diff --git a/js/id/connection.js b/js/id/connection.js
index 0460b09ab..d2afa6281 100644
--- a/js/id/connection.js
+++ b/js/id/connection.js
@@ -124,7 +124,7 @@ iD.Connection = function() {
             }
         }
 
-        return iD.Graph(entities);
+        return entities;
     }
 
     function authenticated() {
diff --git a/js/id/graph/graph.js b/js/id/graph/graph.js
index 120fa2fe7..5e865b9ec 100644
--- a/js/id/graph/graph.js
+++ b/js/id/graph/graph.js
@@ -1,19 +1,30 @@
-iD.Graph = function(entities, mutable) {
-    if (!(this instanceof iD.Graph)) return new iD.Graph(entities, mutable);
+iD.Graph = function(other, mutable) {
+    if (!(this instanceof iD.Graph)) return new iD.Graph(other, mutable);
+
+    if (other instanceof iD.Graph) {
+        var base = other.base();
+        this.entities = _.assign(Object.create(base.entities), other.entities);
+        this._parentWays = _.assign(Object.create(base.parentWays), other._parentWays);
+        this._parentRels = _.assign(Object.create(base.parentRels), other._parentRels);
+        this.inherited = true;
 
-    if (_.isArray(entities)) {
-        this.entities = {};
-        for (var i = 0; i < entities.length; i++) {
-            this.entities[entities[i].id] = entities[i];
-        }
     } else {
-        this.entities = entities || {};
+        if (_.isArray(other)) {
+            var entities = {};
+            for (var i = 0; i < other.length; i++) {
+                entities[other[i].id] = other[i];
+            }
+            other = entities;
+        }
+        this.entities = Object.create({});
+        this._parentWays = Object.create({});
+        this._parentRels = Object.create({});
+        this.rebase(other || {});
     }
 
     this.transients = {};
-    this._parentWays = {};
-    this._parentRels = {};
     this._childNodes = {};
+    this.getEntity = _.bind(this.entity, this);
 
     if (!mutable) {
         this.freeze();
@@ -38,51 +49,21 @@ iD.Graph.prototype = {
     },
 
     parentWays: function(entity) {
-        var ent, id, parents;
-
-        if (!this._parentWays.calculated) {
-            for (var i in this.entities) {
-                ent = this.entities[i];
-                if (ent && ent.type === 'way') {
-                    for (var j = 0; j < ent.nodes.length; j++) {
-                        id = ent.nodes[j];
-                        parents = this._parentWays[id] = this._parentWays[id] || [];
-                        if (parents.indexOf(ent) < 0) {
-                            parents.push(ent);
-                        }
-                    }
-                }
-            }
-            this._parentWays.calculated = true;
-        }
-
-        return this._parentWays[entity.id] || [];
+        return _.map(this._parentWays[entity.id], this.getEntity);
     },
 
     isPoi: function(entity) {
-        return this.parentWays(entity).length === 0;
+        var parentWays = this._parentWays[entity.id];
+        return !parentWays || parentWays.length === 0;
+    },
+
+    isShared: function(entity) {
+        var parentWays = this._parentWays[entity.id];
+        return parentWays && parentWays.length > 1;
     },
 
     parentRelations: function(entity) {
-        var ent, id, parents;
-
-        if (!this._parentRels.calculated) {
-            for (var i in this.entities) {
-                ent = this.entities[i];
-                if (ent && ent.type === 'relation') {
-                    for (var j = 0; j < ent.members.length; j++) {
-                        id = ent.members[j].id;
-                        parents = this._parentRels[id] = this._parentRels[id] || [];
-                        if (parents.indexOf(ent) < 0) {
-                            parents.push(ent);
-                        }
-                    }
-                }
-            }
-            this._parentRels.calculated = true;
-        }
-
-        return this._parentRels[entity.id] || [];
+        return _.map(this._parentRels[entity.id], this.getEntity);
     },
 
     childNodes: function(entity) {
@@ -97,30 +78,132 @@ iD.Graph.prototype = {
         return (this._childNodes[entity.id] = nodes);
     },
 
