diff --git a/src/collection.js b/src/collection.js
new file mode 100644
index 000000000..4a980f37f
--- /dev/null
+++ b/src/collection.js
@@ -0,0 +1,116 @@
+// @todo Add events.
+
+var Collection = function (items) {
+	this.items = [];
+
+	this.next_id = 0;
+
+	if (items)
+	{
+		this.add(items);
+	}
+};
+util.inherits(Collection, EventEmitter);
+
+Collection.prototype.model = require('model');
+
+/**
+ * Adds new items to this collection.
+ */
+Collection.prototype.add = function (items) {
+	if (!_.isArray(items))
+	{
+		items = [items];
+	}
+
+	_.each(items, function (item) {
+		if ( !(item instanceof this.model) )
+		{
+			item = new this.model(item);
+		}
+
+		var error = item.validate();
+		if (undefined !== error)
+		{
+			// @todo Better system inspired by Backbone.js.
+			throw error;
+		}
+
+		var id = item.get('id');
+
+		if (undefined === id)
+		{
+			id = this.next_id++;
+			item.set('id', id);
+		}
+
+		// Existing items are ignored.
+		if (!this.items[id])
+		{
+			this.items[id] = item;
+		}
+	});
+};
+
+/**
+ * Removes items from this collection.
+ */
+Collection.prototype.remove = function (ids) {
+	if (!_.isArray(ids))
+	{
+		ids = [ids];
+	}
+
+	_.each(ids, function (id) {
+		delete this.items[id];
+	});
+};
+
+/**
+ * Updates existing items.
+ */
+Collection.prototype.update = function (items) {
+	if (!_.isArray(items))
+	{
+		items = [items];
+	}
+
+	_.each(items, function (item) {
+		if (item instanceof this.model)
+		{
+			item = item.properties;
+		}
+
+		// @todo
+		// var error = item.validate();
+		// if (undefined !== error)
+		// {
+		// 	// @todo Better system inspired by Backbone.js.
+		// 	throw error;
+		// }
+
+		var id = item.id;
+
+		// Missing items are ignored.
+		if (this.items[id])
+		{
+			this.items[id].set(item);
+		}
+	});
+};
+
+/**
+ * Smartly updates the collection.
+ *
+ * - Adds new items.
+ * - Updates existing items.
+ * - Removes missing items.
+ */
+Collection.prototype.set = function (items) {
+	throw 'not implemented';
+};
+
+Model.extend = require('extendable');
+
+// Export.
+module.exports = Model;
diff --git a/src/event-emitter.js b/src/event-emitter.js
new file mode 100644
index 000000000..60c6ed983
--- /dev/null
+++ b/src/event-emitter.js
@@ -0,0 +1,3 @@
+module.exports = require('events').EventEmitter;
+
+module.exports.extend = require('extendable');
diff --git a/src/model.js b/src/model.js
new file mode 100644
index 000000000..7ef7f0652
--- /dev/null
+++ b/src/model.js
@@ -0,0 +1,83 @@
+// @todo Add events.
+
+var Model = function (properties) {
+	this.properties = {};
+
+	if (properties)
+	{
+		this.set(properties);
+	}
+};
+util.inherits(Model, require('events').EventEmitter);
+
+/**
+ * Initializes the model after construction.
+ */
+Model.prototype.initialize = function () {};
+
+/**
+ * Validates the model.
+ *
+ * @returns {undefined|mixed} Returns something else than undefined if
+ *     there was an error.
+ */
+Model.prototype.validate = function (properties) {};
+
+/**
+ * Gets property.
+ */
+Model.prototype.get = function (property, def) {
+	var prop = this.properties[property];
+	if (undefined !== prop)
+	{
+		return prop;
+	}
+
+	prop = this['default'][property];
+	if (undefined !== prop)
+	{
+		return prop;
+	}
+
+	return def;
+};
+
+/**
+ * Checks if a property exists.
+ */
+Model.prototype.has = function (property) {
+	return (undefined !== this.get(property));
+};
+
+/**
+ * Sets properties.
+ */
+Model.prototype.set = function (properties, value) {
+	if (undefined !== value)
+	{
+		var property = properties;
+		properties = {};
+		properties[property] = value;
+	}
+
+	_.extend(this.properties, properties);
+};
+
+/**
+ * Unsets properties.
+ */
+Model.prototype.unset = function (properties) {
+	this.properties = _.omit(this.properties, properties);
+};
+
+/**
+ * Default properties.
+ *
+ * @type {Object}
+ */
+Model.prototype['default'] = {};
+
+Model.extend = require('extendable');
+
+// Export.
+module.exports = Model;
diff --git a/src/session.js b/src/session.js
new file mode 100644
index 000000000..c2502d600
--- /dev/null
+++ b/src/session.js
@@ -0,0 +1,5 @@
+module.exports = require('model').extend({
+	'close': function () {
+		session.emit('close');
+	},
+});