Do joists need to be attached to the beam they're resting on?
The Code (See ICC Table 2304.9.1) requires joists toenailed into beams by: 


3 - 8d common nails, or
3 - 10d box nails, or
3 - 3” x 0.131” nails, or
3 - 14 ga. Staples with 7/16” crown.