diff --git a/cms/djangoapps/contentstore/views.py b/cms/djangoapps/contentstore/views.py
index 8f10eadc4b..833662b218 100644
--- a/cms/djangoapps/contentstore/views.py
+++ b/cms/djangoapps/contentstore/views.py
@@ -499,7 +499,7 @@ def load_preview_module(request, preview_id, descriptor, instance_state, shared_
     """
     system = preview_module_system(request, preview_id, descriptor)
     try:
-        module = descriptor.xmodule_constructor(system)(instance_state, shared_state)
+        module = descriptor.xmodule(system)
     except:
         module = ErrorDescriptor.from_descriptor(
             descriptor,
diff --git a/common/lib/capa/capa/capa_problem.py b/common/lib/capa/capa/capa_problem.py
index 451891d067..eb39d8a2c6 100644
--- a/common/lib/capa/capa/capa_problem.py
+++ b/common/lib/capa/capa/capa_problem.py
@@ -83,7 +83,7 @@ class LoncapaProblem(object):
     Main class for capa Problems.
     '''
 
-    def __init__(self, problem_text, id, state=None, seed=None, system=None):
+    def __init__(self, problem_text, id, correct_map=None, done=None, seed=None, system=None):
         '''
         Initializes capa Problem.
 
@@ -91,7 +91,8 @@ class LoncapaProblem(object):
 
          - problem_text (string): xml defining the problem
          - id           (string): identifier for this problem; often a filename (no spaces)
-         - state        (dict): student state
+         - correct_map  (dict): data specifying whether the student has completed the problem
+         - done         (bool): Whether the student has answered the problem
          - seed         (int): random number generator seed (int)
          - system       (ModuleSystem): ModuleSystem instance which provides OS,
                                         rendering, and user context
@@ -103,16 +104,11 @@ class LoncapaProblem(object):
         self.problem_id = id
         self.system = system
         self.seed = seed
+        self.done = done
+        self.correct_map = CorrectMap()
 
-        if state:
-            if 'seed' in state:
-                self.seed = state['seed']
-            if 'student_answers' in state:
-                self.student_answers = state['student_answers']
-            if 'correct_map' in state:
-                self.correct_map.set_dict(state['correct_map'])
-            if 'done' in state:
-                self.done = state['done']
+        if correct_map is not None:
+            self.correct_map.set_dict(correct_map)
 
         # TODO: Does this deplete the Linux entropy pool? Is this fast enough?
         if not self.seed:
diff --git a/common/lib/xmodule/xmodule/abtest_module.py b/common/lib/xmodule/xmodule/abtest_module.py
index 3091b6ec02..0f655ded6c 100644
--- a/common/lib/xmodule/xmodule/abtest_module.py
+++ b/common/lib/xmodule/xmodule/abtest_module.py
@@ -7,6 +7,7 @@ from xmodule.x_module import XModule
 from xmodule.raw_module import RawDescriptor
 from xmodule.xml_module import XmlDescriptor
 from xmodule.exceptions import InvalidDefinitionError
+from .model import String, Scope
 
 DEFAULT = "_DEFAULT_GROUP"
 
@@ -68,37 +69,7 @@ class ABTestDescriptor(RawDescriptor, XmlDescriptor):
 
     template_dir_name = "abtest"
 
-    def __init__(self, system, definition=None, **kwargs):
-        """
-        definition is a dictionary with the following layout:
-            {'data': {
-                'experiment': 'the name of the experiment',
-                'group_portions': {
-                    'group_a': 0.1,
-                    'group_b': 0.2
-                },
-                'group_contents': {
-                    'group_a': [
-                        'url://for/content/module/1',
-                        'url://for/content/module/2',
-                    ],
-                    'group_b': [
-                        'url://for/content/module/3',
-                    ],
-                    DEFAULT: [
-                        'url://for/default/content/1'
-                    ]
-                }
-            },
-            'children': [
-                'url://for/content/module/1',
-                'url://for/content/module/2',
-                'url://for/content/module/3',
-                'url://for/default/content/1',
-            ]}
-        """
-        kwargs['shared_state_key'] = definition['data']['experiment']
-        RawDescriptor.__init__(self, system, definition, **kwargs)
+    experiment = String(help="Experiment that this A/B test belongs to", scope=Scope.content)
 
     @classmethod
     def definition_from_xml(cls, xml_object, system):
diff --git a/common/lib/xmodule/xmodule/capa_module.py b/common/lib/xmodule/xmodule/capa_module.py
index 9922b1b8a0..6ad6de2be6 100644
--- a/common/lib/xmodule/xmodule/capa_module.py
+++ b/common/lib/xmodule/xmodule/capa_module.py
@@ -19,6 +19,9 @@ from progress import Progress
 from xmodule.x_module import XModule
 from xmodule.raw_module import RawDescriptor
 from xmodule.exceptions import NotFoundError
+from .model import Int, Scope, ModuleScope, ModelType, String, Boolean, Object, Float
+
+Date = Timedelta = ModelType
 
 log = logging.getLogger("mitx.courseware")
 
@@ -77,6 +80,17 @@ class CapaModule(XModule):
     '''
     icon_class = 'problem'
 
+    attempts = Int(help="Number of attempts taken by the student on this problem", default=0, scope=Scope.student_state)
+    max_attempts = Int(help="Maximum number of attempts that a student is allowed", scope=Scope.settings)
+    due = Date(help="Date that this problem is due by", scope=Scope.settings)
+    graceperiod = Timedelta(help="Amount of time after the due date that submissions will be accepted", scope=Scope.settings)
+    show_answer = String(help="When to show the problem answer to the student", scope=Scope.settings, default="closed")
+    force_save_button = Boolean(help="Whether to force the save button to appear on the page", scope=Scope.settings)
+    rerandomize = String(help="When to rerandomize the problem", default="always")
+    data = String(help="XML data for the problem", scope=Scope.content)
+    correct_map = Object(help="Dictionary with the correctness of current student answers", scope=Scope.student_state)
+    done = Boolean(help="Whether the student has answered the problem", scope=Scope.student_state)
+
     js = {'coffee': [resource_string(__name__, 'js/src/capa/display.coffee'),
                      resource_string(__name__, 'js/src/collapsible.coffee'),
                      resource_string(__name__, 'js/src/javascript_loader.coffee'),
@@ -87,51 +101,15 @@ class CapaModule(XModule):
     js_module_name = "Problem"
     css = {'scss': [resource_string(__name__, 'css/capa/display.scss')]}
 
