▁summary ▁fashion . ▁In ▁addition , ▁the ▁upper ▁section ▁should ▁provide ▁an ▁over view ▁of ▁the ▁full ▁scope ▁and ▁tim eline ▁of ▁the ▁project ▁and ▁will ▁be ▁part ▁of ▁the ▁initial ▁project ▁description ▁effort ▁leading ▁to ▁project ▁appro val . ▁The ▁middle ▁section ▁of ▁the ▁W BS ▁is ▁based ▁on ▁the ▁seven ▁systems ▁development ▁life ▁cycle ▁phases ▁as ▁a ▁guide ▁for ▁W BS ▁task ▁development . ▁The ▁W BS ▁elements ▁should ▁consist ▁of ▁mil est ones ▁and ▁" tasks " ▁as ▁opposed ▁to ▁" activ ities " ▁and ▁have ▁a ▁definit ive ▁period ▁( us ually ▁two ▁weeks ▁or ▁more ). ▁Each ▁task ▁must ▁have ▁a ▁meas urable ▁output ▁( e . x . ▁document , ▁decision , ▁or ▁analysis ). ▁A ▁W BS ▁task ▁may ▁rely ▁on ▁one ▁or ▁more ▁activities ▁( e . g . ▁software ▁engineering , ▁systems ▁engineering ) ▁and ▁may ▁require ▁close ▁coord ination ▁with ▁other ▁tasks , ▁either ▁internal ▁or ▁external ▁to ▁the ▁project . ▁Any ▁part ▁of ▁the ▁project ▁need ing ▁support ▁from ▁contract ors ▁should ▁have ▁a ▁statement ▁of ▁work ▁( SO W ) ▁written ▁to ▁include ▁the ▁appropriate ▁tasks ▁from ▁the ▁SD LC ▁phases . ▁The ▁development ▁of ▁a ▁SO W ▁does ▁not ▁occur ▁during ▁a ▁specific ▁phase ▁of ▁SD LC ▁but ▁is ▁developed ▁to ▁include ▁the ▁work ▁from ▁the ▁SD LC ▁process ▁that ▁may ▁be ▁conducted ▁by ▁external ▁resources ▁such ▁as ▁contract ors . ▁ ▁Bas elines ▁▁ ▁Bas elines ▁are ▁an ▁important ▁part ▁of ▁the ▁systems ▁development ▁life ▁cycle . ▁These ▁bas