diff --git a/src/www/syntax-editor/js/ast.js b/src/www/syntax-editor/js/ast.js
index 651f949cd..633bdc2b6 100644
--- a/src/www/syntax-editor/js/ast.js
+++ b/src/www/syntax-editor/js/ast.js
@@ -1,76 +1,3 @@
-/* --- Tree representation -------------------------------------------------- */
-function Node(value, children) {
-    this.value = value;
-    this.children = [];
-    if (children != undefined)
-        for (c in children)
-            this.children.push( new Node(children[c],[]) );
-    this.hasChildren = function(){
-        return this.children.length > 0;
-    }
-
-    // generic HOF for traversing tree
-    this.traverse = function(f) {
-        function visit(node) {
-            f(node);
-            for (i in node.children) {
-                visit(node.children[i]);
-            }
-        }
-        visit(this);
-    }
-}
-
-function Tree(value) {
-    this.root = new Node(value, []);
-
-    // add value as child of id
-    this.add = function(id, value, children) {
-        var x = this.find(id);
-        x.children.push( new Node(value, children) );
-    }
-
-    // set tree at given id to 
-    this.setSubtree = function(id, node) {
-        var x = this.find(id);
-        x.value = node.value;
-        x.children = node.children;
-    }
-
-    // id should be a list of child indices [0,1,0]
-    // or a string separated by commas "0,1,0"
-    this.find = function(_id) {
-        var id = undefined
-        switch (typeof _id) {
-        case "number": id = [_id]; break;
-        case "string": id = _id.split(","); break;
-        case "object": id = _id.get().slice(); break; // clone NodeID array
-        }
-        var node = this.root;
-        if (id[0] == 0) id.shift();
-        while (id.length>0 && node.children.length>0) {
-            node = node.children[id.shift()];
-        }
-        if (id.length>0)
-            return undefined;
-        return node;
-    }
-
-    // generic HOF for traversing tree
-    this.traverse = function(f) {
-        function visit(id, node) {
-            f(node);
-            for (i in node.children) {
-                var newid = new NodeID(id);
-                newid.add(parseInt(i));
-                visit(newid, node.children[i]);
-            }
-        }
-        visit(new NodeID(), this.root);
-    }
-
-}
-
 /* --- ID for a node in a tree ---------------------------------------------- */
 function NodeID(x) {
     this.id = new Array();
@@ -104,42 +31,110 @@ function NodeID(x) {
 }
 
 /* --- Abstract Syntax Tree (with state)------------------------------------- */
-function AST(fun, cat) {
 
-    function ASTNode(fun, cat) {
-        this.fun = fun;
-        this.cat = cat;
+function ASTNode(data) {
+    for(var d in data) this[d]=data[d];
+    this.children = [];
+    // if (children != undefined)
+    //     for (c in children) {
+    //         this.children.push( new ASTNode(children[c]) );
+    //     }
+    this.hasChildren = function(){
+        return this.children.length > 0;
     }
 
-    this.tree = new Tree(new ASTNode(fun, cat));
+    // generic HOF for traversing tree
+    this.traverse = function(f) {
+        function visit(node) {
+            f(node);
+            for (i in node.children) {
+                visit(node.children[i]);
+            }
+        }
+        visit(this);
+    }
+    
+}
+
+function AST(fun, cat) {
+
+    // local helper function for building ASTNodes
+    newNode = function(fun, cat) {
+        return new ASTNode({
+            "fun": fun,
+            "cat": cat,
+            "children": []
+        });
+    }
+
+    this.root = newNode(fun, cat);
+    
     this.current = new NodeID(); // current id in tree
 
     this.getFun = function() {
-        return this.tree.find(this.current).value.fun;
+        return this.find(this.current).fun;
     }
     this.setFun = function(f) {
-        this.tree.find(this.current).value.fun = f;
+        this.find(this.current).fun = f;
     }
     this.getCat = function() {
-        return this.tree.find(this.current).value.cat;
+        return this.find(this.current).cat;
     }
     this.setCat = function(c) {
-        this.tree.find(this.current).value.cat = c;
+        this.find(this.current).cat = c;
     }
 