-    merge: function(graph) {
-        return this.update(function () {
-            _.defaults(this.entities, graph.entities);
-        });
+    base: function() {
+        return {
+            'entities': iD.util.getPrototypeOf(this.entities),
+            'parentWays': iD.util.getPrototypeOf(this._parentWays),
+            'parentRels': iD.util.getPrototypeOf(this._parentRels)
+        };
+    },
+
+    // Unlike other graph methods, rebase mutates in place. This is because it
+    // is used only during the history operation that merges newly downloaded
+    // data into each state. To external consumers, it should appear as if the
+    // graph always contained the newly downloaded data.
+    rebase: function(entities) {
+        var base = this.base(),
+            i, k, child, id, keys;
+        // Merging of data only needed if graph is the base graph
+        if (!this.inherited) {
+            for (i in entities) {
+                if (!base.entities[i]) {
+                    base.entities[i] = entities[i];
+                    this._updateCalculated(undefined, entities[i],
+                            base.parentWays, base.parentRels);
+                }
+            }
+        }
+
+        keys = Object.keys(this._parentWays);
+        for (i = 0; i < keys.length; i++) {
+            child = keys[i];
+            if (base.parentWays[child]) {
+                for (k = 0; k < base.parentWays[child].length; k++) {
+                    id = base.parentWays[child][k];
+                    if (this.entity(id) && !_.contains(this._parentWays[child], id)) {
+                        this._parentWays[child].push(id);
+                    }
+                }
+            }
+        }
+
+        keys = Object.keys(this._parentRels);
+        for (i = 0; i < keys.length; i++) {
+            child = keys[i];
+            if (base.parentRels[child]) {
+                for (k = 0; k < base.parentRels[child].length; k++) {
+                    id = base.parentRels[child][k];
+                    if (this.entity(id) && !_.contains(this._parentRels[child], id)) {
+                        this._parentRels[child].push(id);
+                    }
+                }
+            }
+        }
+    },
+
+    // Updates calculated properties (parentWays, parentRels) for the specified change
+    _updateCalculated: function(oldentity, entity, parentWays, parentRels) {
+
+        parentWays = parentWays || this._parentWays;
+        parentRels = parentRels || this._parentRels;
+
+        var type = entity && entity.type || oldentity && oldentity.type,
+            removed, added, ways, rels, i;
+
+
+        if (type === 'way') {
+
+            // Update parentWays
+            if (oldentity && entity) {
+                removed = _.difference(oldentity.nodes, entity.nodes);
+                added = _.difference(entity.nodes, oldentity.nodes);
+            } else if (oldentity) {
+                removed = oldentity.nodes;
+                added = [];
+            } else if (entity) {
+                removed = [];
+                added = entity.nodes;
+            }
+            for (i = 0; i < removed.length; i++) {
+                parentWays[removed[i]] = _.without(parentWays[removed[i]], oldentity.id);
+            }
+            for (i = 0; i < added.length; i++) {
+                ways = _.without(parentWays[added[i]], entity.id);
+                ways.push(entity.id);
+                parentWays[added[i]] = ways;
+            }
+        } else if (type === 'node') {
+
+        } else if (type === 'relation') {
+
+            // Update parentRels
+            if (oldentity && entity) {
+                removed = _.difference(oldentity.members, entity.members);
+                added = _.difference(entity.members, oldentity);
+            } else if (oldentity) {
+                removed = oldentity.members;
+                added = [];
+            } else if (entity) {
+                removed = [];
+                added = entity.members;
+            }
+            for (i = 0; i < removed.length; i++) {
+                parentRels[removed[i].id] = _.without(parentRels[removed[i].id], oldentity.id);
+            }
+            for (i = 0; i < added.length; i++) {
+                rels = _.without(parentRels[added[i].id], entity.id);
+                rels.push(entity.id);
+                parentRels[added[i].id] = rels;
+            }
+        }
     },
 
     replace: function(entity) {
         return this.update(function () {
+            this._updateCalculated(this.entities[entity.id], entity);
             this.entities[entity.id] = entity;
         });
     },
 