-    def __init__(self, system, location, definition, descriptor, instance_state=None,
-                 shared_state=None, **kwargs):
-        XModule.__init__(self, system, location, definition, descriptor, instance_state,
-                         shared_state, **kwargs)
+    def __init__(self, system, location, descriptor, model_data):
+        XModule.__init__(self, system, location, descriptor, model_data)
 
-        self.attempts = 0
-        self.max_attempts = None
-
-        dom2 = etree.fromstring(definition['data'])
-
-        display_due_date_string = self.metadata.get('due', None)
-        if display_due_date_string is not None:
-            self.display_due_date = dateutil.parser.parse(display_due_date_string)
-            #log.debug("Parsed " + display_due_date_string +
-            #          " to " + str(self.display_due_date))
-        else:
-            self.display_due_date = None
-
-        grace_period_string = self.metadata.get('graceperiod', None)
-        if grace_period_string is not None and self.display_due_date:
-            self.grace_period = parse_timedelta(grace_period_string)
-            self.close_date = self.display_due_date + self.grace_period
+        if self.graceperiod is not None and self.due:
+            self.close_date = self.due + self.graceperiod
             #log.debug("Then parsed " + grace_period_string +
             #          " to closing date" + str(self.close_date))
         else:
-            self.grace_period = None
-            self.close_date = self.display_due_date
-
-        self.max_attempts = self.metadata.get('attempts', None)
-        if self.max_attempts is not None:
-            self.max_attempts = int(self.max_attempts)
-
-        self.show_answer = self.metadata.get('showanswer', 'closed')
-
-        self.force_save_button = self.metadata.get('force_save_button', 'false')
-
-        if self.show_answer == "":
-            self.show_answer = "closed"
-
-        if instance_state is not None:
-            instance_state = json.loads(instance_state)
-        if instance_state is not None and 'attempts' in instance_state:
-            self.attempts = instance_state['attempts']
-
-        self.name = only_one(dom2.xpath('/problem/@name'))
+            self.close_date = self.due
 
         if self.rerandomize == 'never':
             self.seed = 1
@@ -148,8 +126,8 @@ class CapaModule(XModule):
         try:
             # TODO (vshnayder): move as much as possible of this work and error
             # checking to descriptor load time
-            self.lcp = LoncapaProblem(self.definition['data'], self.location.html_id(),
-                                      instance_state, seed=self.seed, system=self.system)
+            self.lcp = LoncapaProblem(self.data, self.location.html_id(),
+                                      self.correct_map, self.done, self.seed, self.system)
         except Exception as err:
             msg = 'cannot create LoncapaProblem {loc}: {err}'.format(
                 loc=self.location.url(), err=err)
@@ -168,33 +146,21 @@ class CapaModule(XModule):
                                 (self.location.url(), msg))
                 self.lcp = LoncapaProblem(
                     problem_text, self.location.html_id(),
-                    instance_state, seed=self.seed, system=self.system)
+                    self.correct_map, self.done, self.seed, self.system)
             else:
                 # add extra info and raise
                 raise Exception(msg), None, sys.exc_info()[2]
 
-    @property
-    def rerandomize(self):
-        """
-        Property accessor that returns self.metadata['rerandomize'] in a
-        canonical form
-        """
-        rerandomize = self.metadata.get('rerandomize', 'always')
-        if rerandomize in ("", "always", "true"):
-            return "always"
-        elif rerandomize in ("false", "per_student"):
-            return "per_student"
-        elif rerandomize == "never":
-            return "never"
-        elif rerandomize == "onreset":
-            return "onreset"
-        else:
-            raise Exception("Invalid rerandomize attribute " + rerandomize)
+        if self.rerandomize in ("", "true"):
+            self.rerandomize = "always"
+        elif self.rerandomize == "false":
+            self.rerandomize = "per_student"
 
-    def get_instance_state(self):
-        state = self.lcp.get_state()
-        state['attempts'] = self.attempts
-        return json.dumps(state)
+    def sync_lcp_state(self):
+        lcp_state = self.lcp.get_state()
+        self.done = lcp_state['done']
+        self.correct_map = lcp_state['correct_map']
+        self.seed = lcp_state['seed']
 
     def get_score(self):
         return self.lcp.get_score()
@@ -211,7 +177,7 @@ class CapaModule(XModule):
         if total > 0:
             try:
                 return Progress(score, total)
-            except Exception as err:
+            except Exception:
                 log.exception("Got bad progress")
                 return None
         return None
@@ -261,8 +227,8 @@ class CapaModule(XModule):
 
                 #   Next, generate a fresh LoncapaProblem
                 self.lcp = LoncapaProblem(self.definition['data'], self.location.html_id(),
-                               state=None, # Tabula rasa
                                seed=self.seed, system=self.system)
+                self.sync_lcp_state()
 
                 # Prepend a scary warning to the student
                 warning  = '<div class="capa_reset">'\
@@ -280,8 +246,8 @@ class CapaModule(XModule):
                 html = warning
                 try:
                     html += self.lcp.get_html()
-                except Exception, err: # Couldn't do it. Give up
-                    log.exception(err)
+                except Exception:  # Couldn't do it. Give up
+                    log.exception("Unable to generate html from LoncapaProblem")
                     raise
 
         content = {'name': self.display_name,
@@ -311,7 +277,7 @@ class CapaModule(XModule):
 
         # User submitted a problem, and hasn't reset. We don't want
         # more submissions.
-        if self.lcp.done and self.rerandomize == "always":
+        if self.done and self.rerandomize == "always":
             check_button = False
             save_button = False
 
@@ -320,7 +286,7 @@ class CapaModule(XModule):
             reset_button = False
 
         # User hasn't submitted an answer yet -- we don't want resets
-        if not self.lcp.done:
+        if not self.done:
             reset_button = False
 
         # We may not need a "save" button if infinite number of attempts and
@@ -406,7 +372,7 @@ class CapaModule(XModule):
             return self.attempts > 0
 
         if self.show_answer == 'answered':
-            return self.lcp.done
+            return self.done
 
         if self.show_answer == 'closed':
             return self.closed()
@@ -429,6 +395,7 @@ class CapaModule(XModule):
         queuekey = get['queuekey']
         score_msg = get['xqueue_body']
         self.lcp.update_score(score_msg, queuekey)
+        self.sync_lcp_state()
 
         return dict()  # No AJAX return is needed
 
@@ -445,8 +412,9 @@ class CapaModule(XModule):
             raise NotFoundError('Answer is not available')
         else:
             answers = self.lcp.get_question_answers()
+            self.sync_lcp_state()
 
