I have an ecommerce where users can ask questions on the product and the users who bought it can answer the questions and also vote on the questions like amazon , which means that the system will technically send all answers and votes to the user and the user will send answers and votes also.
So the same data is exchanged between the system and the customer, how can I represent it in a context diagram? I added an arrow head in both ends , is this correct?
Dataflow diagrams frequently use unidirectional flows between processes or between processes and entities, but bidirectional flows with an arrow on both sides are a common practice that is perfectly valid.
The authors who popularised the two mainstream variants of DFD modelling Gane & Sarson or Yourdon & DeMarco), both refer to it in their foundational books: Yourdon uses it in several examples, Gane and Sarson even recommend it for keeping diagrams simple.