+
     // Add a single fun at current node
     this.add = function(fun, cat) {
-        this.tree.add(this.current, new ASTNode(fun,cat));
+        this._add(this.current, newNode(fun,cat));
     }
-    
+
+    // add node as child of id
+    this._add = function(id, node) {
+        var x = this.find(id);
+        x.children.push(node);
+    }
+
     // Set entire subtree at current node
     this.setSubtree = function(node) {
-        this.tree.setSubtree(this.current, node);
+        this._setSubtree(this.current, node);
+    }
+    
+    // set tree at given id to 
+    this._setSubtree = function(id, node) {
+        var x = this.find(id);
+        for (var n in node) x[n] = node[n];
+
+        x.traverse(function(node){
+            if (!node.children) node.children=[];
+            // TODO: this doesn't work!
+            //node = new ASTNode(node);
+        })
+    }
+
+    // id should be a list of child indices [0,1,0]
+    // or a string separated by commas "0,1,0"
+    this.find = function(_id) {
+        var id = undefined
+        switch (typeof _id) {
+        case "number": id = [_id]; break;
+        case "string": id = _id.split(","); break;
+        case "object": id = _id.get().slice(); break; // clone NodeID array
+        }
+        var node = this.root;
+        if (id[0] == 0) id.shift();
+        while (id.length>0 && node.children.length>0) {
+            node = node.children[id.shift()];
+        }
+        if (id.length>0)
+            return undefined;
+        return node;
     }
     
     // Clear children of current node
     this.removeChildren = function() {
-        this.tree.find(this.current).children = [];
+        this.find(this.current).children = [];
     }
 
     // Move current ID to next hole
@@ -148,12 +143,12 @@ function AST(fun, cat) {
         
         // loop until we're at top
         while (id.get().length > 0) {
-            var node = this.tree.find(id);
+            var node = this.find(id);
 
             // first check children
             for (i in node.children) {
                 var child = node.children[i];
-                if (!child.value.fun) {
+                if (!child.fun) {
                     var newid = new NodeID(id);
                     newid.add(i);
                     this.current = newid;
@@ -171,16 +166,28 @@ function AST(fun, cat) {
         this.current.add(i);
     }
 
-    // 
+    // generic HOF for traversing tree
+    // this.traverse = function(f) {
+    //     this.root.traverse(f);
+    // }
     this.traverse = function(f) {
-        this.tree.traverse(f);
+        function visit(id, node) {
+            f(node);
+            for (i in node.children) {
+                var newid = new NodeID(id);
+                newid.add(parseInt(i));
+                visit(newid, node.children[i]);
+            }
+        }
+        visit(new NodeID(), this.root);
     }
 
     // Return tree as string
     this.toString = function() {
         var s = "";
         function visit(node) {
-            s += node.value.fun ? node.value.fun : "?" ;
+            s += node.fun ? node.fun : "?" ;
+//            if (!node.hasChildren())
             if (node.children.length == 0)
                 return;
             for (i in node.children) {
@@ -189,47 +196,9 @@ function AST(fun, cat) {
                 s += ")";
             }
         }
-        visit(this.tree.root);
+        visit(this.root);
         return s;
     }
 
-    // Parse AST string into node tree
-    this.parseTree = function(str) {
-
-        function trim(str) {
-            return str.trim().replace(/^\(\s*(.*)\s*\)$/, "$1");
-        }
-
-        function visit(node, str) {
-            var parts = [];
-            var ix_last = 0;
-            var par_cnt = 0;
-            for (i in str) {
-                if (str[i] == " ") {
-                    if (par_cnt == 0) {
-                        parts.push(trim(str.substring(ix_last, i)));
-                        ix_last = i;
-                    }
-                }
-                else if (str[i] == "(")
-                    par_cnt++;
-                else if (str[i] == ")")
-                    par_cnt--;
-            }
-            parts.push(trim(str.substring(ix_last)));
-
-            var fun = parts.shift();
-            var cat = null; // will be filled later
-
-            node.value = new ASTNode(fun, cat);
-            for (i in parts) {
-                node.children.push(new Node());
-                visit(node.children[i], parts[i]);
-            }
-        }
-        var tree = new Node();
-        visit(tree, str);
-        return tree;
-    }
 }
 
diff --git a/src/www/syntax-editor/js/editor.js b/src/www/syntax-editor/js/editor.js
index b0663b816..1f6a374b5 100644
--- a/src/www/syntax-editor/js/editor.js
+++ b/src/www/syntax-editor/js/editor.js
@@ -43,6 +43,21 @@ function Editor(server,opts) {
 