-	    # answers (eg <solution>) may have embedded images
+        # answers (eg <solution>) may have embedded images
         #   but be careful, some problems are using non-string answer dicts
         new_answers = dict()
         for answer_id in answers:
@@ -512,7 +480,7 @@ class CapaModule(XModule):
             raise NotFoundError('Problem is closed')
 
         # Problem submitted. Student should reset before checking again
-        if self.lcp.done and self.rerandomize == "always":
+        if self.done and self.rerandomize == "always":
             event_info['failure'] = 'unreset'
             self.system.track_function('save_problem_check_fail', event_info)
             raise NotFoundError('Problem must be reset before it can be checked again')
@@ -522,14 +490,13 @@ class CapaModule(XModule):
             current_time = datetime.datetime.now()
             prev_submit_time = self.lcp.get_recentmost_queuetime()
             waittime_between_requests = self.system.xqueue['waittime']
-            if (current_time-prev_submit_time).total_seconds() < waittime_between_requests:
+            if (current_time - prev_submit_time).total_seconds() < waittime_between_requests:
                 msg = 'You must wait at least %d seconds between submissions' % waittime_between_requests
-                return {'success': msg, 'html': ''} # Prompts a modal dialog in ajax callback
+                return {'success': msg, 'html': ''}  # Prompts a modal dialog in ajax callback
 
         try:
-            old_state = self.lcp.get_state()
-            lcp_id = self.lcp.problem_id
             correct_map = self.lcp.grade_answers(answers)
+            self.sync_lcp_state()
         except StudentInputError as inst:
             log.exception("StudentInputError in capa_module:problem_check")
             return {'success': inst.message}
@@ -554,11 +521,11 @@ class CapaModule(XModule):
         #       'success' will always be incorrect
         event_info['correct_map'] = correct_map.get_dict()
         event_info['success'] = success
-	event_info['attempts'] = self.attempts
+        event_info['attempts'] = self.attempts
         self.system.track_function('save_problem_check', event_info)
 
-	if hasattr(self.system,'psychometrics_handler'):	# update PsychometricsData using callback
-		self.system.psychometrics_handler(self.get_instance_state())
+        if hasattr(self.system, 'psychometrics_handler'):  # update PsychometricsData using callback
+            self.system.psychometrics_handler(self.get_instance_state())
 
         # render problem into HTML
         html = self.get_problem_html(encapsulate=False)
@@ -589,7 +556,7 @@ class CapaModule(XModule):
 
         # Problem submitted. Student should reset before saving
         # again.
-        if self.lcp.done and self.rerandomize == "always":
+        if self.done and self.rerandomize == "always":
             event_info['failure'] = 'done'
             self.system.track_function('save_problem_fail', event_info)
             return {'success': False,
@@ -617,7 +584,7 @@ class CapaModule(XModule):
             return {'success': False,
                     'error': "Problem is closed"}
 
-        if not self.lcp.done:
+        if not self.done:
             event_info['failure'] = 'not_done'
             self.system.track_function('reset_problem_fail', event_info)
             return {'success': False,
@@ -629,9 +596,13 @@ class CapaModule(XModule):
             # in next line)
             self.lcp.seed = None
 
-        self.lcp = LoncapaProblem(self.definition['data'],
-                                  self.location.html_id(), self.lcp.get_state(),
-                                  system=self.system)
+        self.lcp = LoncapaProblem(self.data,
+                                  self.location.html_id(),
+                                  self.lcp.correct_map,
+                                  self.lcp.done,
+                                  self.lcp.seed,
+                                  self.system)
+        self.sync_lcp_state()
 
         event_info['new_state'] = self.lcp.get_state()
         self.system.track_function('reset_problem', event_info)
@@ -647,6 +618,8 @@ class CapaDescriptor(RawDescriptor):
 
     module_class = CapaModule
 
+    weight = Float(help="How much to weight this problem by", scope=Scope.settings)
+
     stores_state = True
     has_score = True
     template_dir_name = 'problem'
@@ -665,12 +638,3 @@ class CapaDescriptor(RawDescriptor):
             'problems/' + path[8:],
             path[8:],
         ]
-
-    def __init__(self, *args, **kwargs):
-        super(CapaDescriptor, self).__init__(*args, **kwargs)
-
-        weight_string = self.metadata.get('weight', None)
-        if weight_string:
-            self.weight = float(weight_string)
-        else:
-            self.weight = None
diff --git a/common/lib/xmodule/xmodule/course_module.py b/common/lib/xmodule/xmodule/course_module.py
index 474cec0a45..019a79e7ab 100644
--- a/common/lib/xmodule/xmodule/course_module.py
+++ b/common/lib/xmodule/xmodule/course_module.py
@@ -12,6 +12,9 @@ import requests
 import time
 import copy
 
+from .model import Scope, ModelType, List, String, Object, Boolean
+
+Date = ModelType
 
 log = logging.getLogger(__name__)
 
@@ -21,6 +24,39 @@ edx_xml_parser = etree.XMLParser(dtd_validation=False, load_dtd=False,
 class CourseDescriptor(SequenceDescriptor):
     module_class = SequenceModule
 
