diff --git a/packages/pouchorm/README.md b/packages/pouchorm/README.md
new file mode 100644
index 0000000..5be06a5
--- /dev/null
+++ b/packages/pouchorm/README.md
@@ -0,0 +1,140 @@
+# PouchORM
+
+An ORM for PouchDB inspired by [Hood.ie](https://hood.ie/) and [Django](https://djangoproject.com)
+
+## Usage
+
+### Type Definition
+
+In a type definition class, specify a static `getUniqueID` method and optionally a static `validate`
+method.
+
+```js
+import { PouchDB } from 'pouchdb';
+import { TypeSpec } from 'PouchORM';
+
+class FileSpec extends TypeSpec {
+	static getUniqueID(doc) {
+		return doc.digest.substr(0, 16);
+	}
+
+	static validate(doc) {
+		const REQUIRED_PROPS = ['filename', 'size', 'digest'];
+		const missing_props = REQUIRED_PROPS.filter(prop => !doc.hasOwnProperty(prop));
+		if (missing_props) {
+			throw new ValidationError('FileType missing required props: ', missing_props);
+		}
+	}
+}
+
+export const FileType = PouchDB.registerType('File', FileSpec);
+```
+
+Document properties of a type are not directly defined but the type definition. Specific properties
+can be enforced by the `validate` method. The following properties are illegal:
+
+* starting with an underscore (\_) - these are used by PouchDB internally
+* starting with a double dollar-sign ($$) - these are reserved for future use by PouchORM. (Single
+  dollar-sign properties may be used for your implementation’s meta-data.)
+
+### Type Functions
+
+* `FileType.getOrCreate(obj)` - Try to save the passed object as a document. If it fails with a /409
+  Conflict/, look up the existing one and return it (ignoring differences between passed object and
+  the found object)
+
+  * /obj/ - an object containing a partial document including an `id` property
+  * _Returns_ a FileType instance
+
+* `FileType.find(idOrSelector, options)` - Find one or many records. Optionally return a
+  subscribeable that will fire events when the selection changes.
+
+  * /idOrSelector/
+    * if a string or number is passed, `find` will attempt to lookup the document with this as the
+      id.
+    * if an object is passed, it will be treated as a selector for a find query
+  * /options/ can have the following optional properties
+    * /index/ - specify a specific index to use with the passed selector
+    * /live/ - boolean (default /false/) return a subscribeable that will fire when the results of
+      the selector are updated.
+    * /…/ - other options will be passed to `db.changes()` when `live: true`
+  * _Returns_
+    * if `options.live` is /false/, an array of FileType instances will be returned
+    * if `options.live` is /true/, a subscribeable will be returned. Subscription callbacks will be
+      called when the results of /idOrSelector/ changes
+
+* `FileType.index(index, fields)` - Create a PouchDB
+  [Index](https://pouchdb.com/api.html#create_index) that can be used by `FileType.find` to sort on
+  non-ID fields
+
+  * /index/ - a string value that can optionally be provided to the options object of
+    `FileType.find`
+  * /fields/ - an array of field names for PouchDB to index on.
+  * _Returns_ void
+
+* `FileType.delete(id)` - Remove a document from the db
+
+  * /id/ - the id string of the document to be removed
+  * _Returns_ void
+
+* `FileType.subscribe(callback)` - subscribe to all FileType changes
+  * _Returns_ - a function that unsubscribes the passed callback when called.
+
+### Type Properties
+
+* `FileType.db` - the PouchDB database used by `FileType`
+* `FileType.name` - the type name passed to the `registerType` function
+* `FileType.prefix` - the prefix used on all document ids stored in PouchDB
+* `FileType.selector` - the PouchDB selector definition used by ‘subscribe’ and ‘find’
+
+### Instance Methods
+
+Creating a new instance is standard Javascript for any new instance:
+
+```js
+let note = new FileType({
+	filename: 'note.txt',
+	type: 'text/plain'
+});
+```
+
+* _static_ `note.getUniqueID(doc)` - You _must override_ this function in your type definition to
+  provide the id to be used for this document.
+
+  * /doc/ - an object representing the document. This could be an instance of the type or a bare
+    object with properties for this type.
+  * _Returns_ - a unique string value to be used as a document id
+
+* _static_ `note.validate()` - By default this does nothing. Optionally override it with a method
+  that throws exceptions when a document is invalid to block writing invalid data to the database.
