diff --git a/plugin/src/InstanceMap.lua b/plugin/src/InstanceMap.lua
index 59eccc80..25a25493 100644
--- a/plugin/src/InstanceMap.lua
+++ b/plugin/src/InstanceMap.lua
@@ -5,6 +5,7 @@ local Log = require(script.Parent.Parent.Log)
 	keep track of every instance we know about.
 
 	TODO: Track ancestry to catch when stuff moves?
+	TODO: Ability to pause change tracking for preventing feedback.
 ]]
 local InstanceMap = {}
 InstanceMap.__index = InstanceMap
diff --git a/plugin/src/PatchSet.lua b/plugin/src/PatchSet.lua
new file mode 100644
index 00000000..6d18b46d
--- /dev/null
+++ b/plugin/src/PatchSet.lua
@@ -0,0 +1,25 @@
+--[[
+	Methods to operate on either a patch created by the hydrate method, or a
+	patch returned from the API.
+]]
+
+local t = require(script.Parent.Parent.t)
+
+local Types = require(script.Parent.Types)
+
+local PatchSet = {}
+
+PatchSet.validate = t.interface({
+	removed = t.array(t.union(Types.RbxId, t.Instance)),
+	added = t.map(Types.RbxId, Types.ApiInstance),
+	updated = t.array(Types.ApiInstanceUpdate),
+})
+
+--[[
+	Invert the given PatchSet using the given instance map.
+]]
+function PatchSet.invert(patchSet, instanceMap)
+	error("not yet implemented", 2)
+end
+
+return PatchSet
\ No newline at end of file
diff --git a/plugin/src/Reconciler.lua b/plugin/src/Reconciler.lua
index 6050a401..ad395abf 100644
--- a/plugin/src/Reconciler.lua
+++ b/plugin/src/Reconciler.lua
@@ -5,24 +5,12 @@
 
 local RbxDom = require(script.Parent.Parent.RbxDom)
 local t = require(script.Parent.Parent.t)
-local Log = require(script.Parent.Parent.Log)
 
 local Types = require(script.Parent.Types)
 local invariant = require(script.Parent.invariant)
 local getCanonicalProperty = require(script.Parent.getCanonicalProperty)
 local setCanonicalProperty = require(script.Parent.setCanonicalProperty)
-
---[[
-	This interface represents either a patch created by the hydrate method, or a
-	patch returned from the API.
-
-	This type should be a subset of Types.ApiInstanceUpdate.
-]]
-local IPatch = t.interface({
-	removed = t.array(t.union(Types.RbxId, t.Instance)),
-	added = t.map(Types.RbxId, Types.ApiInstance),
-	updated = t.array(Types.ApiInstanceUpdate),
-})
+local PatchSet = require(script.Parent.PatchSet)
 
 --[[
 	Attempt to safely set the parent of an instance.
@@ -86,7 +74,7 @@ end
 	editable by scripts.
 ]]
 local applyPatchSchema = Types.ifEnabled(t.tuple(
-	IPatch
+	PatchSet.validate
 ))
 function Reconciler:applyPatch(patch)
 	assert(applyPatchSchema(patch))
@@ -287,7 +275,7 @@ local hydrateSchema = Types.ifEnabled(t.tuple(
 	t.map(Types.RbxId, Types.VirtualInstance),
 	Types.RbxId,
 	t.Instance,
-	IPatch
+	PatchSet.validate
 ))
 function Reconciler:__hydrateInternal(apiInstances, id, instance, hydratePatch)
 	assert(hydrateSchema(apiInstances, id, instance, hydratePatch))
diff --git a/plugin/src/ServeSession.lua b/plugin/src/ServeSession.lua
index bf6e9194..e527cc6d 100644
--- a/plugin/src/ServeSession.lua
+++ b/plugin/src/ServeSession.lua
@@ -4,7 +4,6 @@ local Log = require(script.Parent.Parent.Log)
 local Fmt = require(script.Parent.Parent.Fmt)
 local t = require(script.Parent.Parent.t)
 
-local DevSettings = require(script.Parent.DevSettings)
 local InstanceMap = require(script.Parent.InstanceMap)
 local Reconciler = require(script.Parent.Reconciler)
 local strict = require(script.Parent.strict)
diff --git a/plugin/src/getCanonicalProperty.lua b/plugin/src/getCanonicalProperty.lua
index 288d5989..f594722a 100644
--- a/plugin/src/getCanonicalProperty.lua
+++ b/plugin/src/getCanonicalProperty.lua
@@ -1,7 +1,7 @@
 local RbxDom = require(script.Parent.Parent.RbxDom)
 
 --[[
-	Attempts to set a property on the given instance.
+	Attempts to read a property from the given instance.
 ]]
 local function getCanonincalProperty(instance, propertyName)
 	local descriptor = RbxDom.findCanonicalPropertyDescriptor(instance.ClassName, propertyName)