raising events appears to work. nondeterminism currently ignored

src/App/App.tsx

@@ -1,19 +1,13 @@
 import { useState } from "react";
 
-import { ConcreteState, emptyStatechart, Statechart, Transition } from "../VisualEditor/ast";
+import { ConcreteState, emptyStatechart, Statechart, stateDescription, Transition } from "../VisualEditor/ast";
-
 import { VisualEditor } from "../VisualEditor/VisualEditor";
 import { RT_Statechart } from "../VisualEditor/runtime_types";
-import { initialize, raiseEvent } from "../VisualEditor/interpreter";
+import { initialize, handleEvent } from "../VisualEditor/interpreter";
+import { Action, Expression } from "../VisualEditor/label_ast";
 
 import "../index.css";
 import "./App.css";
-import { Action, Expression } from "../VisualEditor/label_ast";
-
-export function stateDescription(state: ConcreteState) {
-  const description = state.comments.length > 0 ? state.comments[0][1] : state.uid;
-  return description;
-}
 
 export function ShowTransition(props: {transition: Transition}) {
   return <>&#10132; {stateDescription(props.transition.tgt)}</>;
@@ -51,34 +45,22 @@ export function AST(props: {root: ConcreteState, transitions: Map<string, Transi
     <summary>{props.root.kind}: {description}</summary>
 
     {props.root.entryActions.length>0 &&
-      <details open={true}>
+        props.root.entryActions.map(action =>
-        <summary>entry actions</summary>
+          <div>&emsp;entry / <ShowAction action={action}/></div>
-        {props.root.entryActions.map(action =>
+        )
-          <div>&emsp;<ShowAction action={action}/></div>
-        )}
-      </details>
     }
     {props.root.exitActions.length>0 &&
-      <details open={true}>
+        props.root.exitActions.map(action =>
-        <summary>exit actions</summary>
+          <div>&emsp;exit / <ShowAction action={action}/></div>
-        {props.root.exitActions.map(action =>
+        )
-          <ShowAction action={action}/>
-        )}
-      </details>
     }
     {props.root.children.length>0 &&
-      <details open={true}>
+          props.root.children.map(child => 
-        <summary>children</summary>
-          {props.root.children.map(child => 
             <AST root={child} transitions={props.transitions} />
-          )}
+          )
-      </details>
     }
     {outgoing.length>0 &&
-      <details open={true}>
+        outgoing.map(transition => <>&emsp;<ShowTransition transition={transition}/><br/></>)
-        <summary>outgoing</summary>
-        {outgoing.map(transition => <>&emsp;<ShowTransition transition={transition}/><br/></>)}
-      </details>
     }
   </details>
 }
@@ -104,14 +86,15 @@ export function App() {
 
   function raise(event: string) {
     if (rt && ast.inputEvents.has(event)) {
-      const nextConfigs = raiseEvent(event, ast, ast.root, rt)
+      const nextConfig = handleEvent(event, ast, ast.root, rt);
-      console.log({nextConfigs});
+      setRT(nextConfig);
-      if (nextConfigs.length > 0) {
+      // console.log({nextConfigs});
-        if (nextConfigs.length > 1) {
+      // if (nextConfigs.length > 0) {
-          console.warn('non-determinism, blindly selecting first next run-time state!');
+      //   if (nextConfigs.length > 1) {
-        }
+      //     console.warn('non-determinism, blindly selecting first next run-time state!');
-        setRT(nextConfigs[0]);
+      //   }
-      }
+      //   setRT(nextConfigs[0]);
+      // }
     }
   }
 
@@ -126,9 +109,9 @@ export function App() {
       </select>
       <button onClick={stop} >stop</button>
       &emsp;
-      <input type="radio" name="paused" id="radio-paused" checked={paused} disabled={rt===null}/>
+      <input type="radio" name="paused" id="radio-paused" checked={paused} disabled={rt===null} onChange={e => setPaused(e.target.checked)}/>
       <label htmlFor="radio-paused">paused</label>
-      <input type="radio" name="realtime" id="radio-realtime" checked={!paused} disabled={rt===null}/>
+      <input type="radio" name="realtime" id="radio-realtime" checked={!paused} disabled={rt===null} onChange={e => setPaused(!e.target.checked)}/>
       <label htmlFor="radio-realtime">real-time</label>
       &emsp;
       <label htmlFor="number-timescale">timescale</label>

src/VisualEditor/VisualEditor.css

@@ -60,7 +60,7 @@ text.highlight {
 }
 .rountangle.active {
   fill: rgb(255, 196, 0);
-  fill-opacity: 0.6;
+  fill-opacity: 0.2;
 }
 
