.py
index 7fc76d07..78c0d2b9 100644
--- a/GPy/core/parameterization/index_operations.py
+++ b/GPy/core/parameterization/index_operations.py
@@ -22,15 +22,44 @@ def extract_properties_to_index(index, props):
 
 
 class ParameterIndexOperations(object):
-    '''
-    Index operations for storing param index _properties
-    This class enables index with slices retrieved from object.__getitem__ calls.
-    Adding an index will add the selected indexes by the slice of an indexarray
-    indexing a shape shaped array to the flattened index array. Remove will
-    remove the selected slice indices from the flattened array.
-    You can give an offset to set an offset for the given indices in the
-    index array, for multi-param handling.
-    '''
+    """
+    This object wraps a dictionary, whos keys are _operations_ that we'd like
+    to apply to a parameter array, and whose values are np integer arrays which
+    index the parameter array appropriately.
+    
+    A model instance will contain one instance of this class for each thing
+    that needs indexing (i.e. constraints, ties and priors). Parameters within
+    the model constain instances of the ParameterIndexOperationsView class,
+    which can map from a 'local' index (starting 0) to this global index.
+    
+    Here's an illustration:
+    
+    #=======================================================================
+    model : 0 1 2 3 4 5 6 7 8 9
+    key1: 4 5
+    key2: 7 8
+    
+    param1: 0 1 2 3 4 5
+    key1: 2 3
+    key2: 5
+    
+    param2: 0 1 2 3 4
+    key1: 0
+    key2: 2 3
+    #=======================================================================
+    
+    The views of this global index have a subset of the keys in this global
+    (model) index.
+    
+    Adding a new key (e.g. a constraint) to a view will cause the view to pass
+    the new key to the global index, along with the local index and an offset.
+    This global index then stores the key and the appropriate global index
+    (which can be seen by the view).
+    
+    See also:
+    ParameterIndexOperationsView
+    
+    """
     _offset = 0
     def __init__(self, constraints=None):
         self._properties = IntArrayDict()
diff --git a/GPy/core/parameterization/parameter_core.py b/GPy/core/parameterization/parameter_core.py
index dab5c2d0..1f8b347d 100644
--- a/GPy/core/parameterization/parameter_core.py
+++ b/GPy/core/parameterization/parameter_core.py
@@ -495,6 +495,35 @@ class Indexable(Nameable, Observable):
     #===========================================================================
     # Constrain operations -> done
     #===========================================================================
+    
+    def tie(self, name):
+        #remove any constraints
+        old_const = self.constraints.properties()[:]
+        self.unconstrain()
+
+        #set these parameters to be 'fixed' as in, not optimized
+        self._highest_parent_._set_fixed(self, self._raveled_index())
+
+        #see if a tie exists with that name
+        if name in self._highest_parent_.ties:
+            t = self._highest_parent_.ties[name]
+        else:
+            #create a tie object
+            value = np.atleast_1d(self.param_array)[0]*1
+            import ties_and_remappings
+            t = ties_and_remappings.Tie(value=value, name=name)
+
+            #add the new tie object to the global index
+            self._highest_parent_.ties[name] = t
+            self._highest_parent_.add_parameter(t)
+
+            #constrain the tie as we were constrained
+            if len(old_const)==1:
+                t.constrain(old_const[0])
+
+
+        self.constraints.add(t, self._raveled_index())
+        t.add_tied_parameter(self)
 
     def constrain(self, transform, warning=True, trigger_parent=True):
         """
@@ -784,6 +813,7 @@ class Parameterizable(OptimizationHandlable):
         self._param_array_ = None
         self._added_names_ = set()
         self.__visited = False # for traversing in reverse order we need to know if we were here already
+        self.ties = {}
 
     @property
     def param_array(self):