Chng 6 : K thut c lngD on l kh khn ; c bit l d on tng lai.Din gii ca mt trch dn khc bi Samuel Goldwyn v Yogi Berra6.1 : Gii thiu v k thut c lng.Mc ch ca c lng l xc nh mt mt tp hp cc thng s cung cp mc tin tng cao, bn s c th cung cp mt sn phm c chp nhn trong gii hn ca nhng rng buc ca d n.Cc thng s v cc rng buc xem xt : c trng sn phm. Thuc tnh cht lng. Cng sc Cc ti nguyn khc. K hoch. Ngn sch. Cng ngh.Mt s thng s c quy nh nh cc rng buc v mt s khc c c lng. V d, bn c th a ra mt tp cc yu cu v mt cng ngh c bn (Cc thng s rng buc c th : c trng v thuc tnh cht lng, nn tng phn cng v h iu hnh ), v cc yu cu c lng bao nhiu thi gian, cng sc, cc ti nguyn khc v ngn sch cn(c lng cc thng s). Bn cng nn ch ra mc tin tng ca bn trong c lng. Hoc, bn c th a ra mt k hoch, ngn sch, ti nguyn v yu cu c lng tp hp cc c trng v thuc tnh cht lng c th pht trin trong cc rng buc . Cc s kt hp khc c th c. Kinh nghim cho thy vic pht trin thc t mt s n phn mm l mt li nguy c ca mt qu trnh. Sau khi thc hin, thuc tnh d n nh l n lc thc t, tin , ti nguyn, chi ph, c trng ca sn phm, v thuc tnh cht lng thng khc nhiu so vi thng s c lng. C vi nguyn nhn ca tnh hung ri ro: Nhng c tnh ban u ca cng sc v tin c th m h v da trn cc yu cu thay i. Nhng c tnh ban u khng c cp nht t nhng kin thc t c v s hiu bit tng thm. