diff --git a/src/blenderbim/blenderbim/bim/export_ifc.py b/src/blenderbim/blenderbim/bim/export_ifc.py
index 5290b1215f..c0b52e7ce6 100644
--- a/src/blenderbim/blenderbim/bim/export_ifc.py
+++ b/src/blenderbim/blenderbim/bim/export_ifc.py
@@ -46,9 +46,6 @@ class IfcExporter:
                 jsonData = ifcjson.IFC2JSON5a(self.file, self.ifc_export_settings.json_compact).spf2Json()
                 with open(self.ifc_export_settings.output_file, "w") as outfile:
                     json.dump(jsonData, outfile, indent=None if self.ifc_export_settings.json_compact else 4)
-        if bpy.context.scene.BIMProjectProperties.is_authoring:
-            if bpy.data.filepath:
-                bpy.ops.wm.save_mainfile()
 
     def set_header(self):
         # TODO: add all metadata, pending bug #747
diff --git a/src/blenderbim/blenderbim/bim/handler.py b/src/blenderbim/blenderbim/bim/handler.py
index 7d7d5b6bfc..2626d5335d 100644
--- a/src/blenderbim/blenderbim/bim/handler.py
+++ b/src/blenderbim/blenderbim/bim/handler.py
@@ -9,17 +9,18 @@ from ifcopenshell.api.attribute.data import Data as AttributeData
 
 
 def mode_callback(obj, data):
-    if (
-        obj.mode != "OBJECT"
-        or not obj.data
-        or not isinstance(obj.data, bpy.types.Mesh)
-        or not obj.data.BIMMeshProperties.ifc_definition_id
-        or not bpy.context.scene.BIMProjectProperties.is_authoring
-    ):
-        return
-    representation = IfcStore.get_file().by_id(obj.data.BIMMeshProperties.ifc_definition_id)
-    if representation.RepresentationType == "Tessellation" or representation.RepresentationType == "Brep":
-        IfcStore.edited_objs.add(obj.name)
+    for obj in bpy.context.selected_objects:
+        if (
+            obj.mode != "OBJECT"
+            or not obj.data
+            or not isinstance(obj.data, bpy.types.Mesh)
+            or not obj.data.BIMMeshProperties.ifc_definition_id
+            or not bpy.context.scene.BIMProjectProperties.is_authoring
+        ):
+            return
+        representation = IfcStore.get_file().by_id(obj.data.BIMMeshProperties.ifc_definition_id)
+        if representation.RepresentationType == "Tessellation" or representation.RepresentationType == "Brep":
+            IfcStore.edited_objs.add(obj.name)
 
 
 def name_callback(obj, data):
@@ -81,9 +82,7 @@ def loadIfcStore(scene):
 @persistent
 def ensureIfcExported(scene):
     if IfcStore.get_file() and not bpy.context.scene.BIMProperties.ifc_file:
-        # The invocation pops up a file select window.
-        # This is non-blocking, therefore the Blend file is saved before we export.
-        bpy.ops.export_ifc.bim("INVOKE_DEFAULT", should_force_resave=True)
+        bpy.ops.export_ifc.bim("INVOKE_DEFAULT")
 
 
 @persistent
diff --git a/src/blenderbim/blenderbim/bim/import_ifc.py b/src/blenderbim/blenderbim/bim/import_ifc.py
index eb7a298c4f..f98f0f5082 100644
--- a/src/blenderbim/blenderbim/bim/import_ifc.py
+++ b/src/blenderbim/blenderbim/bim/import_ifc.py
@@ -780,9 +780,6 @@ class IfcImporter:
         if element is None:
             return
 
-        if not self.ifc_import_settings.should_import_spaces and element.is_a("IfcSpace"):
-            return
-
         self.ifc_import_settings.logger.info("Creating object %s", element)
 
         if mesh:
@@ -1084,8 +1081,6 @@ class IfcImporter:
 
     def add_related_objects(self, parent, related_objects):
         for element in related_objects:
-            if element.is_a("IfcSpace"):
-                continue
             global_id = element.GlobalId
             collection = bpy.data.collections.new(self.get_name(element))
             self.spatial_structure_elements[global_id] = {"blender": collection}
@@ -1129,8 +1124,6 @@ class IfcImporter:
             container = element.ContainedInStructure[0].RelatingStructure
         elif hasattr(element, "Decomposes") and element.Decomposes:
             container = element.Decomposes[0].RelatingObject
-        if container.is_a("IfcSpace"):
-            return self.get_aggregate_container(container)
         return container
 
     def create_openings_collection(self):
@@ -1179,9 +1172,7 @@ class IfcImporter:
             and element.ContainedInStructure[0].RelatingStructure
         ):
             container = element.ContainedInStructure[0].RelatingStructure
-            if container.is_a("IfcSpace"):
-                return self.place_object_in_spatial_tree(container, obj)
-            elif element.is_a("IfcGrid"):
+            if element.is_a("IfcGrid"):
                 grid_collection = bpy.data.collections.get(obj.name)
                 if grid_collection:  # Just in case we ran into invalid grids from Revit
                     self.spatial_structure_elements[container.GlobalId]["blender"].children.link(grid_collection)
@@ -1193,22 +1184,15 @@ class IfcImporter:
             if element.Decomposes[0].RelatingObject.is_a("IfcProject"):
                 collection = self.project["blender"]
             elif element.Decomposes[0].RelatingObject.is_a("IfcSpatialStructureElement"):
-                if element.is_a("IfcSpatialStructureElement") and not element.is_a("IfcSpace"):
+                if element.is_a("IfcSpatialStructureElement"):
                     global_id = element.GlobalId
-                else:
-                    global_id = element.Decomposes[0].RelatingObject.GlobalId
                 if global_id in self.spatial_structure_elements:
                     if (
                         element.is_a("IfcSpatialStructureElement")
-                        and not element.is_a("IfcSpace")
                         and "blender_obj" in self.spatial_structure_elements[global_id]
                     ):
                         bpy.data.objects.remove(self.spatial_structure_elements[global_id]["blender_obj"])
                     collection = self.spatial_structure_elements[global_id]["blender"]
-                # This may occur if we are nesting an IfcSpace (which is special
-                # since it does not have a collection within an IfcSpace
-                if not collection:
-                    return self.place_object_in_spatial_tree(element.Decomposes[0].RelatingObject, obj)
             else:
                 collection = self.aggregates[element.Decomposes[0].RelatingObject.GlobalId]["blender"]
             if collection:
@@ -1432,7 +1416,6 @@ class IfcImportSettings:
         self.logger = None
         self.input_file = None
         self.diff_file = None
-        self.should_import_spaces = False
         self.should_auto_set_workarounds = True
         self.should_use_cpu_multiprocessing = True
         self.should_merge_by_class = False
diff --git a/src/blenderbim/blenderbim/bim/module/aggregate/operator.py b/src/blenderbim/blenderbim/bim/module/aggregate/operator.py
index 5d366d5191..27a62fd4d2 100644
--- a/src/blenderbim/blenderbim/bim/module/aggregate/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/aggregate/operator.py
@@ -39,7 +39,8 @@ class AssignObject(bpy.types.Operator):
                 self.remove_collection(bpy.context.scene.collection, spatial_collection)
                 for collection in bpy.data.collections:
                     if collection == relating_collection:
-                        collection.children.link(spatial_collection)
+                        if not collection.children.get(spatial_collection.name):
+                            collection.children.link(spatial_collection)
                         continue
                     self.remove_collection(collection, spatial_collection)
             else:
diff --git a/src/blenderbim/blenderbim/bim/module/cost/__init__.py b/src/blenderbim/blenderbim/bim/module/cost/__init__.py
index ce2d98dc85..7a8a31b1d3 100644
--- a/src/blenderbim/blenderbim/bim/module/cost/__init__.py
+++ b/src/blenderbim/blenderbim/bim/module/cost/__init__.py
@@ -8,8 +8,10 @@ classes = (
     operator.EnableEditingCostSchedule,
     operator.DisableEditingCostSchedule,
     operator.AddCostItem,
+    operator.AddSummaryCostItem,
     operator.ExpandCostItem,
     operator.ContractCostItem,
+    operator.RemoveCostItem,
     prop.CostItem,
     prop.BIMCostProperties,
     ui.BIM_PT_cost_schedules,
diff --git a/src/blenderbim/blenderbim/bim/module/cost/operator.py b/src/blenderbim/blenderbim/bim/module/cost/operator.py
index afc937ea78..86e0cf03df 100644
--- a/src/blenderbim/blenderbim/bim/module/cost/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/cost/operator.py
@@ -120,24 +120,37 @@ class EditCostSchedule(bpy.types.Operator):
         return {"FINISHED"}
 
 
-class AddCostItem(bpy.types.Operator):
-    bl_idname = "bim.add_cost_item"
+class AddSummaryCostItem(bpy.types.Operator):
+    bl_idname = "bim.add_summary_cost_item"
     bl_label = "Add Cost Item"
     cost_schedule: bpy.props.IntProperty()
 
     def execute(self, context):
         props = context.scene.BIMCostProperties
         self.file = IfcStore.get_file()
-        if len(props.cost_items):
-            data = {"cost_item": self.file.by_id(props.cost_items[props.active_cost_item_index].ifc_definition_id)}
-        else:
-            data = {"cost_schedule": self.file.by_id(self.cost_schedule)}
-        ifcopenshell.api.run("cost.add_cost_item", self.file, **data)
+        ifcopenshell.api.run("cost.add_cost_item", self.file, **{
+        "cost_schedule": self.file.by_id(self.cost_schedule)
+        })
         Data.load(self.file)
         bpy.ops.bim.enable_editing_cost_schedule(cost_schedule = self.cost_schedule)
         return {"FINISHED"}
 
 
+class AddCostItem(bpy.types.Operator):
+    bl_idname = "bim.add_cost_item"
+    bl_label = "Add Cost Item"
+    cost_item: bpy.props.IntProperty()
+
+    def execute(self, context):
+        props = context.scene.BIMCostProperties
+        self.file = IfcStore.get_file()
+        data = {"cost_item": self.file.by_id(self.cost_item)}
+        ifcopenshell.api.run("cost.add_cost_item", self.file, **data)
+        Data.load(self.file)
+        bpy.ops.bim.enable_editing_cost_schedule(cost_schedule = props.active_cost_schedule_id)
+        return {"FINISHED"}
+
+
 class ExpandCostItem(bpy.types.Operator):
     bl_idname = "bim.expand_cost_item"
     bl_label = "Expand Cost Item"
@@ -145,9 +158,11 @@ class ExpandCostItem(bpy.types.Operator):
 
     def execute(self, context):
         props = context.scene.BIMCostProperties
+        self.file = IfcStore.get_file()
         contracted_cost_items = json.loads(props.contracted_cost_items)
         contracted_cost_items.remove(self.cost_item)
         props.contracted_cost_items = json.dumps(contracted_cost_items)
+        Data.load(self.file)
         bpy.ops.bim.enable_editing_cost_schedule(cost_schedule = props.active_cost_schedule_id)
         return {"FINISHED"}
 
@@ -159,8 +174,31 @@ class ContractCostItem(bpy.types.Operator):
 
     def execute(self, context):
         props = context.scene.BIMCostProperties
+        self.file = IfcStore.get_file()
         contracted_cost_items = json.loads(props.contracted_cost_items)
         contracted_cost_items.append(self.cost_item)
         props.contracted_cost_items = json.dumps(contracted_cost_items)
+        Data.load(self.file)
+        bpy.ops.bim.enable_editing_cost_schedule(cost_schedule = props.active_cost_schedule_id)
+        return {"FINISHED"}
+
+
+class RemoveCostItem(bpy.types.Operator):
+    bl_idname = "bim.remove_cost_item"
+    bl_label = "Remove Cost item"
+    cost_item: bpy.props.IntProperty()
+
+    def execute(self, context):
+        props = context.scene.BIMCostProperties
+        self.file = IfcStore.get_file()
+        ifcopenshell.api.run(
+            "cost.remove_cost_item",
+            self.file,
+            cost_item=IfcStore.get_file().by_id(self.cost_item),
+        )
+        Data.load(self.file)
+        # contracted_cost_items = json.loads(props.contracted_cost_items)
+        # contracted_cost_items.remove(props.active_cost_item_index)
+        # props.contracted_cost_items = json.dumps(contracted_cost_items)
         bpy.ops.bim.enable_editing_cost_schedule(cost_schedule = props.active_cost_schedule_id)
         return {"FINISHED"}
diff --git a/src/blenderbim/blenderbim/bim/module/cost/ui.py b/src/blenderbim/blenderbim/bim/module/cost/ui.py
index abfc20074b..7c9edc329e 100644
--- a/src/blenderbim/blenderbim/bim/module/cost/ui.py
+++ b/src/blenderbim/blenderbim/bim/module/cost/ui.py
@@ -51,9 +51,8 @@ class BIM_PT_cost_schedules(Panel):
                 row.prop(attribute, "is_null", icon="RADIOBUT_OFF" if attribute.is_null else "RADIOBUT_ON", text="")
 
         row = self.layout.row(align=True)
-        row.label(text="X Cost Items")
-        row.operator("bim.add_cost_item", text="", icon="ADD").cost_schedule = cost_schedule_id
-
+        row.label(text="X Summary Cost Items")
+        row.operator("bim.add_summary_cost_item", text="", icon="ADD").cost_schedule = cost_schedule_id
         self.layout.template_list(
             "BIM_UL_cost_items",
             "",
@@ -72,10 +71,12 @@ class BIM_UL_cost_items(UIList):
                 row.label(text="", icon="BLANK1")
             if item.has_children:
                 if item.is_expanded:
-                    op = row.operator("bim.contract_cost_item", text="", emboss=False, icon="DISCLOSURE_TRI_DOWN")
+                    row.operator("bim.contract_cost_item", text="", emboss=False, icon="DISCLOSURE_TRI_DOWN").cost_item = item.ifc_definition_id
                 else:
-                    op = row.operator("bim.expand_cost_item", text="", emboss=False, icon="DISCLOSURE_TRI_RIGHT")
-                op.cost_item = item.ifc_definition_id
+                    row.operator("bim.expand_cost_item", text="", emboss=False, icon="DISCLOSURE_TRI_RIGHT").cost_item = item.ifc_definition_id
             else:
                 row.label(text="", icon="DOT")
             row.label(text=item.name)
+            row.operator("bim.add_cost_item", text="", icon="ADD").cost_item = item.ifc_definition_id
+            op = row.operator("bim.remove_cost_item", text="", icon="X")
+            op.cost_item = item.ifc_definition_id
diff --git a/src/blenderbim/blenderbim/bim/module/geometry/operator.py b/src/blenderbim/blenderbim/bim/module/geometry/operator.py
index 19f86fa5d5..0047d012eb 100644
--- a/src/blenderbim/blenderbim/bim/module/geometry/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/geometry/operator.py
@@ -104,18 +104,27 @@ class AddRepresentation(bpy.types.Operator):
                 return {"FINISHED"}
 
             box_context_id = get_context_id("Model", "Box", "MODEL_VIEW")
+            old_box = ifcopenshell.util.element.get_representation(product, "Model", "Box", "MODEL_VIEW")
             if (
                 box_context_id
                 and context_of_items.ContextType == "Model"
                 and context_of_items.ContextIdentifier
                 and context_of_items.ContextIdentifier == "Body"
             ):
+                if old_box:
+                    bpy.ops.bim.remove_representation(representation_id=old_box.id(), obj=obj.name)
                 representation_data["context"] = self.file.by_id(box_context_id)
                 new_box = ifcopenshell.api.run("geometry.add_representation", self.file, **representation_data)
                 ifcopenshell.api.run(
                     "geometry.assign_representation", self.file, **{"product": product, "representation": new_box}
                 )
 
+            [
+                bpy.ops.bim.add_style(material=s.material.name)
+                for s in obj.material_slots
+                if not s.material.BIMMaterialProperties.ifc_style_id
+            ]
+
             ifcopenshell.api.run(
                 "geometry.assign_styles",
                 self.file,
diff --git a/src/blenderbim/blenderbim/bim/module/material/operator.py b/src/blenderbim/blenderbim/bim/module/material/operator.py
index e2e9919551..11745bdf7a 100644
--- a/src/blenderbim/blenderbim/bim/module/material/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/material/operator.py
@@ -318,6 +318,10 @@ class EnableEditingAssignedMaterial(bpy.types.Operator):
             material_set_class = "IfcMaterialLayerSet"
         elif product_data["type"] == "IfcMaterialProfileSet":
             material_set_data = Data.profile_sets[product_data["id"]]
+        elif product_data["type"] == "IfcMaterialProfileSetUsage":
+            profile_set_usage = Data.profile_set_usages[product_data["id"]]
+            material_set_data = Data.profile_sets[profile_set_usage["ForProfileSet"]]
+            material_set_class = "IfcMaterialProfileSet"
         elif product_data["type"] == "IfcMaterialList":
             material_set_data = Data.lists[product_data["id"]]
         else:
@@ -409,7 +413,7 @@ class EnableEditingMaterialSetItem(bpy.types.Operator):
             material_set_item_data = Data.constituents[self.material_set_item]
         elif product_data["type"] == "IfcMaterialLayerSet" or product_data["type"] == "IfcMaterialLayerSetUsage":
             material_set_item_data = Data.layers[self.material_set_item]
-        elif product_data["type"] == "IfcMaterialProfileSet":
+        elif product_data["type"] == "IfcMaterialProfileSet" or product_data["type"] == "IfcMaterialProfileSetUsage":
             material_set_item_data = Data.profiles[self.material_set_item]
         else:
             material_set_item_data = {}
@@ -542,7 +546,7 @@ class EditMaterialSetItem(bpy.types.Operator):
                 },
             )
             Data.load_layers()
-        elif product_data["type"] == "IfcMaterialProfileSet":
+        elif product_data["type"] == "IfcMaterialProfileSet" or product_data["type"] == "IfcMaterialProfileSetUsage":
             profile_attributes = {}
             for attribute in props.material_set_item_profile_attributes:
                 if attribute.data_type == "string":
diff --git a/src/blenderbim/blenderbim/bim/module/material/prop.py b/src/blenderbim/blenderbim/bim/module/material/prop.py
index 6b39d95691..4bd7093d69 100644
--- a/src/blenderbim/blenderbim/bim/module/material/prop.py
+++ b/src/blenderbim/blenderbim/bim/module/material/prop.py
@@ -70,6 +70,7 @@ def getMaterialTypes(self, context):
             "IfcMaterialLayerSet",
             "IfcMaterialLayerSetUsage",
             "IfcMaterialProfileSet",
+            "IfcMaterialProfileSetUsage",
             "IfcMaterialList",
         ]
         if IfcStore.get_file().schema == "IFC2X3":
diff --git a/src/blenderbim/blenderbim/bim/module/material/ui.py b/src/blenderbim/blenderbim/bim/module/material/ui.py
index 591fa8ccb3..262a920ef3 100644
--- a/src/blenderbim/blenderbim/bim/module/material/ui.py
+++ b/src/blenderbim/blenderbim/bim/module/material/ui.py
@@ -82,6 +82,13 @@ class BIM_PT_object_material(Panel):
                 self.set_items = self.material_set_data["MaterialProfiles"] or []
                 self.set_data = Data.profiles
                 self.set_item_name = "profile"
+            elif self.product_data["type"] == "IfcMaterialProfileSetUsage":
+                self.material_set_usage = Data.profile_set_usages[self.product_data["id"]]
+                self.material_set_id = self.material_set_usage["ForProfileSet"]
+                self.material_set_data = Data.profile_sets[self.material_set_id]
+                self.set_items = self.material_set_data["MaterialProfiles"] or []
+                self.set_data = Data.profiles
+                self.set_item_name = "profile"
             elif self.product_data["type"] == "IfcMaterialList":
                 self.material_set_id = self.product_data["id"]
                 self.material_set_data = Data.lists[self.material_set_id]
diff --git a/src/blenderbim/blenderbim/bim/module/pset_template/prop.py b/src/blenderbim/blenderbim/bim/module/pset_template/prop.py
index 36b8bc8c05..83b134c399 100644
--- a/src/blenderbim/blenderbim/bim/module/pset_template/prop.py
+++ b/src/blenderbim/blenderbim/bim/module/pset_template/prop.py
@@ -65,7 +65,7 @@ def getPsetTemplates(self, context):
             IfcStore.pset_template_file = ifcopenshell.open(IfcStore.pset_template_path)
         templates = IfcStore.pset_template_file.by_type("IfcPropertySetTemplate")
         psettemplates_enum.extend([(str(t.id()), t.Name, "") for t in templates])
-        Data.load(IfcStore.get_file())
+        Data.load(IfcStore.pset_template_file)
     return psettemplates_enum
 
 
diff --git a/src/blenderbim/blenderbim/bim/module/pset_template/ui.py b/src/blenderbim/blenderbim/bim/module/pset_template/ui.py
index 49813c0c96..b252e4e496 100644
--- a/src/blenderbim/blenderbim/bim/module/pset_template/ui.py
+++ b/src/blenderbim/blenderbim/bim/module/pset_template/ui.py
@@ -35,10 +35,8 @@ class BIM_PT_pset_template(Panel):
             row.operator("bim.enable_editing_pset_template", text="", icon="GREASEPENCIL")
             row.operator("bim.remove_pset_template", text="", icon="X")
 
-        # row.operator("bim.save_pset_template", text="", icon="EXPORT")
-
         if not Data.is_loaded and props.pset_template_files:
-            Data.load(IfcStore.get_file())
+            Data.load(IfcStore.pset_template_file)
 
         if not Data.pset_templates:
             return
diff --git a/src/blenderbim/blenderbim/bim/module/root/operator.py b/src/blenderbim/blenderbim/bim/module/root/operator.py
index 0af5b8bddb..a785741d60 100644
--- a/src/blenderbim/blenderbim/bim/module/root/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/root/operator.py
@@ -153,6 +153,7 @@ class AssignClass(bpy.types.Operator):
         collection.objects.link(obj)
         if parent_collection:
             parent_collection.children.link(collection)
+            bpy.ops.bim.assign_object(related_object=obj.name, relating_object=parent_collection.name)
         else:
             bpy.context.scene.collection.children.link(collection)
 
diff --git a/src/blenderbim/blenderbim/bim/module/root/ui.py b/src/blenderbim/blenderbim/bim/module/root/ui.py
index d30a7ffe40..6991dbca58 100644
--- a/src/blenderbim/blenderbim/bim/module/root/ui.py
+++ b/src/blenderbim/blenderbim/bim/module/root/ui.py
@@ -39,7 +39,7 @@ class BIM_PT_class(Panel):
                     name += "[{}]".format(data["PredefinedType"])
                 row = self.layout.row(align=True)
                 row.label(text=name)
-                row.operator("bim.copy_class", icon="DUPLICATE", text="").obj = context.active_object.name
+                row.operator("bim.copy_class", icon="DUPLICATE", text="")
                 row.operator("bim.unlink_object", icon="UNLINKED", text="")
                 row.operator("bim.enable_reassign_class", icon="GREASEPENCIL", text="")
                 if context.selected_objects:
diff --git a/src/blenderbim/blenderbim/bim/module/sequence/__init__.py b/src/blenderbim/blenderbim/bim/module/sequence/__init__.py
index 27102da316..9f57dc8d18 100644
--- a/src/blenderbim/blenderbim/bim/module/sequence/__init__.py
+++ b/src/blenderbim/blenderbim/bim/module/sequence/__init__.py
@@ -9,7 +9,6 @@ classes = (
     operator.RemoveWorkPlan,
     operator.EnableEditingWorkPlan,
     operator.DisableEditingWorkPlan,
-    operator.LoadWorkSchedules,
     operator.DisableWorkScheduleEditingUI,
     operator.AddWorkSchedule,
     operator.EditWorkSchedule,
@@ -26,17 +25,19 @@ classes = (
     operator.EnableEditingWorkCalendar,
     operator.DisableEditingWorkCalendar,
     operator.AddTask,
+    operator.AddSummaryTask,
+    operator.ExpandTask,
+    operator.ContractTask,
+    operator.RemoveTask,
     prop.WorkPlan,
     prop.BIMWorkPlanProperties,
     prop.Task,
-    prop.WorkSchedule,
     prop.BIMWorkScheduleProperties,
     prop.WorkCalendar,
     prop.BIMWorkCalendarProperties,
     ui.BIM_PT_work_plans,
     ui.BIM_UL_work_plans,
     ui.BIM_PT_work_schedules,
-    ui.BIM_UL_work_schedules,
     ui.BIM_PT_work_calendars,
     ui.BIM_UL_work_calendars,
     ui.BIM_UL_tasks,
diff --git a/src/blenderbim/blenderbim/bim/module/sequence/operator.py b/src/blenderbim/blenderbim/bim/module/sequence/operator.py
index 1b0ecad74a..b344b7ab3d 100644
--- a/src/blenderbim/blenderbim/bim/module/sequence/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/sequence/operator.py
@@ -123,23 +123,6 @@ class DisableEditingWorkPlan(bpy.types.Operator):
         return {"FINISHED"}
 
 
-class LoadWorkSchedules(bpy.types.Operator):
-    bl_idname = "bim.load_work_schedules"
-    bl_label = "Load Work Schedules"
-
-    def execute(self, context):
-        props = context.scene.BIMWorkScheduleProperties
-        while len(props.work_schedules) > 0:
-            props.work_schedules.remove(0)
-        for ifc_definition_id, work_schedule in Data.work_schedules.items():
-            new = props.work_schedules.add()
-            new.ifc_definition_id = ifc_definition_id
-            new.name = work_schedule["Name"] or "Unnamed"
-        props.is_editing = True
-        bpy.ops.bim.disable_editing_work_schedule()
-        return {"FINISHED"}
-
-
 class DisableWorkScheduleEditingUI(bpy.types.Operator):
     bl_idname = "bim.disable_work_schedule_editing_ui"
     bl_label = "Disable WorkSchedule Editing UI"
@@ -156,7 +139,6 @@ class AddWorkSchedule(bpy.types.Operator):
     def execute(self, context):
         ifcopenshell.api.run("sequence.add_work_schedule", IfcStore.get_file())
         Data.load(IfcStore.get_file())
-        bpy.ops.bim.load_work_schedules()
         return {"FINISHED"}
 
 
@@ -182,7 +164,7 @@ class EditWorkSchedule(bpy.types.Operator):
             **{"work_schedule": self.file.by_id(props.active_work_schedule_id), "attributes": attributes}
         )
         Data.load(IfcStore.get_file())
-        bpy.ops.bim.load_work_schedules()
+        bpy.ops.bim.disable_editing_work_schedule()
         return {"FINISHED"}
 
 
@@ -194,10 +176,11 @@ class RemoveWorkSchedule(bpy.types.Operator):
     def execute(self, context):
         self.file = IfcStore.get_file()
         ifcopenshell.api.run(
-            "sequence.remove_work_schedule", self.file, **{"work_schedule": self.file.by_id(self.work_schedule)}
+            "sequence.remove_work_schedule",
+            self.file,
+            work_schedule= self.file.by_id(self.work_schedule)
         )
         Data.load(self.file)
-        bpy.ops.bim.load_work_schedules()
         return {"FINISHED"}
 
 
@@ -207,9 +190,10 @@ class EnableEditingWorkSchedule(bpy.types.Operator):
     work_schedule: bpy.props.IntProperty()
 
     def execute(self, context):
-        props = context.scene.BIMWorkScheduleProperties
-        while len(props.work_schedule_attributes) > 0:
-            props.work_schedule_attributes.remove(0)
+        self.props = context.scene.BIMWorkScheduleProperties
+        self.props.active_work_schedule_id = self.work_schedule
+        while len(self.props.work_schedule_attributes) > 0:
+            self.props.work_schedule_attributes.remove(0)
 
         data = Data.work_schedules[self.work_schedule]
 
@@ -217,7 +201,7 @@ class EnableEditingWorkSchedule(bpy.types.Operator):
             data_type = ifcopenshell.util.attribute.get_primitive_type(attribute)
             if data_type == "entity":
                 continue
-            new = props.work_schedule_attributes.add()
+            new = self.props.work_schedule_attributes.add()
             new.name = attribute.name()
             new.is_null = data[attribute.name()] is None
             new.is_optional = attribute.optional()
@@ -230,10 +214,30 @@ class EnableEditingWorkSchedule(bpy.types.Operator):
                 new.enum_items = json.dumps(ifcopenshell.util.attribute.get_enum_items(attribute))
                 if data[attribute.name()]:
                     new.enum_value = data[attribute.name()]
-        props.active_work_schedule_id = self.work_schedule
-        bpy.ops.bim.load_tasks(work_schedule=self.work_schedule)
+        self.props.active_work_schedule_id = self.work_schedule
+
+        while len(self.props.tasks) > 0:
+            self.props.tasks.remove(0)
+
+        self.contracted_tasks = json.loads(self.props.contracted_tasks)
+        for related_object_id in Data.work_schedules[self.work_schedule]["RelatedObjects"]:
+            self.create_new_task_li(related_object_id, 0)
         return {"FINISHED"}
 
+    def create_new_task_li(self, related_object_id, level_index):
+        task = Data.tasks[related_object_id]
+        new = self.props.tasks.add()
+        new.name = task["Name"] or "Unnamed"
+        new.ifc_definition_id = related_object_id
+        new.is_expanded = related_object_id not in self.contracted_tasks
+        new.level_index = level_index
+        if task["RelatedObjects"]:
+            new.has_children = True
+            if new.is_expanded:
+                for related_object_id in task["RelatedObjects"]:
+                    self.create_new_task_li(related_object_id, level_index + 1)
+        # return {"FINISHED"}
+
 
 class DisableEditingWorkSchedule(bpy.types.Operator):
     bl_idname = "bim.disable_editing_work_schedule"
@@ -392,13 +396,80 @@ class DisableTaskEditingUI(bpy.types.Operator):
 class AddTask(bpy.types.Operator):
     bl_idname = "bim.add_task"
     bl_label = "Add Task"
+    task: bpy.props.IntProperty()
+
+    def execute(self, context):
+        props = context.scene.BIMWorkScheduleProperties
+        self.file = IfcStore.get_file()
+        ifcopenshell.api.run("sequence.add_task", self.file, **{
+        "parent_task": self.file.by_id(self.task)
+        })
+        Data.load(self.file)
+        bpy.ops.bim.enable_editing_work_schedule(work_schedule = props.active_work_schedule_id)
+        return {"FINISHED"}
+
+
+class AddSummaryTask(bpy.types.Operator):
+    bl_idname = "bim.add_summary_task"
+    bl_label = "Add Task"
     work_schedule: bpy.props.IntProperty()
 
     def execute(self, context):
+        props = context.scene.BIMWorkScheduleProperties
         self.file = IfcStore.get_file()
-        task = ifcopenshell.api.run("sequence.add_task", self.file)
-        control = self.file.by_id(self.work_schedule)
-        ifcopenshell.api.run("control.assign_control", self.file, related_object=task, relating_control=control)
+        ifcopenshell.api.run("sequence.add_task", self.file, **{
+        "work_schedule": self.file.by_id(self.work_schedule)
+        })
         Data.load(self.file)
-        bpy.ops.bim.enable_editing_work_schedule(work_schedule = self.work_schedule)
+        bpy.ops.bim.enable_editing_work_schedule(work_schedule = props.active_work_schedule_id)
+        return {"FINISHED"}
+
+
+class ExpandTask(bpy.types.Operator):
+    bl_idname = "bim.expand_task"
+    bl_label = "Expand Task"
+    task: bpy.props.IntProperty()
+
+    def execute(self, context):
+        props = context.scene.BIMWorkScheduleProperties
+        self.file = IfcStore.get_file()
+        contracted_tasks = json.loads(props.contracted_tasks)
+        contracted_tasks.remove(self.task)
+        props.contracted_tasks = json.dumps(contracted_tasks)
+        Data.load(self.file)
+        bpy.ops.bim.enable_editing_work_schedule(work_schedule = props.active_work_schedule_id)
+        return {"FINISHED"}
+
+
+class ContractTask(bpy.types.Operator):
+    bl_idname = "bim.contract_task"
+    bl_label = "Contract Task"
+    task: bpy.props.IntProperty()
+
+    def execute(self, context):
+        props = context.scene.BIMWorkScheduleProperties
+        self.file = IfcStore.get_file()
+        contracted_tasks = json.loads(props.contracted_tasks)
+        contracted_tasks.append(self.task)
+        props.contracted_tasks = json.dumps(contracted_tasks)
+        Data.load(self.file)
+        bpy.ops.bim.enable_editing_work_schedule(work_schedule = props.active_work_schedule_id)
+        return {"FINISHED"}
+
+
+class RemoveTask(bpy.types.Operator):
+    bl_idname = "bim.remove_task"
+    bl_label = "Remove Task"
+    task: bpy.props.IntProperty()
+
+    def execute(self, context):
+        props = context.scene.BIMWorkScheduleProperties
+        self.file = IfcStore.get_file()
+        ifcopenshell.api.run(
+            "sequence.remove_task",
+            self.file,
+            task=IfcStore.get_file().by_id(self.task),
+        )
+        Data.load(self.file)
+        bpy.ops.bim.enable_editing_work_schedule(work_schedule = props.active_work_schedule_id)
         return {"FINISHED"}
diff --git a/src/blenderbim/blenderbim/bim/module/sequence/prop.py b/src/blenderbim/blenderbim/bim/module/sequence/prop.py
index a21ec53a48..6d1d089537 100644
--- a/src/blenderbim/blenderbim/bim/module/sequence/prop.py
+++ b/src/blenderbim/blenderbim/bim/module/sequence/prop.py
@@ -17,7 +17,9 @@ class Task(PropertyGroup):
     name: StringProperty(name="Name")
     identification: StringProperty(name="Identification")
     ifc_definition_id: IntProperty(name="IFC Definition ID")
-
+    has_children: BoolProperty(name="Has Children")
+    is_expanded: BoolProperty(name="Is Expanded")
+    level_index: IntProperty(name="Level Index")
 
 class WorkPlan(PropertyGroup):
     name: StringProperty(name="Name")
@@ -32,19 +34,15 @@ class BIMWorkPlanProperties(PropertyGroup):
     active_work_plan_id: IntProperty(name="Active Work Plan Id")
 
 
-class WorkSchedule(PropertyGroup):
-    name: StringProperty(name="Name")
-    ifc_definition_id: IntProperty(name="IFC Definition ID")
-
-
 class BIMWorkScheduleProperties(PropertyGroup):
     work_schedule_attributes: CollectionProperty(name="Work Schedule Attributes", type=Attribute)
     is_editing: BoolProperty(name="Is Editing", default=False)
-    work_schedules: CollectionProperty(name="Work Schedules", type=WorkSchedule)
     active_work_schedule_index: IntProperty(name="Active Work Schedules Index")
     active_work_schedule_id: IntProperty(name="Active Work Schedules Id")
     tasks: CollectionProperty(name="Tasks", type=Task)
     active_task_index: IntProperty(name="Active Task Index")
+    contracted_tasks: StringProperty(name="Contracted Task Items", default="[]")
+
 
 
 class WorkCalendar(PropertyGroup):
diff --git a/src/blenderbim/blenderbim/bim/module/sequence/ui.py b/src/blenderbim/blenderbim/bim/module/sequence/ui.py
index d0eba710f5..54710c9621 100644
--- a/src/blenderbim/blenderbim/bim/module/sequence/ui.py
+++ b/src/blenderbim/blenderbim/bim/module/sequence/ui.py
@@ -80,31 +80,33 @@ class BIM_PT_work_schedules(Panel):
         return IfcStore.get_file()
 
     def draw(self, context):
+        self.props = context.scene.BIMWorkScheduleProperties
+
         if not Data.is_loaded:
             Data.load(IfcStore.get_file())
-        self.props = context.scene.BIMWorkScheduleProperties
+
         row = self.layout.row(align=True)
         row.label(text="{} Work Schedules Found".format(len(Data.work_schedules)), icon="TEXT")
-        if self.props.is_editing:
-            row.operator("bim.add_work_schedule", text="", icon="ADD")
-            row.operator("bim.disable_work_schedule_editing_ui", text="", icon="CHECKMARK")
-        else:
-            row.operator("bim.load_work_schedules", text="", icon="GREASEPENCIL")
+        row = self.layout.row()
+        row.operator("bim.add_work_schedule", icon="ADD")
 
-        if self.props.is_editing:
-            self.layout.template_list(
-                "BIM_UL_work_schedules",
-                "",
-                self.props,
-                "work_schedules",
-                self.props,
-                "active_work_schedule_index",
-            )
+        for work_schedule_id, work_schedule in Data.work_schedules.items():
+            row = self.layout.row(align=True)
+            row.label(text=work_schedule["Name"] or "Unnamed", icon="LINENUMBERS_ON")
 
-        if self.props.active_work_schedule_id:
-            self.draw_editable_ui(context)
+            if self.props.active_work_schedule_id and self.props.active_work_schedule_id == work_schedule_id:
+                row.operator("bim.edit_work_schedule", text="", icon="CHECKMARK")
+                row.operator("bim.disable_editing_work_schedule", text="", icon="X")
+            elif self.props.active_work_schedule_id:
+                row.operator("bim.remove_work_schedule", text="", icon="X").work_schedule = work_schedule_id
+            else:
+                row.operator("bim.enable_editing_work_schedule", text="", icon="GREASEPENCIL").work_schedule = work_schedule_id
+                row.operator("bim.remove_work_schedule", text="", icon="X").work_schedule = work_schedule_id
 
-    def draw_editable_ui(self, context):
+            if self.props.active_work_schedule_id == work_schedule_id:
+                self.draw_editable_work_schedule_ui(work_schedule_id, work_schedule)
+
+    def draw_editable_work_schedule_ui(self, work_schedule_id, work_schedule):
         for attribute in self.props.work_schedule_attributes:
             row = self.layout.row(align=True)
             if attribute.data_type == "string":
@@ -114,13 +116,9 @@ class BIM_PT_work_schedules(Panel):
             if attribute.is_optional:
                 row.prop(attribute, "is_null", icon="RADIOBUT_OFF" if attribute.is_null else "RADIOBUT_ON", text="")
 
-        self.draw_task_ui(context)
-
-    def draw_task_ui(self, context):
         row = self.layout.row(align=True)
-        row.label(text="{} Tasks Found".format(len(Data.tasks)), icon="ACTION")
-        row.operator("bim.add_task", text="", icon="ADD").work_schedule = self.props.active_work_schedule_id
-
+        row.label(text="X Summary Tasks")
+        row.operator("bim.add_summary_task", text="", icon="ADD").work_schedule = work_schedule_id
         self.layout.template_list(
             "BIM_UL_tasks",
             "",
@@ -130,21 +128,23 @@ class BIM_PT_work_schedules(Panel):
             "active_task_index",
         )
 
-
-class BIM_UL_work_schedules(UIList):
+class BIM_UL_tasks(UIList):
     def draw_item(self, context, layout, data, item, icon, active_data, active_propname):
         if item:
             row = layout.row(align=True)
-            row.label(text=item.name)
-            if context.scene.BIMWorkScheduleProperties.active_work_schedule_id == item.ifc_definition_id:
-                row.operator("bim.edit_work_schedule", text="", icon="CHECKMARK")
-                row.operator("bim.disable_editing_work_schedule", text="", icon="X")
-            elif context.scene.BIMWorkScheduleProperties.active_work_schedule_id:
-                row.operator("bim.remove_work_schedule", text="", icon="X").work_schedule = item.ifc_definition_id
+            for i in range(0, item.level_index):
+                row.label(text="", icon="BLANK1")
+            if item.has_children:
+                if item.is_expanded:
+                    row.operator("bim.contract_task", text="", emboss=False, icon="DISCLOSURE_TRI_DOWN").task = item.ifc_definition_id
+                else:
+                    row.operator("bim.expand_task", text="", emboss=False, icon="DISCLOSURE_TRI_RIGHT").task = item.ifc_definition_id
             else:
-                op = row.operator("bim.enable_editing_work_schedule", text="", icon="GREASEPENCIL")
-                op.work_schedule = item.ifc_definition_id
-                row.operator("bim.remove_work_schedule", text="", icon="X").work_schedule = item.ifc_definition_id
+                row.label(text="", icon="DOT")
+            row.label(text=item.name)
+            op = row.operator("bim.add_task", text="", icon="ADD")
+            op.task = item.ifc_definition_id
+            row.operator("bim.remove_task", text="", icon="X").task = item.ifc_definition_id
 
 
 class BIM_PT_work_calendars(Panel):
@@ -209,12 +209,3 @@ class BIM_UL_work_calendars(UIList):
                 op = row.operator("bim.enable_editing_work_calendar", text="", icon="GREASEPENCIL")
                 op.work_calendar = item.ifc_definition_id
                 row.operator("bim.remove_work_calendar", text="", icon="X").work_calendar = item.ifc_definition_id
-
-
-class BIM_UL_tasks(UIList):
-    def draw_item(self, context, layout, data, item, icon, active_data, active_propname):
-        if item:
-            row = layout.row(align=True)
-            if item.identification:
-                layout.label(text=item.identification)
-            layout.label(text=item.name)
diff --git a/src/blenderbim/blenderbim/bim/operator.py b/src/blenderbim/blenderbim/bim/operator.py
index 3851f1aff2..51eb123f52 100644
--- a/src/blenderbim/blenderbim/bim/operator.py
+++ b/src/blenderbim/blenderbim/bim/operator.py
@@ -67,9 +67,11 @@ class ExportIFC(bpy.types.Operator):
     filepath: bpy.props.StringProperty(subtype="FILE_PATH")
     json_version: bpy.props.EnumProperty(items=[("4", "4", ""), ("5a", "5a", "")], name="IFC JSON Version")
     json_compact: bpy.props.BoolProperty(name="Export Compact IFCJSON", default=False)
-    should_force_resave: bpy.props.BoolProperty(name="Resave .blend", default=False)
 