     remove: function(entity) {
         return this.update(function () {
-            if (entity.created()) {
-                delete this.entities[entity.id];
-            } else {
-                this.entities[entity.id] = undefined;
-            }
+            this._updateCalculated(entity, undefined);
+            this.entities[entity.id] = undefined;
         });
     },
 
     update: function() {
-        var graph = this.frozen ? iD.Graph(_.clone(this.entities), true) : this;
+        var graph = this.frozen ? iD.Graph(this, true) : this;
 
         for (var i = 0; i < arguments.length; i++) {
             arguments[i].call(graph, graph);
@@ -133,7 +216,6 @@ iD.Graph.prototype = {
         this.frozen = true;
 
         if (iD.debug) {
-            Object.freeze(this);
             Object.freeze(this.entities);
         }
 
@@ -153,9 +235,12 @@ iD.Graph.prototype = {
     },
 
     difference: function (graph) {
-        var result = [], entity, oldentity, id;
+        var result = [],
+            keys = Object.keys(this.entities),
+            entity, oldentity, id, i;
 
-        for (id in this.entities) {
+        for (i = 0; i < keys.length; i++) {
+            id = keys[i];
             entity = this.entities[id];
             oldentity = graph.entities[id];
             if (entity !== oldentity) {
@@ -177,7 +262,9 @@ iD.Graph.prototype = {
             }
         }
 
-        for (id in graph.entities) {
+        keys = Object.keys(graph.entities);
+        for (i = 0; i < keys.length; i++) {
+            id = keys[i];
             entity = graph.entities[id];
             if (entity && !this.entities.hasOwnProperty(id)) {
                 result.push(id);
@@ -189,25 +276,25 @@ iD.Graph.prototype = {
     },
 
     modified: function() {
-        var result = [];
+        var result = [], base = this.base().entities;
         _.each(this.entities, function(entity, id) {
-            if (entity && entity.modified()) result.push(id);
+            if (entity && base[id]) result.push(id);
         });
         return result;
     },
 
     created: function() {
-        var result = [];
+        var result = [], base = this.base().entities;
         _.each(this.entities, function(entity, id) {
-            if (entity && entity.created()) result.push(id);
+            if (entity && !base[id]) result.push(id);
         });
         return result;
     },
 
     deleted: function() {
-        var result = [];
+        var result = [], base = this.base().entities;
         _.each(this.entities, function(entity, id) {
-            if (!entity) result.push(id);
+            if (!entity && base[id]) result.push(id);
         });
         return result;
     }
diff --git a/js/id/graph/history.js b/js/id/graph/history.js
index 29b652554..42e1b1604 100644
--- a/js/id/graph/history.js
+++ b/js/id/graph/history.js
@@ -29,9 +29,9 @@ iD.History = function() {
             return stack[index].graph;
         },
 
-        merge: function (graph) {
+        merge: function (entities) {
             for (var i = 0; i < stack.length; i++) {
-                stack[i].graph = stack[i].graph.merge(graph);
+                stack[i].graph.rebase(entities);
             }
         },
 
diff --git a/js/id/renderer/map.js b/js/id/renderer/map.js
index c7c1ed632..0d1532948 100644
--- a/js/id/renderer/map.js
+++ b/js/id/renderer/map.js
@@ -64,7 +64,7 @@ iD.Map = function() {
             for (var i = 0; i < parents.length; i++) {
                 var parent = parents[i];
                 if (only[parent.id] === undefined) {
-                    only[parent.id] = graph.entity(parent.id);
+                    only[parent.id] = parent;
                     addParents(graph.parentRelations(parent));
                 }
             }
@@ -123,7 +123,7 @@ iD.Map = function() {
 
     function connectionLoad(err, result) {
         history.merge(result);
-        redraw(Object.keys(result.entities));
+        redraw(Object.keys(result));
     }
 
     function zoomPan() {
@@ -165,7 +165,8 @@ iD.Map = function() {
     }
 
     function resetTransform() {
-        if (!surface.style(transformProp)) return false;
+        var prop = surface.style(transformProp);
+        if (!prop || prop === 'none') return false;
         surface.style(transformProp, '');
         tilegroup.style(transformProp, '');
         return true;
diff --git a/js/id/svg/vertices.js b/js/id/svg/vertices.js
index 06be536ec..ba28c968a 100644
--- a/js/id/svg/vertices.js
+++ b/js/id/svg/vertices.js
@@ -36,7 +36,7 @@ iD.svg.Vertices = function(projection) {
         groups.attr('transform', iD.svg.PointTransform(projection))
             .call(iD.svg.TagClasses())
             .call(iD.svg.MemberClasses(graph))
-            .classed('shared', function(entity) { return graph.parentWays(entity).length > 1; });
+            .classed('shared', function(entity) { return graph.isShared(entity); });
 
