The sequencer control the flow of request and response sequence items between sequences and the driver.
Sequencer and driver uses TLM Interface to communicate transactions.
uvm_sequecner and uvm_driver base classes has seq_item_export and seq_item_port defined respectively. User need to connect them using TLM connect method.
Sequencer can be written by extending the uvm_sequencer parameterized with seq_item type.
Writing Scoreboard :
class mem_sequencer extends uvm_sequencer#(mem_seq_item); `uvm_sequencer_utils(mem_sequencer) function new (string name, uvm_component parent); super.new(name, parent); endfunction : new endclass : mem_sequencer