+    textbooks = List(help="List of pairs of (title, url) for textbooks used in this course", default=[], scope=Scope.content)
+    wiki_slug = String(help="Slug that points to the wiki for this course", scope=Scope.content)
+    enrollment_start = Date(help="Date that enrollment for this class is opened", scope=Scope.settings)
+    enrollment_end = Date(help="Date that enrollment for this class is closed", scope=Scope.settings)
+    end = Date(help="Date that this class ends", scope=Scope.settings)
+    advertised_start = Date(help="Date that this course is advertised to start", scope=Scope.settings)
+    grading_policy = Object(help="Grading policy definition for this class", scope=Scope.content)
+
+    info_sidebar_name = String(scope=Scope.settings, default='Course Handouts')
+    
+    # An extra property is used rather than the wiki_slug/number because
+    # there are courses that change the number for different runs. This allows
+    # courses to share the same css_class across runs even if they have
+    # different numbers.
+    #
+    # TODO get rid of this as soon as possible or potentially build in a robust
+    # way to add in course-specific styling. There needs to be a discussion
+    # about the right way to do this, but arjun will address this ASAP. Also
+    # note that the courseware template needs to change when this is removed.
+    css_class = String(help="DO NOT USE THIS", scope=Scope.settings)
+
+    # TODO: This is a quick kludge to allow CS50 (and other courses) to
+    # specify their own discussion forums as external links by specifying a
+    # "discussion_link" in their policy JSON file. This should later get
+    # folded in with Syllabus, Course Info, and additional Custom tabs in a
+    # more sensible framework later.
+    discussion_link = String(help="DO NOT USE THIS", scope=Scope.settings)
+
+    # TODO: same as above, intended to let internal CS50 hide the progress tab
+    # until we get grade integration set up.
+    # Explicit comparison to True because we always want to return a bool.
+    hide_progress_tab = Boolean(help="DO NOT USE THIS", scope=Scope.settings)
+
     template_dir_name = 'course'
 
     class Textbook:
@@ -69,10 +105,11 @@ class CourseDescriptor(SequenceDescriptor):
 
             return table_of_contents
 
-    def __init__(self, system, definition=None, **kwargs):
-        super(CourseDescriptor, self).__init__(system, definition, **kwargs)
+    def __init__(self, *args, **kwargs):
+        super(CourseDescriptor, self).__init__(*args, **kwargs)
+
         self.textbooks = []
-        for title, book_url in self.definition['data']['textbooks']:
+        for title, book_url in self.textbooks:
             try:
                 self.textbooks.append(self.Textbook(title, book_url))
             except:
@@ -81,7 +118,8 @@ class CourseDescriptor(SequenceDescriptor):
                 log.exception("Couldn't load textbook ({0}, {1})".format(title, book_url))
                 continue
 
-        self.wiki_slug = self.definition['data']['wiki_slug'] or self.location.course
+        if self.wiki_slug is None:
+            self.wiki_slug = self.location.course
 
         msg = None
         if self.start is None:
@@ -98,7 +136,7 @@ class CourseDescriptor(SequenceDescriptor):
         #   disable the syllabus content for courses that do not provide a syllabus
         self.syllabus_present = self.system.resources_fs.exists(path('syllabus'))
 
-        self.set_grading_policy(self.definition['data'].get('grading_policy', None))
+        self.set_grading_policy(self.grading_policy)
 
     def defaut_grading_policy(self):
         """
@@ -203,7 +241,7 @@ class CourseDescriptor(SequenceDescriptor):
         
         # cdodge: import the grading policy information that is on disk and put into the
         # descriptor 'definition' bucket as a dictionary so that it is persisted in the DB
-        instance.definition['data']['grading_policy'] = policy
+        instance.grading_policy = policy
 
         # now set the current instance. set_grading_policy() will apply some inheritance rules
         instance.set_grading_policy(policy)
@@ -395,38 +433,14 @@ class CourseDescriptor(SequenceDescriptor):
 
     @property
     def start_date_text(self):
-        displayed_start = self._try_parse_time('advertised_start') or self.start
-        return time.strftime("%b %d, %Y", displayed_start)
+        return time.strftime("%b %d, %Y", self.advertised_start or self.start)
 
     @property
     def end_date_text(self):
         return time.strftime("%b %d, %Y", self.end)
 
-    # An extra property is used rather than the wiki_slug/number because
-    # there are courses that change the number for different runs. This allows
-    # courses to share the same css_class across runs even if they have
-    # different numbers.
-    #
-    # TODO get rid of this as soon as possible or potentially build in a robust
-    # way to add in course-specific styling. There needs to be a discussion
-    # about the right way to do this, but arjun will address this ASAP. Also
-    # note that the courseware template needs to change when this is removed.
-    @property
-    def css_class(self):
-        return self.metadata.get('css_class', '')
 
-    @property
-    def info_sidebar_name(self):
-        return self.metadata.get('info_sidebar_name', 'Course Handouts')
 
-    @property
-    def discussion_link(self):
-        """TODO: This is a quick kludge to allow CS50 (and other courses) to
-        specify their own discussion forums as external links by specifying a
-        "discussion_link" in their policy JSON file. This should later get
-        folded in with Syllabus, Course Info, and additional Custom tabs in a
-        more sensible framework later."""
-        return self.metadata.get('discussion_link', None)
 
     @property
     def forum_posts_allowed(self):
@@ -443,12 +457,6 @@ class CourseDescriptor(SequenceDescriptor):
         
         return True
 
-    @property
-    def hide_progress_tab(self):
-        """TODO: same as above, intended to let internal CS50 hide the progress tab
-        until we get grade integration set up."""
-        # Explicit comparison to True because we always want to return a bool.
-        return self.metadata.get('hide_progress_tab') == True
 
     @property
     def end_of_course_survey_url(self):
diff --git a/common/lib/xmodule/xmodule/error_module.py b/common/lib/xmodule/xmodule/error_module.py
index 65fceb77c7..0f95bcd256 100644
--- a/common/lib/xmodule/xmodule/error_module.py
+++ b/common/lib/xmodule/xmodule/error_module.py
@@ -74,12 +74,11 @@ class ErrorDescriptor(JSONEditingDescriptor):
         }
 
         # real metadata stays in the content, but add a display name
-        metadata = {'display_name': 'Error: ' + location.name}
+        model_data = {'display_name': 'Error: ' + location.name}
         return ErrorDescriptor(
             system,
-            definition,
-            location=location,
-            metadata=metadata
+            location,
+            model_data,
         )
 
     def get_context(self):
diff --git a/common/lib/xmodule/xmodule/mako_module.py b/common/lib/xmodule/xmodule/mako_module.py
index f5f2fae23b..bdf3cb4749 100644
--- a/common/lib/xmodule/xmodule/mako_module.py
+++ b/common/lib/xmodule/xmodule/mako_module.py
@@ -21,20 +21,19 @@ class MakoModuleDescriptor(XModuleDescriptor):
     the descriptor as the `module` parameter to that template
     """
 
