diff --git a/timeline-chart/src/time-graph-model.ts b/timeline-chart/src/time-graph-model.ts
index 1bdbff2..e1c0aa3 100644
--- a/timeline-chart/src/time-graph-model.ts
+++ b/timeline-chart/src/time-graph-model.ts
@@ -9,6 +9,7 @@ export namespace TimelineChart {
         totalLength: number
         rows: TimeGraphRowModel[]
         arrows: TimeGraphArrow[]
+        readonly data?: { [key: string]: any }
     }
 
     export interface TimeGraphRowModel {