     def invoke(self, context, event):
+        if bpy.context.scene.BIMProperties.ifc_file:
+            self.filepath = bpy.context.scene.BIMProperties.ifc_file
+            return self.execute(context)
         if not self.filepath:
             self.filepath = bpy.path.ensure_ext(bpy.data.filepath, ".ifc")
         WindowManager = context.window_manager
@@ -104,8 +106,8 @@ class ExportIFC(bpy.types.Operator):
             new.name = output_file
         if not bpy.context.scene.BIMProperties.ifc_file:
             bpy.context.scene.BIMProperties.ifc_file = output_file
-        if self.should_force_resave:
-            bpy.ops.wm.save_as_mainfile(filepath=bpy.data.filepath)
+        if bpy.data.is_saved and bpy.data.is_dirty and bpy.data.filepath:
+            bpy.ops.wm.save_mainfile(filepath=bpy.data.filepath)
         return {"FINISHED"}
 
 
@@ -115,7 +117,6 @@ class ImportIFC(bpy.types.Operator, ImportHelper):
     filename_ext = ".ifc"
     filter_glob: bpy.props.StringProperty(default="*.ifc;*.ifczip;*.ifcxml", options={"HIDDEN"})
 
-    should_import_spaces: bpy.props.BoolProperty(name="Import Spaces", default=False)
     should_auto_set_workarounds: bpy.props.BoolProperty(name="Automatically Set Vendor Workarounds", default=True)
     should_use_cpu_multiprocessing: bpy.props.BoolProperty(name="Import with CPU Multiprocessing", default=True)
     should_merge_by_class: bpy.props.BoolProperty(name="Import and Merge by Class", default=False)
@@ -140,7 +141,6 @@ class ImportIFC(bpy.types.Operator, ImportHelper):
         )
 
         settings = import_ifc.IfcImportSettings.factory(context, self.filepath, logger)
-        settings.should_import_spaces = self.should_import_spaces
         settings.should_auto_set_workarounds = self.should_auto_set_workarounds
         settings.should_use_cpu_multiprocessing = self.should_use_cpu_multiprocessing
         settings.should_merge_by_class = self.should_merge_by_class
diff --git a/src/ifcopenshell-python/ifcopenshell/api/cost/remove_cost_item.py b/src/ifcopenshell-python/ifcopenshell/api/cost/remove_cost_item.py
new file mode 100644
index 0000000000..003cf31931
--- /dev/null
+++ b/src/ifcopenshell-python/ifcopenshell/api/cost/remove_cost_item.py
@@ -0,0 +1,10 @@
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"cost_item": None}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        # TODO: do a deep purge
+        self.file.remove(self.settings["cost_item"])
diff --git a/src/ifcopenshell-python/ifcopenshell/api/material/assign_material.py b/src/ifcopenshell-python/ifcopenshell/api/material/assign_material.py
index f7fc4be564..8e7147ee67 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/material/assign_material.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/material/assign_material.py
@@ -24,18 +24,28 @@ class Usecase:
         elif self.settings["type"] == "IfcMaterialProfileSet":
             material_set = self.file.create_entity(self.settings["type"])
             self.create_material_association(material_set)
+        elif self.settings["type"] == "IfcMaterialProfileSetUsage":
+            material_set = self.file.create_entity("IfcMaterialProfileSet")
+            material_set_usage = self.create_profile_set_usage(material_set)
+            self.create_material_association(material_set_usage)
         elif self.settings["type"] == "IfcMaterialList":
             material_set = self.file.create_entity(self.settings["type"])
             material_set.Materials = [self.settings["material"]]
             self.create_material_association(material_set)
 
     def create_layer_set_usage(self, material_set):
-        return self.file.create_entity("IfcMaterialLayerSetUsage", **{
-            "ForLayerSet": material_set,
-            "LayerSetDirection": "AXIS2" if self.settings["product"].is_a("IfcWall") else "AXIS3",
-            "DirectionSense": "POSITIVE",
-            "OffsetFromReferenceLine": 0
-        })
+        return self.file.create_entity(
+            "IfcMaterialLayerSetUsage",
+            **{
+                "ForLayerSet": material_set,
+                "LayerSetDirection": "AXIS2" if self.settings["product"].is_a("IfcWall") else "AXIS3",
+                "DirectionSense": "POSITIVE",
+                "OffsetFromReferenceLine": 0,
+            }
+        )
+
+    def create_profile_set_usage(self, material_set):
+        return self.file.create_entity("IfcMaterialProfileSetUsage", **{"ForProfileSet": material_set})
 
     def assign_ifc_material(self):
         rel = self.get_rel_associates_material(self.settings["material"])
diff --git a/src/ifcopenshell-python/ifcopenshell/api/material/data.py b/src/ifcopenshell-python/ifcopenshell/api/material/data.py
index 1c39d5b20f..6d1c68e5da 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/material/data.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/material/data.py
@@ -6,8 +6,10 @@ class Data:
     materials = {}
     constituent_sets = {}
     constituents = {}
+    layer_sets_usages = {}
     layer_sets = {}
     layers = {}
+    profile_set_usages = {}
     profile_sets = {}
     profiles = {}
     lists = {}
@@ -23,6 +25,7 @@ class Data:
         cls.layer_set_usages = {}
         cls.layer_sets = {}
         cls.layers = {}
+        cls.profile_set_usages = {}
         cls.profile_sets = {}
         cls.profiles = {}
         cls.lists = {}
@@ -41,6 +44,7 @@ class Data:
         cls.load_layers()
         cls.load_layer_usages()
         cls.load_profiles()
+        cls.load_profile_usages()
         cls.load_lists()
         cls.is_loaded = True
 
@@ -68,6 +72,11 @@ class Data:
         cls.layer_set_usages = {}
         cls.load_element("IfcMaterialLayerSetUsage", cls.layer_set_usages)
 