         // Selecting the following implicitly
         // sets the data (vertix entity) on the elements
diff --git a/js/id/ui/contributors.js b/js/id/ui/contributors.js
index c0036a677..c64d8a2ac 100644
--- a/js/id/ui/contributors.js
+++ b/js/id/ui/contributors.js
@@ -16,7 +16,7 @@ iD.ui.contributors = function(map) {
         var l = selection
             .select('.contributor-list')
             .selectAll('a.user-link')
-            .data(subset);
+            .data(subset, function(d) { return d; });
 
 
         l.enter().append('a')
@@ -43,6 +43,10 @@ iD.ui.contributors = function(map) {
                         ext[1][0], ext[1][1]];
                 })
                 .text(' and ' + (u.length - limit) + ' others');
+        } else {
+            selection
+                .select('.contributor-count')
+                .html('');
         }
 
         if (!u.length) {
diff --git a/js/id/util.js b/js/id/util.js
index da31a162b..645d15363 100644
--- a/js/id/util.js
+++ b/js/id/util.js
@@ -74,3 +74,5 @@ iD.util.getStyle = function(selector) {
         }
     }
 };
+
+iD.util.getPrototypeOf = Object.getPrototypeOf || function(obj) { return obj.__proto__; };
diff --git a/test/spec/connection.js b/test/spec/connection.js
index 2f5d93808..652c1419b 100644
--- a/test/spec/connection.js
+++ b/test/spec/connection.js
@@ -26,24 +26,24 @@ describe('iD.Connection', function () {
             c.loadFromURL('data/node.xml', done);
         });
 
-        it('returns a graph', function (done) {
+        it('returns an object', function (done) {
             c.loadFromURL('data/node.xml', function (err, graph) {
                 expect(err).to.not.be.ok;
-                expect(graph).to.be.instanceOf(iD.Graph);
+                expect(typeof graph).to.eql('object');
                 done();
             });
         });
 
         it('parses a node', function (done) {
             c.loadFromURL('data/node.xml', function (err, graph) {
-                expect(graph.entity('n356552551')).to.be.instanceOf(iD.Entity);
+                expect(graph.n356552551).to.be.instanceOf(iD.Entity);
                 done();
             });
         });
 
         it('parses a way', function (done) {
             c.loadFromURL('data/way.xml', function (err, graph) {
-                expect(graph.entity('w19698713')).to.be.instanceOf(iD.Entity);
+                expect(graph.w19698713).to.be.instanceOf(iD.Entity);
                 done();
             });
         });
diff --git a/test/spec/graph/graph.js b/test/spec/graph/graph.js
index 25382e7c9..327d66295 100644
--- a/test/spec/graph/graph.js
+++ b/test/spec/graph/graph.js
@@ -1,25 +1,164 @@
 describe('iD.Graph', function() {
-    it("can be constructed with an entities Object", function () {
-        var entity = iD.Entity(),
-            graph = iD.Graph({'n-1': entity});
-        expect(graph.entity('n-1')).to.equal(entity);
-    });
-
-    it("can be constructed with an entities Array", function () {
-        var entity = iD.Entity(),
-            graph = iD.Graph([entity]);
-        expect(graph.entity(entity.id)).to.equal(entity);
-    });
-
-    if (iD.debug) {
-        it("is frozen", function () {
-            expect(Object.isFrozen(iD.Graph())).to.be.true;
+    describe("constructor", function () {
+        it("accepts an entities Object", function () {
+            var entity = iD.Entity(),
+                graph = iD.Graph({'n-1': entity});
+            expect(graph.entity('n-1')).to.equal(entity);
         });
 