+
+* `note.save()` - Calls `validate()` and then writes the document to the database.
+
+  * _Returns_ - a self-reference to the instance
+
+* `note.update(props, save=true)` - Update this instance
+
+  * /props/ - a deeply nested object that will be applied to this instance
+  * /save/ - a boolean to save this document after updating.
+  * _Returns_ - a self-reference to the instance
+
+* `note.addAttachment(name, blob)` - Add a named attachment to this instance.
+
+  * /name/ - the name used to reference the attachment
+  * /blob/ - a blob instance of the actual data
+  * _Returns_ - a self-reference to the instance
+
+* `note.getAttachment(name)` - Retrieve a named attachment from this instance.
+
+  * /name/ - the name of the attachment specified in `addAttachment`
+  * _Returns_ - a Blob instance of the attachment data
+
+* `note.removeAttachment(name)` - Remove a named attachment from this instance.
+
+  * /name/ - the name of the attachment specified in `addAttachment`
+  * _Returns_ -
+
+* `note.delete()` - Flag this document as `_deleted` == `true`. This will cause it to not show up in
+  `find` results. (_Note_: documents are left in the database in this state to allow for deletion to
+  be synced to other nodes. To truly remove documents,
+  [compact your database](https://pouchdb.com/api.html#compaction).)
diff --git a/packages/pouchorm/package.json b/packages/pouchorm/package.json
new file mode 100644
index 0000000..45eba91
--- /dev/null
+++ b/packages/pouchorm/package.json
@@ -0,0 +1,17 @@
+{
+	"name": "pouchorm",
+	"version": "1.0.0",
+	"description": "Document Abstraction Layer for PouchDB",
+	"main": "lib/index.js",
+	"jsnext:main": "src/index.js",
+	"files": ["dist", "lib", "src"],
+	"scripts": {
+		"test": "node ../../bin/runTests.js ./"
+	},
+	"author": "Timothy Farrell <tim@thecookiejar.me> (https://github.com/explorigin)",
+	"license": "Apache-2.0",
+	"dependencies": {
+		"frptools": "^3.1.0"
+	},
+	"devDependencies": {}
+}
diff --git a/packages/pouchorm/rollup.config.js b/packages/pouchorm/rollup.config.js
new file mode 100644
index 0000000..a832a0d
--- /dev/null
+++ b/packages/pouchorm/rollup.config.js
@@ -0,0 +1,21 @@
+import json from 'rollup-plugin-json';
+import babel from 'rollup-plugin-babel';
+
+const babelConfig = {
+	env: {
+		es6: true,
+		browser: true
+	},
+	plugins: [],
+	presets: ['es2015-rollup']
+};
+
+export default {
+	entry: 'src/index.js',
+	moduleName: 'pouchorm',
+	plugins: [json(), babel(babelConfig)],
+	output: {
+		format: 'umd',
+		file: 'dist/pouchorm.js'
+	}
+};
diff --git a/packages/pouchorm/spec/livearray.spec.js b/packages/pouchorm/spec/livearray.spec.js
new file mode 100644
index 0000000..f5d0eb8
--- /dev/null
+++ b/packages/pouchorm/spec/livearray.spec.js
@@ -0,0 +1,117 @@
+import { LiveArray } from '../src/livearray.js';
+import { pouchDocArrayHash } from '../src/utils.js';
+
+describe('A LiveArray', () => {
+	let fakePouch;
+	const selector = {};
+	const opts = {};
+
+	beforeEach(() => {
+		fakePouch = {
+			find: () => {},
+			changes: () => fakePouch,
+			on: () => fakePouch
+		};
+	});
+
+	it('returns a computed (subscribable).', () => {
+		const la = LiveArray(fakePouch, selector, opts);
+
+		expect(typeof la).toEqual('function');
+		expect(typeof la.subscribe).toEqual('function');
+
+		expect(JSON.stringify(la())).toEqual('[]');
+	});
+
+	it('has a "ready" subscribable that is fired once and subscribers cleared when the main subscribable has data for the first time.', () => {