 .selected:hover {

src/VisualEditor/VisualEditor.tsx

@@ -9,9 +9,8 @@ import { parseStatechart } from "./parser";
 import { CORNER_HELPER_OFFSET, CORNER_HELPER_RADIUS, MIN_ROUNTANGLE_SIZE, ROUNTANGLE_RADIUS } from "./parameters";
 
 import * as lz4 from "@nick/lz4";
-import { getActiveStates, initialize } from "./interpreter";
 import { RT_Statechart } from "./runtime_types";
-import { emptyStatechart, Statechart } from "./ast";
+import { Statechart } from "./ast";
 
 
 type DraggingState = {
@@ -401,6 +400,11 @@ export function VisualEditor({ast, setAST, rt, setRT, errors, setErrors}: Visual
           ...state.texts.map(t => ({uid: t.uid, parts: ["text"]})),
         ]);
       }
+
+      if (e.key === "c") {
+        // e.preventDefault();
+        // setClipboard()
+      }
     }
   };
 
@@ -496,7 +500,7 @@ export function VisualEditor({ast, setAST, rt, setRT, errors, setErrors}: Visual
     }
   }
 
-  const active = getActiveStates(rt?.mode || {});
+  const active = rt?.mode || new Set();
 
   const rootErrors = errors.filter(([uid]) => uid === "root").map(err=>err[1]);
 

src/VisualEditor/actionlang_interpreter.ts

@@ -0,0 +1,46 @@
+// Just a simple recursive interpreter for the action language
+
+import { Expression } from "./label_ast";
+import { Environment } from "./runtime_types";
+
+
+const UNARY_OPERATOR_MAP: Map<string, (x: any) => any> = new Map([
+  ["!", x => !x],
+  ["-", x => -x as any],
+]);
+const BINARY_OPERATOR_MAP: Map<string, (a: any, b: any) => any> = new Map([
+  ["+", (a, b) => a + b],
+  ["-", (a, b) => a - b],
+  ["*", (a, b) => a * b],
+  ["/", (a, b) => a / b],
+  ["&&", (a, b) => a && b],
+  ["||", (a, b) => a || b],
+  ["==", (a, b) => a == b],
+  ["<=", (a, b) => a <= b],
+  [">=", (a, b) => a >= b],
+  ["<", (a, b) => a < b],
+  [">", (a, b) => a > b],
+]);
+
+export function evalExpr(expr: Expression, environment: Environment): any {
+  if (expr.kind === "literal") {
+    return expr.value;
+  }
+  else if (expr.kind === "ref") {
+    const found = environment.get(expr.variable);
+    if (found === undefined) {
+      throw new Error(`variable '${expr.variable}' does not exist in environment`);
+    }
+    return found;
+  }
+  else if (expr.kind === "unaryExpr") {
+    const arg = evalExpr(expr.expr, environment);
+    return UNARY_OPERATOR_MAP.get(expr.operator)!(arg);
+  }
+  else if (expr.kind === "binaryExpr") {
+    const lhs = evalExpr(expr.lhs, environment);
+    const rhs = evalExpr(expr.rhs, environment);
+    return BINARY_OPERATOR_MAP.get(expr.operator)!(lhs, rhs);
+  }
+  throw new Error("should never reach here");
+}

src/VisualEditor/ast.ts

@@ -43,21 +43,25 @@ export type Statechart = {
   uid2State: Map<string, ConcreteState>;
 }
 
+const emptyRoot: OrState = {
+  uid: "root",
+  kind: "or",
+  depth: 0,
+  initial: [],
+  children:[],
+  comments: [],
+  entryActions: [],
+  exitActions: [],
+};
+
 export const emptyStatechart: Statechart = {
-  root: {
+  root: emptyRoot,
-    uid: "root",
-    kind: "or",
-    initial: [],
-    children:[],
-    comments: [],
-    entryActions: [],
-    exitActions: [],
-  },
   transitions: new Map(),
   variables: new Set(),
   inputEvents: new Set(),
   internalEvents: new Set(),
   outputEvents: new Set(),
+  uid2State: new Map([["root", emptyRoot]]),
 };
 
