elines ▁are ▁established ▁after ▁four ▁of ▁the ▁five ▁phases ▁of ▁the ▁SD LC ▁and ▁are ▁critical ▁to ▁the ▁iter ative ▁nature ▁of ▁the ▁model ▁. ▁Each ▁bas eline ▁is ▁considered ▁as ▁a ▁mil estone ▁in ▁the ▁SD LC . ▁▁ ▁functional ▁bas eline : ▁established ▁after ▁the ▁concept ual ▁design ▁phase . ▁ ▁allocated ▁bas eline : ▁established ▁after ▁the ▁pre lim inary ▁design ▁phase . ▁ ▁product ▁bas eline : ▁established ▁after ▁the ▁detail ▁design ▁and ▁development ▁phase . ▁ ▁updated ▁product ▁bas eline : ▁established ▁after ▁the ▁production ▁construction ▁phase . ▁ ▁Com plement ary ▁method ologies ▁▁ ▁Com plement ary ▁software ▁development ▁methods ▁to ▁systems ▁development ▁life ▁cycle ▁are : ▁▁ ▁Software ▁pro tot yp ing ▁ ▁J oint ▁applications ▁development ▁( J AD ) ▁ ▁Rap id ▁application ▁development ▁( R AD ) ▁ ▁Ext reme ▁programming ▁( X P ); ▁ ▁Open - source ▁development ▁ ▁End - user ▁development ▁ ▁Object - orient ed ▁programming ▁ ▁Str ength s ▁and ▁weak ness es ▁▁ ▁F ew ▁people ▁in ▁the ▁modern ▁computing ▁world ▁would ▁use ▁a ▁strict ▁water fall ▁model ▁for ▁their ▁SD LC ▁as ▁many ▁modern ▁method ologies ▁have ▁su pers eded ▁this ▁thinking . ▁Some ▁will ▁argue ▁that ▁the ▁SD LC ▁no ▁longer ▁applies ▁to ▁models ▁like ▁Ag ile ▁computing , ▁but ▁it ▁is ▁still ▁a ▁term ▁widely ▁in ▁use ▁in ▁technology ▁circles . ▁The ▁SD LC ▁practice ▁has ▁advantages ▁in ▁traditional ▁models ▁of ▁systems ▁development ▁that ▁l ends ▁itself ▁more ▁to ▁a ▁struct ured ▁environment