+		let sub = null;
+
+		const db = {
+			changes: options => {
+				return db;
+			},
+			on: (eventName, callback) => {
+				if (eventName == 'change') {
+					sub = callback;
+				}
+				expect(['change', 'error'].indexOf(eventName) !== -1).toBeTruthy();
+				return db;
+			},
+			cancel: () => (sub = null),
+			find: async selector => {
+				return Promise.resolve({ docs: [{ _id: 234 }] });
+			}
+		};
+
+		const la = LiveArray(db, selector, opts);
+
+		return new Promise((resolve, reject) => {
+			const unsub = la.ready.subscribe(() => {
+				unsub();
+				resolve();
+			});
+		});
+	});
+
+	it('fires when data changes.', () => {
+		let state = 0;
+		const changes = {
+			234: { id: 234, deleted: false, doc: { _id: 234 } },
+			34: { id: 34, deleted: true, doc: { _id: 34 } },
+			4564565: { id: 4564565, deleted: false, doc: { _id: 4564565 } }
+		};
+		const changeKeys = Object.keys(changes);
+		let sub = null;
+
+		const db = {
+			changes: options => {
+				expect(state).toEqual(1);
+				expect(options.live).toEqual(true);
+				expect(options.since).toEqual('now');
+				expect(options.selector).toBe(selector);
+				return db;
+			},
+			on: (eventName, callback) => {
+				if (eventName == 'change') {
+					sub = callback;
+				}
+				expect(['change', 'error'].indexOf(eventName) !== -1).toBeTruthy();
+				return db;
+			},
+			cancel: () => (sub = null),
+			find: async selector => {
+				const doc = changes[parseInt(changeKeys[state - 1])];
+				state += 1;
+				if (doc === undefined || doc.deleted) {
+					return Promise.resolve({ docs: [] });
+				}
+				return Promise.resolve({ docs: [doc.doc] });
+			}
+		};
+
+		const la = LiveArray(db, selector, opts);
+		state = 1;
+
+		let innerState = 0;
+
+		return new Promise((resolve, reject) => {
+			const unsub = la.ready.subscribe(() => {
+				la.subscribe(data => {
+					if (data.length) {
+						expect(data[0]._id).toEqual(parseInt(changeKeys[innerState]));
+					}
+					innerState += 1;
+
+					resolve();
+				});
+
+				changeKeys.forEach(id => {
+					const doc = changes[parseInt(id)];
+					sub(doc);
+				});
+
+				unsub();
+			});
+		});
+	});
+});
diff --git a/packages/pouchorm/spec/pouchorm.spec.js b/packages/pouchorm/spec/pouchorm.spec.js
new file mode 100644
index 0000000..6c93e90
--- /dev/null
+++ b/packages/pouchorm/spec/pouchorm.spec.js
@@ -0,0 +1,7 @@
+import { PouchORM } from '../src/index.js';
+
+// describe('A PouchORM Document', () => {
+//     it('.', () => {
+//         expect().nothing();
+//     });
+// });
diff --git a/packages/pouchorm/spec/support/jasmine.json b/packages/pouchorm/spec/support/jasmine.json
new file mode 100644
index 0000000..b52c9e6
--- /dev/null
+++ b/packages/pouchorm/spec/support/jasmine.json
@@ -0,0 +1,7 @@
+{
+	"spec_dir": "spec",
+	"spec_files": ["**/*[sS]pec.js"],
+	"helpers": ["helpers/**/*.js"],
+	"stopSpecOnExpectationFailure": false,
+	"random": false
+}
diff --git a/packages/pouchorm/spec/watcher.spec.js b/packages/pouchorm/spec/watcher.spec.js
new file mode 100644
index 0000000..fc38e03
--- /dev/null
+++ b/packages/pouchorm/spec/watcher.spec.js
@@ -0,0 +1,148 @@
+import { Watcher } from '../src/watcher.js';
+
+describe('A watcher', () => {
+	const selector = {};
+	const opts = {};
+
+	it('initially does nothing.', () => {
+		const db = {
+			changes: () => fail('Watcher should not call changes until the first subscription.')
