Update description of launch-wait for streaming case

hpvm/docs/hpvm-specification.md

@@ -48,13 +48,17 @@ Stop tracking specified memory object and remove it from memory tracker.
 - **Request Memory**:
 If the specified memory object is not present in host memory, copy it to host memory.
 - **Launch**:
-The host code initiates execution of specified DFG, either streaming or non streaming, and provides initial data. All data for one graph execution must be provided.
-- **Wait**:
-The host code blocks for completion of specified DFG.
+The host code initiates execution of specified DFG, either streaming or non streaming.
+    - Non streaming DFG: The host provides all data items required for execution of the DFG at the time of the launch.
+    - Streaming DFG: No data is provided by the launch operation. Streaming execution is sustained by push and pop operations, described below.
 - **Push**:
-Push a set of data required for one graph execution to the specified DFG. The DFG must have been launched using a streaming launch operation. This is a blocking operation.
+Push a set of data items required for one graph execution to the specified DFG. The DFG must have been launched using a streaming launch operation. This is a blocking operation.
 - **Pop**:
 Read data produced from one execution of the specified DFG. The DFG must have been launched using a streaming launch operation. This is a blocking operation.
+- **Wait**:
+The host code blocks for completion of specified DFG.
+    - For a non-streaming DFG, the data produced by the DFG are ready to be read by the host.
+    - For a streaming DFG, no more data may be provided for processing by the DFG.
 
 # HPVM Implementation