diff --git a/lib/models/change.js b/lib/models/change.js
index 7a09373d..410bab7a 100644
--- a/lib/models/change.js
+++ b/lib/models/change.js
@@ -179,7 +179,7 @@ Change.prototype.rectify = function(cb) {
   function updateCheckpoint(cb) {
     change.constructor.getCheckpointModel().current(function(err, checkpoint) {
       if(err) return Change.handleError(err);
-      change.checkpoint = ++checkpoint;
+      change.checkpoint = checkpoint;
       cb();
     });
   }
@@ -328,7 +328,7 @@ Change.diff = function(modelName, since, remoteChanges, callback) {
     where: {
       modelName: modelName,
       modelId: {inq: modelIds},
-      checkpoint: {gt: since}
+      checkpoint: {gte: since}
     }
   }, function(err, localChanges) {
     if(err) return callback(err);
@@ -400,6 +400,15 @@ Change.handleError = function(err) {
   }
 }
 
+Change.prototype.getModelId = function() {
+  // TODO(ritch) get rid of the need to create an instance
+  var Model = this.constructor.settings.model;
+  var id = this.modelId;
+  var m = new Model();
+  m.setId(id);
+  return m.getId();
+}
+
 /**
  * When two changes conflict a conflict is created.
  *
diff --git a/lib/models/checkpoint.js b/lib/models/checkpoint.js
index 71d4797e..c1fa7d70 100644
--- a/lib/models/checkpoint.js
+++ b/lib/models/checkpoint.js
@@ -11,8 +11,8 @@ var DataModel = require('../loopback').DataModel
  */
 
 var properties = {
-  id: {type: Number, generated: true, id: true},
-  time: {type: Number, generated: true, default: Date.now},
+  seq: {type: Number},
+  time: {type: Date, default: Date},
   sourceId: {type: String}
 };
 
@@ -45,13 +45,33 @@ var Checkpoint = module.exports = DataModel.extend('Checkpoint', properties, opt
  */
 
 Checkpoint.current = function(cb) {
+  var Checkpoint = this;
   this.find({
     limit: 1,
-    sort: 'id DESC'
+    sort: 'seq DESC'
   }, function(err, checkpoints) {
     if(err) return cb(err);
-    var checkpoint = checkpoints[0] || {id: 0};
-    cb(null, checkpoint.id);
+    var checkpoint = checkpoints[0];
+    if(checkpoint) {
+      cb(null, checkpoint.seq);
+    } else {
+      Checkpoint.create({seq: 0}, function(err, checkpoint) {
+        if(err) return cb(err);
+        cb(null, checkpoint.seq);
+      });
+    }
   });
 }
 
+Checkpoint.beforeSave = function(next, model) {
+  if(!model.getId() && model.seq === undefined) {
+    model.constructor.current(function(err, seq) {
+      if(err) return next(err);
+      model.seq = seq + 1;
+      next();
+    });
+  } else {
+    next();
+  }
+}
+
diff --git a/lib/models/data-model.js b/lib/models/data-model.js
index 5aae7536..ade8d8bf 100644
--- a/lib/models/data-model.js
+++ b/lib/models/data-model.js
@@ -3,6 +3,7 @@
  */
 
 var Model = require('./model');
+var loopback = require('../loopback');
 var RemoteObjects = require('strong-remoting');
 var assert = require('assert');
 var async = require('async');
@@ -505,7 +506,7 @@ DataModel.setupRemoting = function() {
         {arg: 'remoteChanges', type: 'array', description: 'an array of change objects',
          http: {source: 'body'}}
       ],      
-      returns: {arg: 'deltas', type: 'array', root: true},
+      returns: {arg: 'result', type: 'object', root: true},
       http: {verb: 'post', path: '/diff'}
     });
 
@@ -532,11 +533,29 @@ DataModel.setupRemoting = function() {
       http: {verb: 'get', path: '/checkpoint'}
     });
 
+    setRemoting(DataModel.createUpdates, {
+      description: 'Create an update list from a delta list',
+      accepts: {arg: 'deltas', type: 'array', http: {source: 'body'}},
+      returns: {arg: 'updates', type: 'array', root: true},
+      http: {verb: 'post', path: '/create-updates'}
+    });
+
     setRemoting(DataModel.bulkUpdate, {
       description: 'Run multiple updates at once. Note: this is not atomic.',
       accepts: {arg: 'updates', type: 'array'},
       http: {verb: 'post', path: '/bulk-update'}
     });
+
+    setRemoting(DataModel.rectifyAllChanges, {
+      description: 'Rectify all Model changes.',
+      http: {verb: 'post', path: '/rectify-all'}
+    });
+
+    setRemoting(DataModel.rectifyChange, {
+      description: 'Tell loopback that a change to the model with the given id has occurred.',
+      accepts: {arg: 'id', type: 'any', http: {source: 'path'}},
+      http: {verb: 'post', path: '/:id/rectify-change'}
+    });
   }
 }
 
