--- a/Implab/IPromise.cs	Mon Feb 16 17:48:39 2015 +0300
+++ b/Implab/IPromise.cs	Tue Feb 17 18:16:26 2015 +0300
@@ -22,6 +22,11 @@
         bool IsCancelled { get; }
 
         /// <summary>
+        /// Исключение возникшее в результате выполнения обещания, либо причина отмены.
+        /// </summary>
+        Exception Error { get; }
+
+        /// <summary>
         /// Creates a new promise dependend on the current one and resolved on
         /// executing the specified handlers.
         /// </summary>
@@ -43,19 +48,21 @@
         /// exception then the dependant promise will be resolved successfully, otherwise the exception
         /// raised by the handler will be transmitted to the dependent promise. If the handler wants
         /// to passthrough the original exception it needs to wrap the exception with
-        /// the <see cref="PromiseTransientException"/>.
+        /// the <see cref="PromiseTransientException"/>. The handler may raise <see cref="OperationCanceledException"/>
+        /// to cancel the dependant promise, the innner exception specifies the reason why the promise
+        /// is canceled.
         /// </para>
         /// <para>
         /// If the cancelation handler is specified and the current promise is cancelled then the dependent
-        /// promise will be resolved after the handler is executed. If the cancelation hendler raises the
+        /// promise will be resolved after the handler is executed. If the cancelation handler raises the
         /// exception it will be passed to the dependent promise.
         /// </para>
         /// </remarks>
-        IPromise Then(Action success, Action<Exception> error, Action cancel);
+        IPromise Then(Action success, Action<Exception> error, Action<Exception> cancel);
         IPromise Then(Action success, Action<Exception> error);
         IPromise Then(Action success);
 
-        IPromise Chain(Func<IPromise> chained, Func<Exception, IPromise> error, Func<IPromise> cancel);
+        IPromise Chain(Func<IPromise> chained, Func<Exception, IPromise> error, Func<Exception, IPromise> cancel);
         IPromise Chain(Func<IPromise> chained, Func<Exception, IPromise> error);
         IPromise Chain(Func<IPromise> chained);
 
@@ -66,7 +73,7 @@
         /// <param name="error">The handler is called if an error while completing the promise occurred.</param>
         /// <param name="cancel">The handler is called in case of promise cancellation.</param>
         /// <returns>The current promise.</returns>
-        IPromise On(Action success, Action<Exception> error, Action cancel);
+        IPromise On(Action success, Action<Exception> error, Action<Exception> cancel);
         IPromise On(Action success, Action<Exception> error);
         IPromise On(Action success);
 
@@ -80,42 +87,6 @@
         IPromise On(Action handler, PromiseEventType events);
 
         /// <summary>
-        /// Adds the specified error handler to the current promise
-        /// and creates the new dependant promise.
-        /// </summary>
-        /// <param name="error">
-        /// The error handler. If the error handler returns without
-        /// an error the dependant promise will be successfully resolved.
-        /// </param>
-        /// <returns>
-        /// The new dependant promise which will be resolved after the error
-        /// handler is executed.
-        /// </returns>
-        /// <remarks>
-        /// The successfull result of the current promise will be ignored.
-        /// </remarks>
-        IPromise Error(Action<Exception> error);
-
-        /// <summary>
-        /// Adds the specified cncellation handler to the current promise
-        /// and creates the new dependant promise.
-        /// </summary>
-        /// <returns>
-        /// The new dependant promise which will be resolved after the cancellation
-        /// handler is executed.
-        /// </returns>
-        /// <param name="handler">
-        /// The cancellation handler.
-        /// </param>
-        /// <remarks>
-        /// If the cancellation handler is executed without an error the dependent
-        /// promise will be successfully resolved, otherwise the raised exception
-        /// will be passed to the dependant promise. The successful result of the
-        /// current promise will be ignored.
-        /// </remarks>
-        IPromise Cancelled(Action handler);
-
-        /// <summary>
         /// Преобразует результат обещания к заданному типу и возвращает новое обещание.
         /// </summary>
         IPromise<T> Cast<T>();