 }
 
+Editor.prototype.get_grammar_constructors=function(callback) {
+    var t = this;
+    var args = {
+        format: "json"
+    };
+    var cont = function(data){
+        t.grammar_constructors = data;
+        if (callback) callback();
+    };
+    var err = function(data){
+        alert("Error");
+    };
+    t.server.browse(args, cont, err);
+}
+
 /* --- API for getting and setting state ------------------------------------ */
 
 Editor.prototype.get_ast=function() {
@@ -59,7 +74,7 @@ Editor.prototype.change_grammar=function(grammar_info) {
     with(this) {
         grammar = grammar_info;
         local.startcat = null;
-        start_fresh();
+        get_grammar_constructors(bind(start_fresh,this));
     }
 }
 
@@ -164,8 +179,8 @@ Editor.prototype.redraw_tree=function() {
     function visit(container, id, node) {
         var container2 = empty_class("div", "node");
         var label =
-            ((node.value.fun) ? node.value.fun : "?") + " : " +
-            ((node.value.cat) ? node.value.cat : "?");
+            ((node.fun) ? node.fun : "?") + " : " +
+            ((node.cat) ? node.cat : "?");
         var current = id.equals(t.ast.current);
         var element = elem("a", {class:(current?"current":"")}, [text(label)]);
         element.onclick = function() {
@@ -183,7 +198,7 @@ Editor.prototype.redraw_tree=function() {
     }
     with(this) {
         clear(ui.tree);
-        visit(ui.tree, new NodeID(), ast.tree.root);
+        visit(ui.tree, new NodeID(), ast.root);
     }
 }
 
@@ -234,15 +249,13 @@ Editor.prototype.generate_random = function() {
         cat: t.ast.getCat(),
         limit: 1
     };
+    if (!args.cat) {
+        alert("Missing category at current node");
+        return;
+    }
     var cont = function(data){
-        // Build tree of just fun, then populate with cats
-        var tree = t.ast.parseTree(data[0].tree);
-        tree.traverse(function(node){
-            var info = t.lookup_fun(node.value.fun);
-            node.value.cat = info.cat;
-        });
-        t.ast.setSubtree(tree);
-        t.redraw_tree();
+        var tree = data[0].tree;
+        t.import_ast(tree);
     };
     var err = function(data){
         alert("Error");
@@ -250,11 +263,33 @@ Editor.prototype.generate_random = function() {
     server.get_random(args, cont, err);
 }
 
+// Import AST from string representation
+Editor.prototype.import_ast = function(abstr) {
+    var t = this;
+    var args = {
+        tree: abstr
+    };
+    var cont = function(tree){
+        // Build tree of just fun, then populate with cats
+        t.ast.setSubtree(tree);
+        t.ast.traverse(function(node){
+            var info = t.lookup_fun(node.fun);
+            node.cat = info.cat;
+        });
+        t.redraw_tree();
+        t.update_linearisation();
+    };
+    server.pgf_call("abstrjson", args, cont);
+}
+
 // Look up information for a function, hopefully from cache
 Editor.prototype.lookup_fun = function(fun) {
-    // TODO
+    var t = this;
+    var def = t.grammar_constructors.funs[fun].def;
+    var ix = def.lastIndexOf(" ");
+    var cat = def.substr(ix).trim();
     return {
-        cat: null
+        cat: cat
     }
 }
 
diff --git a/src/www/syntax-editor/js/editor_menu.js b/src/www/syntax-editor/js/editor_menu.js
index c5e2e9912..ded47f54e 100644
--- a/src/www/syntax-editor/js/editor_menu.js
+++ b/src/www/syntax-editor/js/editor_menu.js
@@ -37,8 +37,8 @@ function EditorMenu(editor,opts) {
     with(this.ui) {
 	appendChildren(this.container, [text(" Startcat: "),startcat_menu]);
         appendChildren(this.container, [text(" To: "), to_toggle, to_menu]);
-//        appendChildren(this.container, [clear_button, random_button]);
-        appendChildren(this.container, [clear_button]);
+        appendChildren(this.container, [clear_button, random_button]);
+        // appendChildren(this.container, [clear_button]);
         startcat_menu.onchange=bind(this.change_startcat,this);
         to_menu.onchange=bind(this.change_language,this);
     }