-        it("freezes entities", function () {
-            expect(Object.isFrozen(iD.Graph().entities)).to.be.true;
+        it("accepts an entities Array", function () {
+            var entity = iD.Entity(),
+                graph = iD.Graph([entity]);
+            expect(graph.entity(entity.id)).to.equal(entity);
         });
-    }
+
+        it("accepts a Graph", function () {
+            var entity = iD.Entity(),
+                graph = iD.Graph(iD.Graph([entity]));
+            expect(graph.entity(entity.id)).to.equal(entity);
+        });
+
+        it("copies other's entities", function () {
+            var entity = iD.Entity(),
+                base   = iD.Graph([entity]),
+                graph  = iD.Graph(base);
+            expect(graph.entities).not.to.equal(base.entities);
+        });
+
+        it("rebases on other's base", function () {
+            var base   = iD.Graph(),
+                graph  = iD.Graph(base);
+            expect(graph.base().entities).to.equal(base.base().entities);
+        });
+
+        it("freezes by default", function () {
+            expect(iD.Graph().frozen).to.be.true;
+        });
+
+        it("remains mutable if passed true as second argument", function () {
+            expect(iD.Graph([], true).frozen).not.to.be.true;
+        });
+    });
+
+    describe("#freeze", function () {
+        it("sets the frozen flag", function () {
+            expect(iD.Graph([], true).freeze().frozen).to.be.true;
+        });
+
+        if (iD.debug) {
+            it("freezes entities", function () {
+                expect(Object.isFrozen(iD.Graph().entities)).to.be.true;
+            });
+        }
+    });
+
+    describe("#rebase", function () {
+        it("preserves existing entities", function () {
+            var node = iD.Node({id: 'n'}),
+                graph = iD.Graph([node]);
+            graph.rebase({});
+            expect(graph.entity('n')).to.equal(node);
+        });
+
+        it("includes new entities", function () {
+            var node = iD.Node({id: 'n'}),
+                graph = iD.Graph();
+            graph.rebase({'n': node});
+            expect(graph.entity('n')).to.equal(node);
+        });
+
+        it("gives precedence to existing entities", function () {
+            var a = iD.Node({id: 'n'}),
+                b = iD.Node({id: 'n'}),
+                graph = iD.Graph([a]);
+            graph.rebase({'n': b});
+            expect(graph.entity('n')).to.equal(a);
+        });
+
+        it("inherits entities from base prototypally", function () {
+            var graph = iD.Graph();
+            graph.rebase({'n': iD.Node()});
+            expect(graph.entities).not.to.have.ownProperty('n');
+        });
+
+        it("updates parentWays", function () {
+            var n = iD.Node({id: 'n'}),
+                w1 = iD.Way({id: 'w1', nodes: ['n']}),
+                w2 = iD.Way({id: 'w2', nodes: ['n']}),