 // reflexive, transitive relation
@@ -72,10 +76,19 @@ export function isAncestorOf({ancestor, descendant}: {ancestor: ConcreteState, d
   return pathToParent && [...pathToParent, descendant];
 }
 
+export function isOverlapping(a: ConcreteState, b: ConcreteState): boolean {
+  if (a.depth < b.depth) {
+    return Boolean(isAncestorOf({ancestor: a, descendant: b}));
+  }
+  else {
+    return Boolean(isAncestorOf({ancestor: b, descendant: a}));
+  }
+}
+
 // the arena of a transition is the lowest common ancestor state that is an OR-state
 // see "Deconstructing the Semantics of Big-Step Modelling Languages" by Shahram Esmaeilsabzali, 2009
 export function computeArena({src, tgt}: {src: ConcreteState, tgt: ConcreteState}): {
-  arena: ConcreteState,
+  arena: OrState,
   srcPath: ConcreteState[],
   tgtPath: ConcreteState[],
 } {
@@ -95,5 +108,24 @@ export function computeArena({src, tgt}: {src: ConcreteState, tgt: ConcreteState
     const {arena, srcPath, tgtPath} = computeArena({src: tgt, tgt: src});
     return {arena, srcPath: tgtPath, tgtPath: srcPath};
   }
-  throw new Error("should never reach here");
 }
+
+export function getDescendants(state: ConcreteState): Set<string> {
+  const result = new Set([state.uid]);
+  for (const child of state.children) {
+    for (const descendant of getDescendants(child)) {
+      // will include child itself:
+      result.add(descendant);
+    }
+  }
+  return result;
+}
+
+// the 'description' of a state is a human-readable string that (hopefully) identifies the state.
+// if the state contains a comment, we take the 'first' (= visually topmost) comment
+// otherwise we fall back to the state's UID.
+export function stateDescription(state: ConcreteState) {
+  const description = state.comments.length > 0 ? state.comments[0][1] : state.uid;
+  return description;
+}
+

src/VisualEditor/interpreter.ts

@@ -1,16 +1,17 @@
-import { computeArena, ConcreteState, isAncestorOf, Statechart, Transition } from "./ast";
+import { act } from "react";
-import { Action, Expression } from "./label_ast";
+import { evalExpr } from "./actionlang_interpreter";
+import { computeArena, ConcreteState, getDescendants, isAncestorOf, isOverlapping, OrState, Statechart, stateDescription, Transition } from "./ast";
+import { Action } from "./label_ast";
 import { Environment, RaisedEvents, Mode, RT_Statechart, initialRaised } from "./runtime_types";
 
 export function initialize(ast: Statechart): RT_Statechart {
-  const {mode, environment, ...raised} = enterDefault(ast.root, {
+  const {enteredStates, environment, ...raised} = enterDefault(ast.root, {
     environment: new Map(),
     ...initialRaised,
   });
   return {
-    mode,
+    mode: enteredStates,
     environment,
-    inputEvents: [],
     ...raised,
   };
 }
@@ -19,7 +20,7 @@ type ActionScope = {
   environment: Environment,
 } & RaisedEvents;
 
-type EnteredScope = { mode: Mode } & ActionScope;
+type EnteredScope = { enteredStates: Mode } & ActionScope;
 
 export function enterDefault(state: ConcreteState, rt: ActionScope): EnteredScope {
   let actionScope = rt;
@@ -30,25 +31,29 @@ export function enterDefault(state: ConcreteState, rt: ActionScope): EnteredScop
   }
 
   // enter children...
-  const mode: {[uid:string]: Mode} = {};
+  let enteredStates = new Set([state.uid]);
   if (state.kind === "and") {
     // enter every child
     for (const child of state.children) {
-      let childMode;
+      let enteredChildren;
-      ({mode: childMode, ...actionScope} = enterDefault(child, actionScope));
+      ({enteredStates: enteredChildren, ...actionScope} = enterDefault(child, actionScope));
-      mode[child.uid] = childMode;
+      enteredStates = enteredStates.union(enteredChildren);
     }
   }
   else if (state.kind === "or") {
     // same as AND-state, but we only enter the initial state(s)
-    for (const [_, child] of state.initial) {
+    if (state.initial.length > 0) {
-      let childMode;
+      if (state.initial.length > 1) {
-      ({mode: childMode, ...actionScope} = enterDefault(child, actionScope));
+        console.warn(state.uid + ': multiple initial states, only entering one of them');
-      mode[child.uid] = childMode;
+      }
+      let enteredChildren;
+      ({enteredStates: enteredChildren, ...actionScope} = enterDefault(state.initial[0][1], actionScope));
+      enteredStates = enteredStates.union(enteredChildren);
     }
+    console.warn(state.uid + ': no initial state');
   }
 