+		};
+
+		const w = Watcher(db, selector, opts);
+		expect().nothing();
+	});
+
+	it('calls PouchDB.change API on the first subscription.', () => {
+		let state = 0;
+		const db = {
+			changes: options => {
+				expect(state).toEqual(1);
+				expect(options.live).toEqual(true);
+				expect(options.since).toEqual('now');
+				expect(options.selector).toBe(selector);
+				return db;
+			},
+			on: (eventName, callback) => {
+				expect(['change', 'error'].indexOf(eventName) !== -1).toBeTruthy();
+				return db;
+			},
+			cancel: () => {}
+		};
+
+		const w = Watcher(db, selector, opts);
+		state = 1;
+		w(() => fail('Subscription callback should not be called until data changes.'));
+	});
+
+	it('cancels change subscription when the last subscriber unsubscribes', () => {
+		let state = 0;
+		const db = {
+			changes: options => {
+				expect(state).toEqual(1);
+				expect(options.live).toEqual(true);
+				expect(options.since).toEqual('now');
+				expect(options.selector).toBe(selector);
+				return db;
+			},
+			on: (eventName, callback) => {
+				expect(['change', 'error'].indexOf(eventName) !== -1).toBeTruthy();
+				return db;
+			},
+			cancel: () => {
+				expect(state).toEqual(2);
+				state = 3;
+			}
+		};
+
+		const w = Watcher(db, selector, opts);
+		state = 1;
+		const unsub = w(() => fail('Subscription callback should not be called until data changes.'));
+		state = 2;
+		unsub();
+		expect(state).toEqual(3);
+	});
+
+	it('passes change events to subscribers.', () => {
+		let state = 0;
+		const changes = {
+			234: { id: 234, deleted: false, doc: { _id: 234 } },
+			34: { id: 34, deleted: true, doc: { _id: 34 } },
+			4564565: { id: 4564565, deleted: false, doc: { _id: 4564565 } }
+		};
+		let sub = null;
+		const db = {
+			changes: options => {
+				expect(state).toEqual(1);
+				expect(options.live).toEqual(true);
+				expect(options.since).toEqual('now');
+				expect(options.selector).toBe(selector);
+				return db;
+			},
+			on: (eventName, callback) => {
+				if (eventName == 'change') {
+					sub = callback;
+				}
+				expect(['change', 'error'].indexOf(eventName) !== -1).toBeTruthy();
+				return db;
+			},
+			cancel: () => (sub = null)
+		};
+
+		const w = Watcher(db, selector, opts);
+		state = 1;
+		w((id, deleted, doc) => {
+			expect(changes.hasOwnProperty(id)).toBeTruthy();
+			expect(changes[id].doc).toBe(doc);
+			expect(changes[id].deleted).toEqual(deleted);
+		});
+
+		Object.values(changes).forEach(sub);
+	});
+
+	it('dumps subscribers when an error event happens.', () => {
+		let state = 0;
+		const changes = {
+			234: { id: 234, deleted: false, doc: { _id: 234 } },
+			34: { id: 34, deleted: true, doc: { _id: 34 } },
+			4564565: { id: 4564565, deleted: false, doc: { _id: 4564565 } }
+		};
+		let sub = null;
+		let errorSub = null;
+		const db = {
+			changes: options => {
+				expect(state).toEqual(1);
+				expect(options.live).toEqual(true);
+				expect(options.since).toEqual('now');
+				expect(options.selector).toBe(selector);
+				return db;
+			},
+			on: (eventName, callback) => {
+				if (eventName == 'change') {
+					sub = callback;
+				}
+				if (eventName == 'error') {
+					errorSub = callback;
+				}
+				expect(['change', 'error'].indexOf(eventName) !== -1).toBeTruthy();
+				return db;
+			},
+			cancel: () => {
+				sub = null;
+				errorSub = null;
+			}
+		};
+
+		const w = Watcher(db, selector, opts);
+		state = 1;
+		w(() => fail('Subscription callback should not be called until data changes.'));
+
+		const error = new Error('TestError');
+		try {
+			errorSub(error);
+		} catch (e) {
+			expect(e).toBe(error);
+		}
+		Object.values(changes).forEach(sub);
+	});
+});
diff --git a/packages/pouchorm/src/index.js b/packages/pouchorm/src/index.js
new file mode 100644
index 0000000..394e416
--- /dev/null
+++ b/packages/pouchorm/src/index.js
@@ -0,0 +1,3 @@
+import { isObject, deepAssign, pouchDocHash, pouchDocArrayHash } from './utils.js';
+export { TypeSpec } from './type.js';
+export { PouchORM } from './plugin.js';
diff --git a/packages/pouchorm/src/livearray.js b/packages/pouchorm/src/livearray.js
new file mode 100644
index 0000000..ca663b8
--- /dev/null
+++ b/packages/pouchorm/src/livearray.js
@@ -0,0 +1,47 @@
+import { prop, computed, id } from '../node_modules/frptools/src/index.js';
+
+import { Watcher } from './watcher.js';
+import { pouchDocArrayHash } from './utils.js';
+
+// LiveArray is a subscribable property function that always returns the db results that match
+// the provided selector and calls subscribers when the results change.
