In reply to DamianS:
I think the UVM macros confuses the two concepts of sequences and sequence_items. (probably leftover from OVM)
A sequence is a handle to a procedural body of code (hence the body() method). See the functon pointer OOP design pattern). There is no arbitration required for sequences.
A sequence_item is a transaction of data that you want dest to a driver. Arbitration gets manages by a sequencer. You can start sequences from components like the test, and from other sequences.