+    @classmethod
+    def load_profile_usages(cls):
+        cls.profile_set_usages = {}
+        cls.load_element("IfcMaterialProfileSetUsage", cls.profile_set_usages)
+
     @classmethod
     def load_profiles(cls):
         cls.profile_sets = {}
@@ -109,6 +118,4 @@ class Data:
     @classmethod
     def load_association(cls, association, product_id):
         material_select = association.RelatingMaterial
-        if material_select.is_a("IfcMaterialProfileSetUsage"):  # TODO: implement usages
-            material_select = material_select.ForProfileSet
         cls.products[product_id] = {"type": material_select.is_a(), "id": material_select.id()}
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/add_task.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/add_task.py
index e27acee45a..1102606064 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/sequence/add_task.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/add_task.py
@@ -1,16 +1,12 @@
 import ifcopenshell.api
-
+import ifcopenshell
 
 class Usecase:
     def __init__(self, file, **settings):
         self.file = file
         self.settings = {
-            "name": None,
-            "predefined_type": "NOTDEFINED",
-            "is_milestone": False,
-            "identification": "none",
-            "predecessor_to": None,
-            "successor_from": None,
+            "work_schedule": None,
+            "parent_task": None,
         }
         for key, value in settings.items():
             self.settings[key] = value
@@ -20,8 +16,23 @@ class Usecase:
             "root.create_entity",
             self.file,
             ifc_class="IfcTask",
-            predefined_type=self.settings["predefined_type"],
-            name=self.settings["name"],
+            name= None,
+            predefined_type= "NOTDEFINED",
+            identification= "none",
         )
-        task.IsMilestone = self.settings["is_milestone"]
+        task.IsMilestone = False
+        if self.settings["work_schedule"]:
+            self.file.create_entity(
+                "IfcRelAssignsToControl",
+                **{
+                    "GlobalId": ifcopenshell.guid.new(),
+                    "OwnerHistory": ifcopenshell.api.run("owner.create_owner_history", self.file),
+                    "RelatedObjects": [task],
+                    "RelatingControl": self.settings["work_schedule"],
+                }
+            )
+        elif self.settings["parent_task"]:
+            ifcopenshell.api.run(
+                "nest.assign_object", self.file, object=task, relating_object=self.settings["parent_task"]
+            )
         return task
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/data.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/data.py
index edfa8cbe45..04ba1e7a63 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/sequence/data.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/data.py
@@ -61,6 +61,7 @@ class Data:
 
     @classmethod
     def load_work_calendars(cls):
+        cls.work_calendars = {}
         for work_calendar in cls._file.by_type("IfcWorkCalendar"):
             data = work_calendar.get_info()
             del data["OwnerHistory"]
@@ -72,4 +73,9 @@ class Data:
     def load_tasks(cls):
         cls.tasks = {}
         for task in cls._file.by_type("IfcTask"):
-            cls.tasks[task.id()] = {"Name": task.Name, "Identification": task.Identification or ""}
+            data = task.get_info()
+            del data["OwnerHistory"]
+            data["RelatedObjects"] = []
+            for rel in task.IsNestedBy:
+                [data["RelatedObjects"].append(o.id()) for o in rel.RelatedObjects if o.is_a("IfcTask")]
+            cls.tasks[task.id()] = data
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_task.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_task.py
new file mode 100644
index 0000000000..941a335663
--- /dev/null
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_task.py
@@ -0,0 +1,19 @@
+import ifcopenshell.api
+
+
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"task": None}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        # TODO: do a deep purge
+        ifcopenshell.api.run(
+            "project.unassign_declaration",
+            self.file,
+            definition=self.settings["task"],
+            relating_context=self.file.by_type("IfcContext")[0],
+        )
+        self.file.remove(self.settings["task"])
diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_work_schedule.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_work_schedule.py
index c0af69b25d..2fd21d975f 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_work_schedule.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_work_schedule.py
@@ -1,3 +1,6 @@
+import ifcopenshell.api
+
+
 class Usecase:
     def __init__(self, file, **settings):
         self.file = file
diff --git a/src/ifcopenshell-python/ifcopenshell/util/element.py b/src/ifcopenshell-python/ifcopenshell/util/element.py
index 788acf7f34..1c90f3d391 100644
--- a/src/ifcopenshell-python/ifcopenshell/util/element.py
+++ b/src/ifcopenshell-python/ifcopenshell/util/element.py
@@ -119,17 +119,13 @@ def is_representation_of_context(representation, context, subcontext=None, targe
 
 
 def remove_deep(ifc_file, element):
+    # @todo maybe some sort of try-finally mechanism.
+    ifc_file.batch()
     subgraph = list(ifc_file.traverse(element))
     subgraph_set = set(subgraph)
     for ref in subgraph[::-1]:
         if ref.id() and len(set(ifc_file.get_inverse(ref)) - subgraph_set) == 0:
             ifc_file.remove(ref)
-
-
-def remove_deep_batched(ifc_file, element):
-    # @todo maybe some sort of try-finally mechanism.
-    ifc_file.batch()
-    remove_deep(ifc_file, element)
     ifc_file.unbatch()
 
 
diff --git a/src/ifcparse/IfcCharacterDecoder.cpp b/src/ifcparse/IfcCharacterDecoder.cpp
index 1c2fd38228..0ad9cc787d 100644
--- a/src/ifcparse/IfcCharacterDecoder.cpp
+++ b/src/ifcparse/IfcCharacterDecoder.cpp
@@ -317,7 +317,7 @@ IfcCharacterEncoder::operator std::string() {
 	// Either 2 or 4 to uses \X2 or \X4 respectively.
 	// Currently hardcoded to 4, but \X2 might be  
 	// sufficient for nearly all purposes.
-	const int num_bytes = *std::max_element(str.begin(), str.end()) > 0xffff ? 4 : 2;
+	const int num_bytes = (str.empty() || *std::max_element(str.begin(), str.end())) > 0xffff ? 4 : 2;
 	const std::string num_bytes_str = std::string(1,num_bytes + 0x30);
 		
 	bool in_extended = false;
diff --git a/src/ifcparse/IfcEntityInstanceData.h b/src/ifcparse/IfcEntityInstanceData.h
index 7d2c4ee8ca..6fb0386f38 100644
--- a/src/ifcparse/IfcEntityInstanceData.h
+++ b/src/ifcparse/IfcEntityInstanceData.h
@@ -48,17 +48,13 @@ public:
 		: file(file_), id_(id), type_(type), attributes_(0), offset_in_file_(offset_in_file)
 	{}
 
-	IfcEntityInstanceData(IfcParse::IfcFile* file_, size_t size)
-		: file(file_), id_(0), type_(0), attributes_(new Argument*[size]), offset_in_file_(0)
+   IfcEntityInstanceData(IfcParse::IfcFile* file_, size_t size)
+      : file(file_), id_(0), type_(0), attributes_(new Argument*[size] {0}), offset_in_file_(0)
 	{}
 
-	IfcEntityInstanceData(const IfcParse::declaration* type)
-		: file(0), id_(0), type_(type), attributes_(new Argument*[getArgumentCount()])
-	{
-		for (size_t i = 0; i < getArgumentCount(); ++i) {
-			attributes_[i] = 0;
-		}
-	}
+   IfcEntityInstanceData(const IfcParse::declaration* type)
+      : file(0), id_(0), type_(type), attributes_(new Argument*[getArgumentCount()]{ 0 }), offset_in_file_(0)
+   {}
 
 	void load() const;
 
diff --git a/src/ifcparse/IfcSpfHeader.cpp b/src/ifcparse/IfcSpfHeader.cpp
index 5b95e68dcf..779b717152 100644
--- a/src/ifcparse/IfcSpfHeader.cpp
+++ b/src/ifcparse/IfcSpfHeader.cpp
@@ -43,11 +43,6 @@ HeaderEntity::HeaderEntity(const char * const datatype, size_t size, IfcFile* fi
 	if (file) {
 		offset_in_file_ = file->stream->Tell();
 		load();
-	} else {
-		// attributes_ = new Argument*[size];
-		for (size_t i = 0; i < size; ++i) {
-			attributes_[i] = 0;
-		}
 	}
 }