public class InfoPlusEvent
    {
        // *who*, sometimes can also be found in Step.AssignUser
        public InfoPlusUser User { get; set; }
        // *who* actually made this move. in other words, the *Entruster*
        public InfoPlusUser ActualUser { get; set; }
        // *when*, unix timestamp
        public long When { get; set; }

        // *what* data it is,
        // especially, ON_FIELD_CHANGING will assign value here to indicate: 
        //      which field changed, changed to what.
        public IDictionary<string, object> FormData { get; set; }

        // *where* the data located.
        // public string Path { get; set; }
        // Field Events
        public string Field { get; set; }
        public string FieldPath { get; set; }

        // suggestion data, only valid for FIELD_CHANGING
        public CodeSuggestion Suggestion { get; set; }

        // *how* could the data be?
        public IList<FormField> Fields { get; set; }

        // which step/instance/definition/form/application
        public FormStep Step { get; set; }

        // which action & users are chosen
        public string ActionCode { get; set; }
        public string ActionName { get; set; }
        public IList<FormStep> NextSteps { get; set; }
        public FormStep EndStep { get; set; }

        // result, only available for DONE/STARTED...
        public ResponseEntity<object> Result { get; set; }

        /// <summary>
        /// Whether release/beta instance 
        /// </summary>
        public bool Release { get; set; }

        /// <summary>
        /// AccessTokens for resources that: defined in workflow resources, granted by user, fetched by engine GUI
        /// only available in Events that after user interact
        /// </summary>
        public IDictionary<string, string> Tokens { get; set; }
    }

    public class InfoPlusResponse
    {
        /// <summary>
        /// cancel the current doing if Cancel == True
        /// </summary>
        public bool Cancel { get; set; }

        /// <summary>
        /// when you cancel the event, give the user a prompt.
        /// </summary>
        public string Prompt { get; set; }

        /// <summary>
        /// for Expiration.
        /// 0: do nothing
        /// -1: kill
        /// positive: seconds to extend.
        /// </summary>
        public long Then { get; set; }

        /// <summary>
        /// Then, after Expiration, submit an Action
        /// </summary>
        public long ThenAction { get; set; }

        /// <summary>
        /// Detail will contain exception infomation
        /// </summary>
        public string Detail { get; set; }

        /// <summary>
        /// Response form data, when: 
        ///     WorkflowStarting as Initialization data
        ///     FieldChanging as auto fills.
        /// </summary>
        public IDictionary<string, object> FormData { get; set; }

        /// <summary>
        /// Codes. Maybe a list of CodeList, which used when:
        /// 1.ON_FIELD_SUGGESTING return only one CodeList suggested,
        /// 2.ON_STEP_RENDERING/ED, return CodeLists should be initialized.
        /// 3.ON_FIELD_CHANGING, as above.
        /// </summary>
        public IList<CodeList> Codes { get; set; }

    }