In reply to rajan passionate:
But ben, how to use non-clocked delays for checking the sequences? (Delays less than one clock cycle).
SVA is event-based with variables samples in the Preponed region of the event.
Events are usually clocking event, but could be user-defined events (declared with the event type).
Assertions are really intended to verify and cover properties based on the relationships of variables (e.g, req |=> ack)
For delays, you could use supporting logic yo create events.
Write multiple small assertions instead of 1 compex one.
Ben