+                graph = iD.Graph([n, w1]);
+
+            graph.rebase({ 'w2': w2 });
+            expect(graph.parentWays(n)).to.eql([w1, w2]);
+            expect(graph._parentWays.hasOwnProperty('n')).to.be.false;
+        });
+
+        it("avoids adding duplicate parentWays", function () {
+            var n = iD.Node({id: 'n'}),
+                w1 = iD.Way({id: 'w1', nodes: ['n']}),
+                graph = iD.Graph([n, w1]);
+            graph.rebase({ 'w1': w1 });
+            expect(graph.parentWays(n)).to.eql([w1]);
+        });
+
+        it("updates parentWays for nodes with modified parentWays", function () {
+            var n = iD.Node({id: 'n'}),
+                w1 = iD.Way({id: 'w1', nodes: ['n']}),
+                w2 = iD.Way({id: 'w2', nodes: ['n']}),
+                w3 = iD.Way({id: 'w3', nodes: ['n']}),
+                graph = iD.Graph([n, w1]),
+                graph2 = graph.replace(w2);
+            graph.rebase({ 'w3': w3 });
+            graph2.rebase({ 'w3': w3 });
+
+            expect(graph2.parentWays(n)).to.eql([w1, w2, w3]);
+        });
+
+        it("avoids re-adding removed parentWays", function() {
+            var n = iD.Node({id: 'n'}),
+                w1 = iD.Way({id: 'w1', nodes: ['n']}),
+                graph = iD.Graph([n, w1]),
+                graph2 = graph.remove(w1);
+            graph.rebase({ 'w1': w1 });
+            graph2.rebase({ 'w1': w1 });
+            expect(graph2.parentWays(n)).to.eql([]);
+        });
+
+        it("updates parentRelations", function () {
+            var n = iD.Node({id: 'n'}),
+                r1 = iD.Relation({id: 'r1', members: [{id: 'n'}]}),
+                r2 = iD.Relation({id: 'r2', members: [{id: 'n'}]}),
+                graph = iD.Graph([n, r1]);
+
+            graph.rebase({'r2': r2});
+
+            expect(graph.parentRelations(n)).to.eql([r1, r2]);
+            expect(graph._parentRels.hasOwnProperty('n')).to.be.false;
+        });
+
+        it("avoids re-adding removed parentRels", function() {
+            var n = iD.Node({id: 'n'}),
+                r1 = iD.Relation({id: 'r1', members: [{id: 'n'}]}),
+                graph = iD.Graph([n, r1]),
+                graph2 = graph.remove(r1);
+            graph.rebase({ 'w1': r1 });
+            graph2.rebase({ 'w1': r1 });
+            expect(graph2.parentWays(n)).to.eql([]);
+        });
+
+        it("updates parentRels for nodes with modified parentWays", function () {
+            var n = iD.Node({id: 'n'}),
+                r1 = iD.Relation({id: 'r1', members: [{id: 'n'}]}),
+                r2 = iD.Relation({id: 'r2', members: [{id: 'n'}]}),
+                r3 = iD.Relation({id: 'r3', members: [{id: 'n'}]}),
+                graph = iD.Graph([n, r1]),
+                graph2 = graph.replace(r2);
+
+            graph.rebase({'r3': r3});
+            graph2.rebase({'r3': r3});
+            expect(graph2.parentRelations(n)).to.eql([r1, r2, r3]);
+        });
+
+    });
 