+export function LiveArray(db, selector, opts = {}) {
+	const mapper = opts.mapper || id;
+	opts.mapper && delete opts.mapper;
+	opts.include_docs = true;
+	const _watcher = Watcher(db, selector, opts);
+	let changeSub = null;
+
+	const ready = prop(false);
+	const data = prop({ docs: [] });
+	const docs = computed(r => r.docs.map(mapper), [data], pouchDocArrayHash);
+
+	const cleanup = () => {
+		docs.unsubscribeAll();
+		ready.unsubscribeAll();
+		if (changeSub) {
+			changeSub();
+			changeSub = null;
+		}
+		data({ docs: [] });
+	};
+
+	const refresh = async function refresh(...args) {
+		data(await db.find({ selector }));
+	};
+
+	docs.ready = ready;
+	docs.cleanup = cleanup;
+	docs.selector = selector;
+	docs.db = db;
+
+	refresh()
+		.then(() => {
+			changeSub = _watcher(refresh);
+			ready(true);
+		})
+		.then(() => {
+			ready.unsubscribeAll();
+		});
+	return docs;
+}
diff --git a/packages/pouchorm/src/plugin.js b/packages/pouchorm/src/plugin.js
new file mode 100644
index 0000000..af8ef41
--- /dev/null
+++ b/packages/pouchorm/src/plugin.js
@@ -0,0 +1,99 @@
+import { LiveArray } from './livearray.js';
+import { isObject } from './utils.js';
+
+export function PouchORM(PouchDB) {
+	PouchDB.registerType = (name, cls, db) => {
+		const prefix = name.toLowerCase();
+		const _db = db || PouchDB(prefix);
+		_db.setMaxListeners(1000);
+		const _baseSelector = Object.freeze({
+			_id: { $gt: `${prefix}_0`, $lt: `${prefix}_\ufff0` }
+		});
+		const watch = Watcher(_db, _baseSelector, { include_docs: true });
+
+		if (!cls.hasOwnProperty('validate')) {
+			warn(`${cls.name} has no validation.`);
+		}
+
+		const instantiate = doc => new cls(doc);
+
+		async function find(idOrSelector, opts = {}) {
+			if (typeof idOrSelector === 'string') {
+				return instantiate(await _db.get(idOrSelector));
+			}
+
+			const isSelector = isObject(idOrSelector);
+
+			const selector = Object.assign(
+				isSelector && idOrSelector._deleted ? { _deleted: true } : { _deleted: { exists: false } },
+				isSelector ? idOrSelector : _baseSelector
+			);
+			if (opts.index) {
+				opts.use_index = [prefix, opts.index];
+				delete opts.index;
+			}
+			if (opts.live) {
+				opts.mapper = instantiate;
+				return LiveArray(_db, idOrSelector, opts);
+			}
+			return (await _db.find(Object.assign({ selector: idOrSelector }, opts))).docs.map(instantiate);
+		}
+
+		async function getOrCreate(props) {
+			let doc = await new cls(props);
+			try {
+				await doc.save();
+			} catch (e) {
+				if (e.status !== 409) {
+					throw e;
+				}
+				doc = await find(doc._id);
+			}
+			return doc;
+		}
+
+		async function _delete(id) {
+			try {
+				const doc = await find(id);
+				doc._deleted = true;
+				await _db.put(doc);
+			} catch (e) {
+				if (e.status !== 404) {
+					throw e;
+				}
+			}
+		}
+
+		async function _index(name, fields) {
+			return _db.createIndex({
+				index: {
+					ddoc: prefix,
+					fields,
+					name
+				}
+			});
+		}
+
+		Object.defineProperties(cls.prototype, {
+			_name: { value: name },
+			_prefix: { value: prefix },
+			_db: { value: _db },
+			_cls: { value: cls },
+			_baseSelector: { value: _baseSelector }
+		});
+
+		Object.defineProperties(cls, {
+			getOrCreate: { value: getOrCreate },
+			find: { value: find },
+			index: { value: _index },
+			delete: { value: _delete },
+			subscribe: { value: watch },
+			db: { value: _db },