-    def __init__(self, system, definition=None, **kwargs):
+    def __init__(self, system, location, model_data):
         if getattr(system, 'render_template', None) is None:
             raise TypeError('{system} must have a render_template function'
                             ' in order to use a MakoDescriptor'.format(
                     system=system))
-        super(MakoModuleDescriptor, self).__init__(system, definition, **kwargs)
+        super(MakoModuleDescriptor, self).__init__(system, location, model_data)
 
     def get_context(self):
         """
         Return the context to render the mako template with
         """
         return {'module': self,
-                'metadata': self.metadata,
-                'editable_metadata_fields' : self.editable_metadata_fields
+                'editable_metadata_fields': self.editable_fields
                 }
 
     def get_html(self):
@@ -44,6 +43,6 @@ class MakoModuleDescriptor(XModuleDescriptor):
     # cdodge: encapsulate a means to expose "editable" metadata fields (i.e. not internal system metadata)
     @property
     def editable_metadata_fields(self):
-        subset = [name for name in self.metadata.keys() if name not in self.system_metadata_fields]
+        subset = [field.name for field in self.fields if field.name not in self.system_metadata_fields]
         return subset
 
diff --git a/common/lib/xmodule/xmodule/model.py b/common/lib/xmodule/xmodule/model.py
new file mode 100644
index 0000000000..b58ffa267a
--- /dev/null
+++ b/common/lib/xmodule/xmodule/model.py
@@ -0,0 +1,79 @@
+from collections import namedtuple
+
+class ModuleScope(object):
+    USAGE, DEFINITION, TYPE, ALL = xrange(4)
+
+
+class Scope(namedtuple('ScopeBase', 'student module')):
+    pass
+
+Scope.content = Scope(student=False, module=ModuleScope.DEFINITION)
+Scope.student_state = Scope(student=True, module=ModuleScope.USAGE)
+Scope.settings = Scope(student=True, module=ModuleScope.USAGE)
+Scope.student_preferences = Scope(student=True, module=ModuleScope.TYPE)
+Scope.student_info = Scope(student=True, module=ModuleScope.ALL)
+
+
+class ModelType(object):
+    sequence = 0
+
+    def __init__(self, help=None, default=None, scope=Scope.content):
+        self._seq = self.sequence
+        self._name = "unknown"
+        self.help = help
+        self.default = default
+        self.scope = scope
+        ModelType.sequence += 1
+
+    @property
+    def name(self):
+        return self._name
+
+    def __get__(self, instance, owner):
+        if instance is None:
+            return self
+
+        return instance._model_data.get(self.name, self.default)
+
+    def __set__(self, instance, value):
+        instance._model_data[self.name] = value
+
+    def __delete__(self, instance):
+        del instance._model_data[self.name]
+
+    def __repr__(self):
+        return "<{0.__class__.__name} {0.__name__}>".format(self)
+
+    def __lt__(self, other):
+        return self._seq < other._seq
+
+Int = Float = Boolean = Object = List = String = Any = ModelType
+
+
+class ModelMetaclass(type):
+    def __new__(cls, name, bases, attrs):
+        # Find registered methods
+        reg_methods = {}
+        for value in attrs.itervalues():
+            for reg_type, names in getattr(value, "_method_registrations", {}).iteritems():
+                for n in names:
+                    reg_methods[reg_type + n] = value
+        attrs['registered_methods'] = reg_methods
+
+        if attrs.get('has_children', False):
+            attrs['children'] = ModelType(help='The children of this XModule', default=[], scope=None)
+
+            @property
+            def child_map(self):
+                return dict((child.name, child) for child in self.children)
+            attrs['child_map'] = child_map
+
+        fields = []
+        for n, v in attrs.items():
+            if isinstance(v, ModelType):
+                v._name = n
+                fields.append(v)
+        fields.sort()
+        attrs['fields'] = fields
+
+        return super(ModelMetaclass, cls).__new__(cls, name, bases, attrs)
diff --git a/common/lib/xmodule/xmodule/modulestore/xml.py b/common/lib/xmodule/xmodule/modulestore/xml.py
index e3ad1fb0dd..7c6887696e 100644
--- a/common/lib/xmodule/xmodule/modulestore/xml.py
+++ b/common/lib/xmodule/xmodule/modulestore/xml.py
@@ -187,12 +187,13 @@ class ImportSystem(XMLParsingSystem, MakoDescriptorSystem):
                     err_msg
                 )
 
-            descriptor.metadata['data_dir'] = course_dir
+            setattr(descriptor, 'data_dir', course_dir)
 
             xmlstore.modules[course_id][descriptor.location] = descriptor
 
-            for child in descriptor.get_children():
-                parent_tracker.add_parent(child.location, descriptor.location)
+            if hasattr(descriptor, 'children'):
+                for child in descriptor.children:
+                    parent_tracker.add_parent(child.location, descriptor.location)
             return descriptor
 
         render_template = lambda: ''
@@ -425,14 +426,14 @@ class XMLModuleStore(ModuleStoreBase):
             # breaks metadata inheritance via get_children().  Instead
             # (actually, in addition to, for now), we do a final inheritance pass
             # after we have the course descriptor.
-            XModuleDescriptor.compute_inherited_metadata(course_descriptor)
+            #XModuleDescriptor.compute_inherited_metadata(course_descriptor)
 
             # now import all pieces of course_info which is expected to be stored
             # in <content_dir>/info or <content_dir>/info/<url_name>
             self.load_extra_content(system, course_descriptor, 'course_info', self.data_dir / course_dir / 'info', course_dir, url_name)
 
             # now import all static tabs which are expected to be stored in
-            # in <content_dir>/tabs or <content_dir>/tabs/<url_name>           
+            # in <content_dir>/tabs or <content_dir>/tabs/<url_name>
             self.load_extra_content(system, course_descriptor, 'static_tab', self.data_dir / course_dir / 'tabs', course_dir, url_name)
 
             self.load_extra_content(system, course_descriptor, 'custom_tag_template', self.data_dir / course_dir / 'custom_tags', course_dir, url_name)
@@ -444,30 +445,30 @@ class XMLModuleStore(ModuleStoreBase):
 
     def load_extra_content(self, system, course_descriptor, category, base_dir, course_dir, url_name):
         if url_name:
-            path =  base_dir / url_name
+            path = base_dir / url_name
 