     describe("#remove", function () {
         it("returns a new graph", function () {
@@ -40,6 +179,20 @@ describe('iD.Graph', function() {
                 graph = iD.Graph([node]);
             expect(graph.remove(node).entity(node.id)).to.be.undefined;
         });
+
+        it("removes the entity as a parentWay", function () {
+            var node = iD.Node({id: 'n' }),
+                w1 = iD.Way({id: 'w', nodes: ['n']}),
+                graph = iD.Graph([node, w1]);
+            expect(graph.remove(w1).parentWays(node)).to.eql([]);
+        });
+
+        it("removes the entity as a parentRelation", function () {
+            var node = iD.Node({id: 'n' }),
+                r1 = iD.Relation({id: 'w', members: [{id: 'n' }]}),
+                graph = iD.Graph([node, r1]);
+            expect(graph.remove(r1).parentRelations(node)).to.eql([]);
+        });
     });
 
     describe("#replace", function () {
@@ -62,6 +215,49 @@ describe('iD.Graph', function() {
                 graph = iD.Graph([node1]);
             expect(graph.replace(node2).entity(node2.id)).to.equal(node2);
         });
+
+        it("adds parentWays",  function () {
+            var node = iD.Node({id: 'n' }),
+                w1 = iD.Way({id: 'w', nodes: ['n']}),
+                graph = iD.Graph([node]);
+            expect(graph.replace(w1).parentWays(node)).to.eql([w1]);
+        });
+
+        it("removes parentWays",  function () {
+            var node = iD.Node({id: 'n' }),
+                w1 = iD.Way({id: 'w', nodes: ['n']}),
+                graph = iD.Graph([node, w1]);
+            expect(graph.remove(w1).parentWays(node)).to.eql([]);
+        });
+
+        it("doesn't add duplicate parentWays",  function () {
+            var node = iD.Node({id: 'n' }),
+                w1 = iD.Way({id: 'w', nodes: ['n']}),
+                graph = iD.Graph([node, w1]);
+            expect(graph.replace(w1).parentWays(node)).to.eql([w1]);
+        });
+
+        it("adds parentRels",  function () {
+            var node = iD.Node({id: 'n' }),
+            r1 = iD.Relation({id: 'w', members: [{id: 'n'}]}),
+            graph = iD.Graph([node]);
+            expect(graph.replace(r1).parentRelations(node)).to.eql([r1]);
+        });
+
+        it("removes parentRelations",  function () {
+            var node = iD.Node({id: 'n' }),
+            r1 = iD.Relation({id: 'w', members: [{id: 'n'}]}),
+            graph = iD.Graph([node, r1]);
+            expect(graph.remove(r1).parentRelations(node)).to.eql([]);
+        });
+
+        it("doesn't add duplicate parentRelations",  function () {
+            var node = iD.Node({id: 'n' }),
+            r1 = iD.Relation({id: 'w', members: [{id: 'n'}]}),
+            graph = iD.Graph([node, r1]);
+            expect(graph.replace(r1).parentRelations(node)).to.eql([r1]);
+        });
+
     });
 
     describe("#update", function () {
@@ -159,18 +355,18 @@ describe('iD.Graph', function() {
 
     describe("#modified", function () {
         it("returns an Array of ids of modified entities", function () {
-            var node1 = iD.Node({id: 'n1', _updated: true}),
-                node2 = iD.Node({id: 'n2'}),
-                graph = iD.Graph([node1, node2]);
-            expect(graph.modified()).to.eql([node1.id]);
+            var node = iD.Node({id: 'n1'}),
+                node_ = iD.Node({id: 'n1'}),
+                graph = iD.Graph([node]).replace(node_);
+            expect(graph.modified()).to.eql([node.id]);
         });
     });
 
     describe("#created", function () {
         it("returns an Array of ids of created entities", function () {
-            var node1 = iD.Node({id: 'n-1', _updated: true}),
+            var node1 = iD.Node({id: 'n-1'}),
                 node2 = iD.Node({id: 'n2'}),
-                graph = iD.Graph([node1, node2]);
+                graph = iD.Graph([node2]).replace(node1);
             expect(graph.created()).to.eql([node1.id]);
         });
     });
@@ -185,7 +381,7 @@ describe('iD.Graph', function() {
 
         it("doesn't include created entities that were subsequently deleted", function () {
             var node = iD.Node(),
-                graph = iD.Graph([node]).remove(node);
+                graph = iD.Graph().replace(node).remove(node);
             expect(graph.deleted()).to.eql([]);
         });
     });
diff --git a/test/spec/graph/history.js b/test/spec/graph/history.js
index b59190c0f..dc685b446 100644
--- a/test/spec/graph/history.js
+++ b/test/spec/graph/history.js
@@ -153,17 +153,15 @@ describe("iD.History", function () {
 
         it("includes modified entities", function () {
             var node1 = iD.Node({id: "n1"}),
-                node2 = node1.update({}),
-                graph = iD.Graph([node1]);
-            history.merge(graph);
+                node2 = node1.update({});
+            history.merge({ n1: node1});
             history.perform(function (graph) { return graph.replace(node2); });
             expect(history.changes().modified).to.eql([node2]);
         });
 
         it("includes deleted entities", function () {
-            var node = iD.Node({id: "n1"}),
-                graph = iD.Graph([node]);
-            history.merge(graph);
+            var node = iD.Node({id: "n1"});
+            history.merge({ n1: node });
             history.perform(function (graph) { return graph.remove(node); });
             expect(history.changes().deleted).to.eql([node]);
         });
@@ -189,7 +187,7 @@ describe("iD.History", function () {
         it("is the sum of all types of changes", function() {
             var node1 = iD.Node({id: "n1"}),
                 node2 = iD.Node();
-            history.merge(iD.Graph([node1]));
+            history.merge({ n1: node1 });
             history.perform(function (graph) { return graph.remove(node1); });
             expect(history.numChanges()).to.eql(1);
             history.perform(function (graph) { return graph.replace(node2); });