-  return { mode, ...actionScope };
+  return {enteredStates, ...actionScope};
 }
 
 export function enterPath(path: ConcreteState[], rt: ActionScope): EnteredScope {
@@ -62,48 +67,47 @@ export function enterPath(path: ConcreteState[], rt: ActionScope): EnteredScope
   }
 
   // enter children...
-
+  let enteredStates = new Set([state.uid]);
-  const mode: {[uid:string]: Mode} = {};
   if (state.kind === "and") {
     // enter every child
     for (const child of state.children) {
-      let childMode;
+      let enteredChildren;
       if (rest.length > 0 && child.uid === rest[0].uid) {
-        ({mode: childMode, ...actionScope} = enterPath(rest, actionScope));
+        ({enteredStates: enteredChildren, ...actionScope} = enterPath(rest, actionScope));
       }
       else {
-        ({mode: childMode, ...actionScope} = enterDefault(child, actionScope));
+        ({enteredStates: enteredChildren, ...actionScope} = enterDefault(child, actionScope));
       }
-      mode[child.uid] = childMode;
+      enteredStates = enteredStates.union(enteredChildren);
     }
   }
   else if (state.kind === "or") {
     if (rest.length > 0) {
-      let childMode;
+      let enteredChildren;
-      ({mode: childMode, ...actionScope} = enterPath(rest, actionScope));
+      ({enteredStates: enteredChildren, ...actionScope} = enterPath(rest, actionScope));
-      mode[rest[0].uid] = childMode;
+      enteredStates = enteredStates.union(enteredChildren);
     }
     else {
       // same as AND-state, but we only enter the initial state(s)
       for (const [_, child] of state.initial) {
-        let childMode;
+        let enteredChildren;
-        ({mode: childMode, ...actionScope} = enterDefault(child, actionScope));
+        ({enteredStates: enteredChildren, ...actionScope} = enterDefault(child, actionScope));
-        mode[child.uid] = childMode;
+        enteredStates = enteredStates.union(enteredChildren);
       }
     }
   }
 
-  return { mode, ...actionScope };
+  return { enteredStates, ...actionScope };
 }
 
+// exit the given state and all its active descendants
 export function exitCurrent(state: ConcreteState, rt: EnteredScope): ActionScope {
-  let {mode, ...actionScope} = rt;
+  let {enteredStates, ...actionScope} = rt;
 
   // exit all active children...
-  for (const [childUid, childMode] of Object.entries(mode)) {
+  for (const child of state.children) {
-    const child = state.children.find(child => child.uid === childUid);
+    if (enteredStates.has(child.uid)) {
-    if (child) {
+      actionScope = exitCurrent(child,  {enteredStates, ...actionScope});
-      (actionScope = exitCurrent(child, {mode: childMode, ...actionScope}));
     }
   }
 
@@ -115,6 +119,27 @@ export function exitCurrent(state: ConcreteState, rt: EnteredScope): ActionScope
   return actionScope;
 }
 
+export function exitPath(path: ConcreteState[], rt: EnteredScope): ActionScope {
+  let {enteredStates, ...actionScope} = rt;
+
+  const toExit = enteredStates.difference(new Set(path));
+
+  const [state, ...rest] = path;
+  
+  // exit state and all its children, *except* states along the rest of the path
+  actionScope = exitCurrent(state,  {enteredStates: toExit, ...actionScope});
+  if (rest.length > 0) {
+    actionScope = exitPath(rest, {enteredStates, ...actionScope});
+  }
+
+  // execute exit actions
+  for (const action of state.exitActions) {
+    (actionScope = execAction(action, actionScope));
+  }
+
+  return actionScope;
+}
+
 export function execAction(action: Action, rt: ActionScope): ActionScope {
   if (action.kind === "assignment") {
     const rhs = evalExpr(action.rhs, rt.environment);
@@ -144,117 +169,73 @@ export function execAction(action: Action, rt: ActionScope): ActionScope {
   throw new Error("should never reach here");
 }
 
