diff --git a/doc/design/model_format.md b/doc/design/model_format.md
index 754bb398e0b996fdf88250a7e0d124bd7bb7e235..a1c086775acbee6d05ebf69d7de9c7c3ac2cd36e 100644
--- a/doc/design/model_format.md
+++ b/doc/design/model_format.md
@@ -34,5 +34,5 @@ The table below shows a tensor's byte view in detail. Note that all the signed v
 ## Summary
 
 - We introduce a model format.
-- The `ProgramDesc` describe the model **topology**. 
+- The model represented by its forward-pass computation procedure is saved in a **ProgramDesc** protobuf message.
 - A bunch of specified format binary tensors describe the **parameters**.