diff -r 8e67c9f6da51 -r 2ab67fa1e78d server/src/main/webapp/js/model.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/server/src/main/webapp/js/model.js	Thu Aug 16 14:14:09 2012 +0200
@@ -0,0 +1,202 @@
+Rkns.Model = {}
+
+Rkns.Model._BaseElement = function(_project, _props) {
+    if (typeof _props !== "undefined") {
+        this._project = _project;
+        this.id = _props.id || Rkns.Utils.getUID(this.type);
+        this.title = _props.title || "(untitled " + this.type + ")";
+        this.description = _props.description || "";
+        this.uri = _props.uri || "";
+    }
+}
+
+Rkns.Model._BaseElement.prototype.addReference = function(_propName, _list, _id, _default) {
+    var _element = _list.getElement(_id);
+    if (typeof _element === "undefined" && typeof _default !== "undefined") {
+        this[ _propName ] = _default;
+        this[ _propName + "_id" ] = _default.id;
+    } else {
+        this[ _propName + "_id" ] = _id;
+        this[ _propName ] = _element;
+    }
+}
+
+Rkns.Model._BaseElement.prototype.updateGraphics = function() {
+    this._project.renderer.redraw();
+}
+
+Rkns.Model._BaseElement.prototype.updateData = function() {
+    this._project.serializer.save(this);
+}
+
+/* Element Class Generator */
+
+Rkns.Model._elementClass = function(_type) {
+    return Rkns.Utils.inherit(Rkns.Model._BaseElement, function() {
+        this.type = _type;
+    });
+}
+
+/* User Model */
+
+Rkns.Model.User = Rkns.Model._elementClass("user");
+
+Rkns.Model.User.prototype._init = function(_project, _props) {
+    this.color = _props.color || "#666666";
+}
+
+/* Node Model */
+
+Rkns.Model.Node = Rkns.Model._elementClass("node");
+
+Rkns.Model.Node.prototype._init = function(_project, _props) {
+    this.addReference("created_by", this._project.users, _props.created_by, _project.current_user);
+    this.position = _props.position;
+    this.description = _props.description || "";
+}
+
+Rkns.Model.Node.prototype.setPosition = function(_x, _y) {
+    if (typeof _x === "object") {
+        if (typeof _x.x !== "undefined" && typeof _x.y !== "undefined") {
+            this.position.x = _x.x;
+            this.position.y = _x.y;
+        } else {
+            if (typeof _x.length !== "undefined") {
+                this.position.x = _x[0];
+                this.position.y = _x[1];
+            }
+        }
+    } else {
+        if (typeof _y !== "undefined") {
+            this.position.x = +_x;
+            this.position.y = +_y;
+        }
+    }
+}
+
+/* Edge Model */
+
+Rkns.Model.Edge = Rkns.Model._elementClass("edge");
+
+Rkns.Model.Edge.prototype._init = function(_project, _props) {
+    this.addReference("created_by", this._project.users, _props.created_by, _project.current_user);
+    this.addReference("from", this._project.nodes, _props.from);
+    this.addReference("to", this._project.nodes, _props.to);
+}
+
+/* List Helper Functions -- See Metadataplayer */
+
+Rkns.Model.List = function() {
+    Array.call(this);
+    this.idIndex = [];
+}
+
+Rkns.Model.List.prototype = new Array();
+
+Rkns.Model.List.prototype.hasId = function(_id) {
+    return Rkns._(this.idIndex).include(_id);
+}
+
+Rkns.Model.List.prototype.getIds = function(_id) {
+    return this.idIndex;
+}
+
+/* On recent browsers, forEach and map are defined and do what we want.
+ * Otherwise, we'll use the Underscore.js functions
+ */
+if (typeof Array.prototype.forEach === "undefined") {
+    Rkns.Model.List.prototype.forEach = function(_callback) {
+        var _this = this;
+        Rkns._(this).forEach(function(_value, _key) {
+            _callback(_value, _key, _this);
+        });
+    }
+}
+
+if (typeof Array.prototype.map === "undefined") {
+    Rkns.Model.List.prototype.map = function(_callback) {
+        var _this = this;
+        return Rkns._(this).map(function(_value, _key) {
+            return _callback(_value, _key, _this);
+        });
+    }
+}
+
+/* We override Array's filter function because it doesn't return an Rkns.Model.List
+ */
+Rkns.Model.List.prototype.filter = function(_callback) {
+    var _this = this,
+        _res = new Rkns.Model.List();
+    _res.addElements(Rkns._(this).filter(function(_value, _key) {
+        return _callback(_value, _key, _this);
+    }));
+    return _res;
+}
+
+Rkns.Model.List.prototype.slice = function(_start, _end) {
+    var _res = new Rkns.Model.List();
+    _res.addElements(Array.prototype.slice.call(this, _start, _end));
+    return _res;
+}
+
+Rkns.Model.List.prototype.splice = function(_start, _end) {
+    var _res = new Rkns.Model.List();
+    _res.addElements(Array.prototype.splice.call(this, _start, _end));
+    this.idIndex.splice(_start, _end);
+    return _res;
+}
+
+/* Array has a sort function, but it's not as interesting as Underscore.js's sortBy
+ * and won't return a new Rkns.Model.List
+ */
+Rkns.Model.List.prototype.sortBy = function(_callback) {
+    var _this = this,
+        _res = new Rkns.Model.List();
+    _res.addElements(Rkns._(this).sortBy(function(_value, _key) {
+        return _callback(_value, _key, _this);
+    }));
+    return _res;
+}
+
+Rkns.Model.List.prototype.push = function(_el) {
+    if (typeof _el === "undefined" || typeof _el.id === "undefined") {
+        return;
+    }
+    var _index = (Rkns._(this.idIndex).indexOf(_el.id));
+    if (_index === -1) {
+        this.idIndex.push(_el.id);
+        Array.prototype.push.call(this, _el);
+    } else {
+        this[_index] = _el;
+    }
+}
+
+Rkns.Model.List.prototype.addElements = function(_array) {
+    var _this = this;
+    Rkns._(_array).forEach(function(_el) {
+        _this.push(_el);
+    });
+}
+
+Rkns.Model.List.prototype.removeId = function(_id) {
+    var _index = (Rkns._(this.idIndex).indexOf(_id));
+    if (_index !== -1) {
+        this.splice(_index,1);
+    }
+}
+
+Rkns.Model.List.prototype.removeIds = function(_list) {
+    var _this = this;
+    Rkns._(_list).forEach(function(_id) {
+        _this.removeId(_id);
+    });
+}
+
+Rkns.Model.List.prototype.getElement = function(_id) {
+    var _index = Rkns._(this.idIndex).indexOf(_id);
+    if (_index === -1) {
+        return undefined;
+    } else {
+        return this[_index];
+    }
+}