-
+export function handleEvent(event: string, statechart: Statechart, activeParent: ConcreteState, {environment, mode, ...raised}: RT_Statechart): RT_Statechart {
-const UNARY_OPERATOR_MAP: Map<string, (x:any)=>any> = new Map([
+  const arenasFired = new Set<OrState>();
-  ["!", x => !x],
+  for (const state of activeParent.children) {
-  ["-", x => -x as any],
+    if (mode.has(state.uid)) {
-]);
+      const outgoing = statechart.transitions.get(state.uid) || [];
-
+      const triggered = outgoing.filter(transition => transition.label[0].trigger.kind === "event" && transition.label[0].trigger.event === event);
-const BINARY_OPERATOR_MAP: Map<string, (a:any,b:any)=>any> = new Map([
+      const enabled = triggered.filter(transition =>
-  ["+", (a,b) => a+b],
+        evalExpr(transition.label[0].guard, environment)
-  ["-", (a,b) => a-b],
+      );
-  ["*", (a,b) => a*b],
+      if (enabled.length > 0) {
-  ["/", (a,b) => a/b],
+        if (enabled.length > 1) {
-  ["&&", (a,b) => a&&b],
+          console.warn('nondeterminism!!!!');
-  ["||", (a,b) => a||b],
+        }
-  ["==", (a,b) => a==b],
+        const t = enabled[0];
-  ["<=", (a,b) => a<=b],
+        console.log('enabled:', transitionDescription(t));
-  [">=", (a,b) => a>=b],
+        const {arena, srcPath, tgtPath} = computeArena(t);
-  ["<", (a,b) => a<b],
+        let overlapping = false;
-  [">", (a,b) => a>b],
+        for (const alreadyFired of arenasFired) {
-]);
+          if (isOverlapping(arena, alreadyFired)) {
-
+            overlapping = true;
-export function evalExpr(expr: Expression, environment: Environment): any {
+          }
-  if (expr.kind === "literal") {
+        }
-    return expr.value;
+        if (!overlapping) {
-  }
+          console.log('^ firing');
-  else if (expr.kind === "ref") {
+          ({mode, environment, ...raised} = fireTransition(t, arena, srcPath, tgtPath, {mode, environment, ...raised}));
-    const found = environment.get(expr.variable);
+          arenasFired.add(arena);
-    if (found === undefined) {
+        }
-      throw new Error(`variable '${expr.variable}' does not exist in environment`)
+        else {
-    }
+          console.log('skip (overlapping arenas)');
-    return found;
+        }
-  }
+      }
-  else if (expr.kind === "unaryExpr") {
+      else {
-    const arg = evalExpr(expr.expr, environment);
+        // no enabled outgoing transitions, try the children:
-    return UNARY_OPERATOR_MAP.get(expr.operator)!(arg);
+        ({environment, mode, ...raised} = handleEvent(event, statechart, state, {environment, mode, ...raised}));
-  }
+      }
-  else if (expr.kind === "binaryExpr") {
-    const lhs = evalExpr(expr.lhs, environment);
-    const rhs = evalExpr(expr.rhs, environment);
-    return BINARY_OPERATOR_MAP.get(expr.operator)!(lhs,rhs);
-  }
-  throw new Error("should never reach here");
-}
-
-export function getActiveStates(mode: Mode): Set<string> {
-  return new Set([].concat(
-    ...Object.entries(mode).map(([childUid, childMode]) =>
-      [childUid, ...getActiveStates(childMode)])
-  ));
-}
-
-export function raiseEvent(event: string, statechart: Statechart, sourceState: ConcreteState, rt: RT_Statechart): RT_Statechart[] {
-  const activeStates = sourceState.children.filter(child => rt.mode.hasOwnProperty(child.uid))
-  for (const state of activeStates) {
-    const outgoing = statechart.transitions.get(state.uid) || [];
-    const enabled = outgoing.filter(transition => transition.label[0].trigger.kind === "event" && transition.label[0].trigger.event === event);
-    const enabledGuard = enabled.filter(transition =>
-      evalExpr(transition.label[0].guard, rt.environment)
-    );
-    if (enabledGuard.length > 0) {
-      const newRts = enabledGuard.map(t => fireTransition(t, statechart, rt));
-      return newRts;
-    }
-    else {
-      // no enabled outgoing transitions, try the children:
-      return raiseEvent(event, statechart, state, rt);
     }
   }
-  return [];
+  return {environment, mode, ...raised};
 }
 