@@ -568,6 +587,12 @@ DataModel.diff = function(since, remoteChanges, callback) {
  */
 
 DataModel.changes = function(since, filter, callback) { 
+  if(typeof since === 'function') {
+    filter = {};
+    callback = since;
+    since = -1;
+  }
+
   var idName = this.dataSource.idName(this.modelName);
   var Change = this.getChangeModel();
   var model = this;
@@ -577,14 +602,14 @@ DataModel.changes = function(since, filter, callback) {
   filter.where = filter.where || {};
   filter.fields[idName] = true;
 
-  // this whole thing could be optimized a bit more
+  // TODO(ritch) this whole thing could be optimized a bit more
   Change.find({
     checkpoint: {gt: since},
     modelName: this.modelName
   }, function(err, changes) {
     if(err) return cb(err);
     var ids = changes.map(function(change) {
-      return change.modelId.toString();
+      return change.getModelId();
     });
     filter.where[idName] = {inq: ids};
     model.find(filter, function(err, models) {
@@ -709,7 +734,7 @@ DataModel.replicate = function(since, targetModel, options, callback) {
     if(diff && diff.deltas && diff.deltas.length) {
       sourceModel.createUpdates(diff.deltas, cb);
     } else {
-      // done
+      // nothing to replicate
       callback(null, []);
     }
   }
@@ -863,44 +888,72 @@ DataModel.enableChangeTracking = function() {
   Change.getCheckpointModel().attachTo(this.dataSource);
 
   Model.on('changed', function(obj) {
-    Change.rectifyModelChanges(Model.modelName, [obj.id], function(err) {
-      if(err) {
-        console.error(Model.modelName + ' Change Tracking Error:');
-        console.error(err);
-      }
-    });
+    Model.rectifyChange(obj.getId(), Model.handleChangeError);
   });
 
-  Model.on('deleted', function(obj) {
-    Change.rectifyModelChanges(Model.modelName, [obj.id], function(err) {
-      if(err) {
-        console.error(Model.modelName + ' Change Tracking Error:');
-        console.error(err);
-      }
-    });
+  Model.on('deleted', function(id) {
+    Model.rectifyChange(id, Model.handleChangeError);
   });
 
   Model.on('deletedAll', cleanup);
 
-  // initial cleanup
-  cleanup();
+  if(loopback.isServer) {
+    // initial cleanup
+    cleanup();
 
-  // cleanup
-  setInterval(cleanup, cleanupInterval);
+    // cleanup
+    setInterval(cleanup, cleanupInterval);
 
-  function cleanup() {
-    Change.rectifyAll(function(err) {
-      if(err) {
-        console.error(Model.modelName + ' Change Cleanup Error:');
-        console.error(err);
-      }
-    });
+    function cleanup() {
+      Model.rectifyAllChanges(function(err) {
+        if(err) {
+          console.error(Model.modelName + ' Change Cleanup Error:');
+          console.error(err);
+        }
+      });
+    }
   }
 }
 
 DataModel._defineChangeModel = function() {
   var BaseChangeModel = require('./change');
-  return this.Change = BaseChangeModel.extend(this.modelName + '-change');
+  return this.Change = BaseChangeModel.extend(this.modelName + '-change',
+    {},
+    {
+      model: this
+    }
+  );
+}
+
+DataModel.rectifyAllChanges = function(callback) {
+  this.getChangeModel().rectifyAll(callback);
+}
+
+/**
+ * Handle a change error. Override this method in a subclassing model to customize
+ * change error handling.
+ *
+ * @param {Error} err
+ */
+
+DataModel.handleChangeError = function(err) {
+  if(err) {
+    console.error(Model.modelName + ' Change Tracking Error:');
+    console.error(err);
+  }
+}
+
+/**
+ * Tell loopback that a change to the model with the given id has occurred.
+ *
+ * @param {*} id The id of the model that has changed
+ * @callback {Function} callback
+ * @param {Error} err
+ */
+
+DataModel.rectifyChange = function(id, callback) {
+  var Change = this.getChangeModel();
+  Change.rectifyModelChanges(this.modelName, [id], callback);
 }
 
 DataModel.setup();