+			name: { value: name },
+			prefix: { value: prefix },
+			selector: { value: _baseSelector }
+		});
+
+		return cls;
+	};
+}
diff --git a/packages/pouchorm/src/type.js b/packages/pouchorm/src/type.js
new file mode 100644
index 0000000..8c210da
--- /dev/null
+++ b/packages/pouchorm/src/type.js
@@ -0,0 +1,69 @@
+import { pouchDocHash } from './utils.js';
+
+export class TypeSpec {
+	constructor(props) {
+		this._populateId(props);
+		Object.assign(this, { $links: {} }, props, { type: this._prefix });
+	}
+
+	static getUniqueID(doc) {
+		throw 'NotImplemented';
+	}
+
+	static validate(doc) {}
+
+	instantiate(doc) {
+		return new this._cls(docs);
+	}
+
+	_populateId(doc) {
+		if (!doc._id) {
+			doc._id = `${this._prefix}_${this._cls.getUniqueID(doc)}`;
+		}
+		return doc;
+	}
+
+	_hash() {
+		return pouchDocHash(this);
+	}
+
+	async delete() {
+		return await this.update({ _deleted: true });
+	}
+
+	async save() {
+		this._cls.validate(this);
+		const { rev } = await this._db.put(this);
+		this._rev = rev;
+		return this;
+	}
+
+	async addAttachment(attName, dataBlob) {
+		const { rev } = await this._db.putAttachment(
+			this._id,
+			attName,
+			this._rev,
+			dataBlob,
+			dataBlob.type
+		);
+
+		this._rev = rev;
+		return this;
+	}
+
+	async getAttachment(attName) {
+		return await this._db.getAttachment(this._id, attName);
+	}
+
+	async removeAttachment(attName) {
+		return await this._db.removeAttachment(this._id, attName, this._rev);
+	}
+
+	async update(props, save = true) {
+		deepAssign(this, props);
+		if (save) {
+			await this.save();
+		}
+		return this;
+	}
+}
diff --git a/packages/pouchorm/src/utils.js b/packages/pouchorm/src/utils.js
new file mode 100644
index 0000000..a398627
--- /dev/null
+++ b/packages/pouchorm/src/utils.js
@@ -0,0 +1,23 @@
+export function deepAssign(to, ...rest) {
+	for (let src of rest) {
+		for (let prop in src) {
+			const value = src[prop];
+			if (typeof value === 'object' && !Array.isArray(value)) {
+				to[prop] = deepAssign(to[prop] || {}, value);
+			} else if (value === undefined && to[prop] !== undefined) {
+				delete to[prop];
+			} else {
+				to[prop] = value;
+			}
+		}
+	}
+	return to;
+}
+
+export const pouchDocHash = d => (isObject(d) ? `${d._id}:${d._rev}` : d);
+export const pouchDocArrayHash = arr =>
+	Array.isArray(arr) ? arr.map(pouchDocHash).join('?') : arr;
+
+export function isObject(obj) {
+	return typeof obj === 'object' && !Array.isArray(obj) && obj !== null;
+}
diff --git a/packages/pouchorm/src/watcher.js b/packages/pouchorm/src/watcher.js
new file mode 100644
index 0000000..52463c4
--- /dev/null
+++ b/packages/pouchorm/src/watcher.js
@@ -0,0 +1,37 @@
+export function Watcher(db, selector, opts) {
+	const subscribers = new Set();
+	let changes = null;
+
+	return function subscribe(fn) {
+		subscribers.add(fn);
+
+		if (subscribers.size === 1 && !changes) {
+			changes = db
+				.changes(
+					Object.assign(
+						{
+							since: 'now',
+							live: true,
+							selector
+						},
+						opts
+					)
+				)
+				.on('change', change => {
+					const { id, deleted, doc } = change;
+					subscribers.forEach(s => s(id, !!deleted, doc));
+				})
+				.on('error', err => {
+					subscribers.clear();
+					throw err;
+				});
+		}
+		return () => {
+			subscribers.delete(fn);
+			if (subscribers.size === 0 && changes) {
+				changes.cancel();
+				changes = null;
+			}
+		};
+	};
+}