         if not os.path.exists(path):
             path = base_dir
 
-        for filepath in glob.glob(path/ '*'):
+        for filepath in glob.glob(path / '*'):
             with open(filepath) as f:
                 try:
                     html = f.read().decode('utf-8')
                     # tabs are referenced in policy.json through a 'slug' which is just the filename without the .html suffix
                     slug = os.path.splitext(os.path.basename(filepath))[0]
                     loc = Location('i4x', course_descriptor.location.org, course_descriptor.location.course, category, slug)
-                    module = HtmlDescriptor(system, definition={'data' : html}, **{'location' : loc})
+                    module = HtmlDescriptor(system, loc, {'data': html})
                     # VS[compat]:
                     # Hack because we need to pull in the 'display_name' for static tabs (because we need to edit them)
                     # from the course policy
                     if category == "static_tab":
                         for tab in course_descriptor.tabs or []:
                             if tab.get('url_slug') == slug:
-                                module.metadata['display_name'] = tab['name']            
-                    module.metadata['data_dir'] = course_dir
-                    self.modules[course_descriptor.id][module.location] = module   
+                                module.display_name = tab['name']
+                    module.data_dir = course_dir
+                    self.modules[course_descriptor.id][module.location] = module
                 except Exception, e:
-                    logging.exception("Failed to load {0}. Skipping... Exception: {1}".format(filepath, str(e)))   
+                    logging.exception("Failed to load {0}. Skipping... Exception: {1}".format(filepath, str(e)))
                     system.error_tracker("ERROR: " + str(e))
 
     def get_instance(self, course_id, location, depth=0):
diff --git a/common/lib/xmodule/xmodule/template_module.py b/common/lib/xmodule/xmodule/template_module.py
index 07ef2c6511..f14254c011 100644
--- a/common/lib/xmodule/xmodule/template_module.py
+++ b/common/lib/xmodule/xmodule/template_module.py
@@ -67,10 +67,6 @@ class CustomTagDescriptor(RawDescriptor):
         return template.render(**params)
 
 
-    def __init__(self, system, definition, **kwargs):
-        '''Render and save the template for this descriptor instance'''
-        super(CustomTagDescriptor, self).__init__(system, definition, **kwargs)
-
     @property
     def rendered_html(self):
         return self.render_template(self.system, self.definition['data'])
diff --git a/common/lib/xmodule/xmodule/x_module.py b/common/lib/xmodule/xmodule/x_module.py
index 690f78fd53..9cf45652ca 100644
--- a/common/lib/xmodule/xmodule/x_module.py
+++ b/common/lib/xmodule/xmodule/x_module.py
@@ -2,19 +2,41 @@ import logging
 import pkg_resources
 import yaml
 import os
+import time
 
-from functools import partial
 from lxml import etree
 from pprint import pprint
 from collections import namedtuple
 from pkg_resources import resource_listdir, resource_string, resource_isdir
 
 from xmodule.modulestore import Location
-from xmodule.timeparse import parse_time, stringify_time
+from .model import ModelMetaclass, String, Scope, ModuleScope, ModelType
 
-from xmodule.contentstore.content import StaticContent, XASSET_SRCREF_PREFIX
-from xmodule.modulestore.exceptions import ItemNotFoundError
-import time
+Date = ModelType
+
+
+class Date(ModelType):
+    time_format = "%Y-%m-%dT%H:%M"
+
+    def from_json(self, value):
+        """
+        Parse an optional metadata key containing a time: if present, complain
+        if it doesn't parse.
+        Return None if not present or invalid.
+        """
+        try:
+            return time.strptime(value, self.time_format)
+        except ValueError as e:
+            msg = "Field {0} has bad value '{1}': '{2}'".format(
+                self._name, value, e)
+            log.warning(msg)
+            return None
+
+    def to_json(self, value):
+        """
+        Convert a time struct to a string
+        """
+        return time.strftime(self.time_format, value)
 
 log = logging.getLogger('mitx.' + __name__)
 
@@ -157,6 +179,10 @@ class XModule(HTMLSnippet):
         See the HTML module for a simple example.
     '''
 
+    __metaclass__ = ModelMetaclass
+
+    display_name = String(help="Display name for this module", scope=Scope(student=False, module=ModuleScope.USAGE))
+
     # The default implementation of get_icon_class returns the icon_class
     # attribute of the class
     #
@@ -165,8 +191,7 @@ class XModule(HTMLSnippet):
     # in the module
     icon_class = 'other'
 
-    def __init__(self, system, location, definition, descriptor,
-                 instance_state=None, shared_state=None, **kwargs):
+    def __init__(self, system, location, descriptor, model_data):
         '''
         Construct a new xmodule
 
@@ -214,63 +239,25 @@ class XModule(HTMLSnippet):
         '''
         self.system = system
         self.location = Location(location)
-        self.definition = definition
         self.descriptor = descriptor
-        self.instance_state = instance_state
-        self.shared_state = shared_state
         self.id = self.location.url()
         self.url_name = self.location.name
         self.category = self.location.category
-        self.metadata = kwargs.get('metadata', {})
-        self._loaded_children = None
+        self._model_data = model_data
 
-    @property
-    def display_name(self):
-        '''
-        Return a display name for the module: use display_name if defined in
-        metadata, otherwise convert the url name.
-        '''
-        return self.metadata.get('display_name',
-                                 self.url_name.replace('_', ' '))
+        if self.display_name is None:
+            self.display_name = self.url_name.replace('_', ' ')
 
     def __unicode__(self):
         return '<x_module(id={0})>'.format(self.id)
 
-    def get_children(self):
-        '''
-        Return module instances for all the children of this module.
-        '''
-        if self._loaded_children is None:
-            child_locations = self.get_children_locations()
-            children = [self.system.get_module(loc) for loc in child_locations]
-            # get_module returns None if the current user doesn't have access
-            # to the location.
-            self._loaded_children = [c for c in children if c is not None]
-
-        return self._loaded_children
-    
-    def get_children_locations(self):
-        '''
-        Returns the locations of each of child modules.
-        
-        Overriding this changes the behavior of get_children and
-        anything that uses get_children, such as get_display_items.
-        
-        This method will not instantiate the modules of the children
-        unless absolutely necessary, so it is cheaper to call than get_children
-        
-        These children will be the same children returned by the
-        descriptor unless descriptor.has_dynamic_children() is true.
-        '''
-        return self.definition.get('children', [])
-
     def get_display_items(self):
         '''
         Returns a list of descendent module instances that will display
         immediately inside this module.
         '''
         items = []
-        for child in self.get_children():
+        for child in self.children():
             items.extend(child.displayable_items())
 
         return items
@@ -290,18 +277,6 @@ class XModule(HTMLSnippet):
 
