Hello Zhang,
one wonders, what the purpose of this effort is: Modelling a paper process in BPMN - for redocumentation?
Rules of thumb:
- A pool is equivalent to a process. "Patient sign-in"
- You have 3 roles here: Receptionist, nurse and secretary. You might use 3 lanes in the Pool, but that is not obligatory.
- Use a Sub-Process for everything a role does in one go until responsibility passes to another role. If more detail is required - as appears to be the case here - model that inside the sub-process.
- Use Active voice: "Secretary is given..." is passive voice and it's unclear who is acting. Next point: Eliminate the actors from the tasks e.g. "register patient". Organizational aspects are out-of-scope of BPMN 2.0. It is concerned with the acitivities only. (See chapter 7.2 of the spec)
- Data flows are not modelled in BPMN. Inter-process communication is realized as the exchange of messages between Pools, but that is not the case here. So eliminate everything concerned with the passing of information