Question: what are the different layers of layered architecture in sv?
Answer: signal layer: This layer connects the TestBench to the RTL design. ... 
command layer: This layer contains lower-level driver and monitor components, as well as the assertions. ... 
functional layer: ... 
scenario layer: ... 
test layer: ... 
VMM Standard Library.
VMM Register Abstraction Layer (RAL)
VMM Hardware Abstraction Layer (HAL)