-function setModeDeep(oldMode: Mode, pathToState: ConcreteState[], newMode: Mode): Mode {
+function transitionDescription(t: Transition) {
-  if (pathToState.length === 0) {
+  return stateDescription(t.src) + ' ➔ ' + stateDescription(t.tgt);
-    return newMode;
-  }
-  const [next, ...rest] = pathToState;
-  return {
-    ...oldMode,
-    [next.uid]: setModeDeep(oldMode[next.uid], rest, newMode),
-  }
 }
 
-function unsetModeDeep(oldMode: Mode, pathToState: ConcreteState[]): Mode {
+export function fireTransition(t: Transition, arena: OrState, srcPath: ConcreteState[], tgtPath: ConcreteState[], {mode, environment, ...raised}: RT_Statechart): {mode: Mode, environment: Environment} & RaisedEvents {
-  if (pathToState.length === 0) {
-    return {};
-  }
-  if (pathToState.length === 1) {
-    const keyToDelete = pathToState[0].uid;
-    const newMode = {...oldMode}; // shallow copy
-    delete newMode[keyToDelete];
-    return newMode;
-  }
-  const [next, ...rest] = pathToState;
-  return {
-    ...oldMode,
-    [next.uid]: unsetModeDeep(oldMode[next.uid], rest),
-  }
-}
 
-export function fireTransition(t: Transition, statechart: Statechart, rt: RT_Statechart): RT_Statechart {
+  console.log('fire ', transitionDescription(t), {arena, srcPath, tgtPath});
-  const {arena, srcPath, tgtPath} = computeArena(t);
+
-  const pathToArena = isAncestorOf({ancestor: statechart.root, descendant: arena}) as ConcreteState[];
+  // exit src
-  console.log('fire ', t.src.comments[0][1], '->', t.tgt.comments[0][1], {srcPath, tgtPath});
+  ({environment, ...raised} = exitPath(srcPath.slice(1), {environment, enteredStates: mode, ...raised}));
-  let {environment, ...raised} = exitCurrent(srcPath[1], rt);
+  const toExit = getDescendants(arena);
-  const exitedMode = unsetModeDeep(rt.mode, [...pathToArena.slice(1), ...srcPath.slice(1)]);
+  toExit.delete(arena.uid); // do not exit the arena itself
+  const exitedMode = mode.difference(toExit);
+
+  console.log('exitedMode', exitedMode);
+
+  // exec transition actions
   for (const action of t.label[0].actions) {
     ({environment, ...raised} = execAction(action, {environment, ...raised}));
   }
-  let deepMode;
+
-  ({mode: deepMode, environment, ...raised} = enterPath(tgtPath.slice(1), {environment, ...raised}));
+  // enter tgt
-  // console.log('entered path:', tgtPath.slice(1), {deepMode});
+  let enteredStates;
-  const enteredMode = setModeDeep(exitedMode, [...pathToArena.slice(1), ...tgtPath.slice(1)], deepMode);
+  ({enteredStates, environment, ...raised} = enterPath(tgtPath.slice(1), {environment, ...raised}));
-  // console.log('pathToArena:', pathToArena, 'newMode:', enteredMode);
+  const enteredMode = exitedMode.union(enteredStates);
-  return {mode: enteredMode, environment, inputEvents: rt.inputEvents, ...raised};
+
+  console.log('enteredMode', enteredMode);
+
+  return {mode: enteredMode, environment, ...raised};
 }

src/VisualEditor/parser.ts

@@ -225,6 +225,7 @@ export function parseStatechart(state: VisualEditorState): [Statechart, [string,
     inputEvents,
     internalEvents,
     outputEvents,
+    uid2State,
   }, errorShapes];
 }
 

src/VisualEditor/runtime_types.ts

@@ -2,7 +2,11 @@
 // for OR-states, only the modal configuration of the current state is kept
 // for AND-states, the modal configuration of every child is kept
 // for basic states (= empty AND-states), the modal configuration is just an empty object
-export type Mode = {[uid:string]: Mode};
+// export type Mode = {[uid:string]: Mode};
+
+
+export type Mode = Set<string>; // set of active states
+
 
 export type Environment = ReadonlyMap<string, any>; // variable name -> value
 
@@ -10,8 +14,6 @@ export type RT_Statechart = {
   mode: Mode;
   environment: Environment;
   // history: // TODO
-
-  inputEvents: string[];
 } & RaisedEvents;
 
 export type RaisedEvents = {