     ### Functions used in the LMS
 
-    def get_instance_state(self):
-        ''' State of the object, as stored in the database
-        '''
-        return '{}'
-
-    def get_shared_state(self):
-        '''
-        Get state that should be shared with other instances
-        using the same 'shared_state_key' attribute.
-        '''
-        return '{}'
-
     def get_score(self):
         ''' Score the student received on the problem.
         '''
@@ -391,7 +366,10 @@ class XModuleDescriptor(Plugin, HTMLSnippet, ResourceTemplates):
     """
     entry_point = "xmodule.v1"
     module_class = XModule
+    __metaclass__ = ModelMetaclass
 
+    display_name = String(help="Display name for this module", scope=Scope(student=False, module=ModuleScope.USAGE))
+    start = Date(help="Start time when this module is visible", scope=Scope(student=False, module=ModuleScope.USAGE))
     # Attributes for inspection of the descriptor
     stores_state = False  # Indicates whether the xmodule state should be
     # stored in a database (independent of shared state)
@@ -424,8 +402,8 @@ class XModuleDescriptor(Plugin, HTMLSnippet, ResourceTemplates):
     # ============================= STRUCTURAL MANIPULATION ===================
     def __init__(self,
                  system,
-                 definition=None,
-                 **kwargs):
+                 location,
+                 model_data):
         """
         Construct a new XModuleDescriptor. The only required arguments are the
         system, used for interaction with external resources, and the
@@ -467,116 +445,36 @@ class XModuleDescriptor(Plugin, HTMLSnippet, ResourceTemplates):
                     instance of the module data
         """
         self.system = system
-        self.metadata = kwargs.get('metadata', {})
-        self.definition = definition if definition is not None else {}
-        self.location = Location(kwargs.get('location'))
+        self.location = Location(location)
         self.url_name = self.location.name
         self.category = self.location.category
-        self.shared_state_key = kwargs.get('shared_state_key')
+        self._model_data = model_data
 
         self._child_instances = None
         self._inherited_metadata = set()
 
-    @property
-    def display_name(self):
-        '''
-        Return a display name for the module: use display_name if defined in
-        metadata, otherwise convert the url name.
-        '''
-        return self.metadata.get('display_name',
-                                 self.url_name.replace('_', ' '))
-
-    @property
-    def start(self):
-        """
-        If self.metadata contains start, return it.  Else return None.
-        """
-        if 'start' not in self.metadata:
-            return None
-        return self._try_parse_time('start')
-
-    @start.setter
-    def start(self, value):
-        if isinstance(value, time.struct_time):
-            self.metadata['start'] = stringify_time(value)
-        
-    @property
-    def own_metadata(self):
-        """
-        Return the metadata that is not inherited, but was defined on this module.
-        """
-        return dict((k, v) for k, v in self.metadata.items()
-                    if k not in self._inherited_metadata)
-
-    @staticmethod
-    def compute_inherited_metadata(node):
-        """Given a descriptor, traverse all of its descendants and do metadata
-        inheritance.  Should be called on a CourseDescriptor after importing a
-        course.
-
-        NOTE: This means that there is no such thing as lazy loading at the
-        moment--this accesses all the children."""
-        for c in node.get_children():
-            c.inherit_metadata(node.metadata)
-            XModuleDescriptor.compute_inherited_metadata(c)
-
-    def inherit_metadata(self, metadata):
-        """
-        Updates this module with metadata inherited from a containing module.
-        Only metadata specified in self.inheritable_metadata will
-        be inherited
-        """
-        # Set all inheritable metadata from kwargs that are
-        # in self.inheritable_metadata and aren't already set in metadata
-        for attr in self.inheritable_metadata:
-            if attr not in self.metadata and attr in metadata:
-                self._inherited_metadata.add(attr)
-                self.metadata[attr] = metadata[attr]
-
-    def get_children(self):
-        """Returns a list of XModuleDescriptor instances for the children of
-        this module"""
-        if self._child_instances is None:
-            self._child_instances = []
-            for child_loc in self.definition.get('children', []):
-                try:
-                    child = self.system.load_item(child_loc)
-                except ItemNotFoundError:
-                    log.exception('Unable to load item {loc}, skipping'.format(loc=child_loc))
-                    continue
-                # TODO (vshnayder): this should go away once we have
-                # proper inheritance support in mongo.  The xml
-                # datastore does all inheritance on course load.
-                child.inherit_metadata(self.metadata)
-                self._child_instances.append(child)
-
-        return self._child_instances
-
     def get_child_by_url_name(self, url_name):
         """
         Return a child XModuleDescriptor with the specified url_name, if it exists, and None otherwise.
         """
-        for c in self.get_children():
+        for c in self.children:
             if c.url_name == url_name:
                 return c
         return None
 
-    def xmodule_constructor(self, system):
+    def xmodule(self, system):
         """
         Returns a constructor for an XModule. This constructor takes two
         arguments: instance_state and shared_state, and returns a fully
         instantiated XModule
         """
-        return partial(
-            self.module_class,
+        return self.module_class(
             system,
             self.location,
-            self.definition,
             self,
-            metadata=self.metadata
+            system.xmodule_model_data(self.model_data),
         )
     
-    
     def has_dynamic_children(self):
         """
         Returns True if this descriptor has dynamic children for a given
@@ -701,31 +599,14 @@ class XModuleDescriptor(Plugin, HTMLSnippet, ResourceTemplates):
         return eq
 
     def __repr__(self):
-        return ("{class_}({system!r}, {definition!r}, location={location!r},"
-                " metadata={metadata!r})".format(
+        return ("{class_}({system!r}, location={location!r},"
+                " model_data={model_data!r})".format(
             class_=self.__class__.__name__,
             system=self.system,
-            definition=self.definition,
             location=self.location,
-            metadata=self.metadata
+            model_data=self._model_data,
         ))
 
-    # ================================ Internal helpers =======================
-
-    def _try_parse_time(self, key):
-        """
-        Parse an optional metadata key containing a time: if present, complain
-        if it doesn't parse.
-        Return None if not present or invalid.
-        """
-        if key in self.metadata:
-            try:
-                return parse_time(self.metadata[key])
-            except ValueError as e:
-                msg = "Descriptor {0} loaded with a bad metadata key '{1}': '{2}'".format(
-                    self.location.url(), self.metadata[key], e)
-                log.warning(msg)
-        return None
 
 
 class DescriptorSystem(object):
@@ -867,6 +748,9 @@ class ModuleSystem(object):
         '''provide uniform access to attributes (like etree)'''
         self.__dict__[attr] = val
 
+    def xmodule_module_data(self, module_data):
+        return module_data
+
     def __repr__(self):
         return repr(self.__dict__)
 
diff --git a/common/lib/xmodule/xmodule/xml_module.py b/common/lib/xmodule/xmodule/xml_module.py
index 38fcaddd20..36bea6edb2 100644
--- a/common/lib/xmodule/xmodule/xml_module.py
+++ b/common/lib/xmodule/xmodule/xml_module.py
@@ -287,9 +287,9 @@ class XmlDescriptor(XModuleDescriptor):
             filepath = cls._format_filepath(xml_object.tag, name_to_pathname(url_name))
             definition_xml = cls.load_file(filepath, system.resources_fs, location)
         else:
-            definition_xml = xml_object	# this is just a pointer, not the real definition content
+            definition_xml = xml_object  # this is just a pointer, not the real definition content
 
-        definition = cls.load_definition(definition_xml, system, location)	# note this removes metadata
+        definition = cls.load_definition(definition_xml, system, location)  # note this removes metadata
         # VS[compat] -- make Ike's github preview links work in both old and
         # new file layouts
         if is_pointer_tag(xml_object):
@@ -299,13 +299,13 @@ class XmlDescriptor(XModuleDescriptor):
         metadata = cls.load_metadata(definition_xml)
 
         # move definition metadata into dict
-        dmdata = definition.get('definition_metadata','')
+        dmdata = definition.get('definition_metadata', '')
         if dmdata:
             metadata['definition_metadata_raw'] = dmdata
             try:
                 metadata.update(json.loads(dmdata))
             except Exception as err:
-                log.debug('Error %s in loading metadata %s' % (err,dmdata))
+                log.debug('Error %s in loading metadata %s' % (err, dmdata))
                 metadata['definition_metadata_err'] = str(err)
 
         # Set/override any metadata specified by policy
@@ -313,11 +313,14 @@ class XmlDescriptor(XModuleDescriptor):
         if k in system.policy:
             cls.apply_policy(metadata, system.policy[k])
 
+        model_data = {}
+        model_data.update(metadata)
+        model_data.update(definition)
+
         return cls(
             system,
-            definition,
-            location=location,
-            metadata=metadata,
+            location,
+            model_data,
         )
 
     @classmethod
diff --git a/jenkins/base.sh b/jenkins/base.sh
new file mode 100644
index 0000000000..c7175e6e52
--- /dev/null
+++ b/jenkins/base.sh
@@ -0,0 +1,12 @@
+
+function github_status {
+    gcli status create mitx mitx $GIT_COMMIT \
+         --params=$1 \
+                  target_url:$BUILD_URL \
+                  description:"Build #$BUILD_NUMBER is running" \
+         -f csv
+}
+
+function github_mark_failed_on_exit {
+    trap '[ $? == "0" ] || github_status state:failed' EXIT
+}
\ No newline at end of file
diff --git a/lms/djangoapps/courseware/courses.py b/lms/djangoapps/courseware/courses.py
index 643382b485..5312a228a4 100644
--- a/lms/djangoapps/courseware/courses.py
+++ b/lms/djangoapps/courseware/courses.py
@@ -85,7 +85,7 @@ def course_image_url(course):
     """Try to look up the image url for the course.  If it's not found,
     log an error and return the dead link"""
     if isinstance(modulestore(), XMLModuleStore):
-        path = course.metadata['data_dir'] + "/images/course_image.jpg"
+        path = course.data_dir + "/images/course_image.jpg"
         return try_staticfiles_lookup(path)
     else:
         loc = course.location._replace(tag='c4x', category='asset', name='images_course_image.jpg')
@@ -162,7 +162,9 @@ def get_course_about_section(course, section_key):
                 key=section_key, url=course.location.url()))
             return None
     elif section_key == "title":
-        return course.metadata.get('display_name', course.url_name)
+        if course.display_name is None:
+            return course.url_name
+        return course.display_name
     elif section_key == "university":
         return course.location.org
     elif section_key == "number":
@@ -220,7 +222,7 @@ def get_course_syllabus_section(course, section_key):
             filepath = find_file(fs, dirs, section_key + ".html")
             with fs.open(filepath) as htmlFile:
                 return replace_urls(htmlFile.read().decode('utf-8'),
-                                    course.metadata['data_dir'], course_namespace=course.location)
+                                    course.data_dir, course_namespace=course.location)
         except ResourceNotFoundError:
             log.exception("Missing syllabus section {key} in course {url}".format(
                 key=section_key, url=course.location.url()))
diff --git a/lms/djangoapps/courseware/module_render.py b/lms/djangoapps/courseware/module_render.py
index 9343301fb7..9c40767e99 100644
--- a/lms/djangoapps/courseware/module_render.py
+++ b/lms/djangoapps/courseware/module_render.py
@@ -245,7 +245,7 @@ def _get_module(user, request, location, student_module_cache, course_id, positi
                    make_psychometrics_data_update_handler(instance_module))
 
     try:
-        module = descriptor.xmodule_constructor(system)(instance_state, shared_state)
+        module = descriptor.xmodule(system)
     except:
         log.exception("Error creating module from descriptor {0}".format(descriptor))
 
@@ -259,7 +259,7 @@ def _get_module(user, request, location, student_module_cache, course_id, positi
                                                               error_msg=exc_info_to_str(sys.exc_info()))
 
         # Make an error module
-        return err_descriptor.xmodule_constructor(system)(None, None)
+        return err_descriptor.xmodule(system)
 
     _get_html = module.get_html
 
diff --git a/rakefile b/rakefile
index ca20de9a39..adf16cc462 100644
--- a/rakefile
+++ b/rakefile
@@ -40,7 +40,7 @@ end
 
 def django_admin(system, env, command, *args)
     django_admin = ENV['DJANGO_ADMIN_PATH'] || select_executable('django-admin.py', 'django-admin')
-    return "#{django_admin} #{command} --settings=#{system}.envs.#{env} --pythonpath=. #{args.join(' ')}"
+    return "#{django_admin} #{command} --traceback --settings=#{system}.envs.#{env} --pythonpath=. #{args.join(' ')}"
 end
 
 def django_for_jasmine(system, django_reload)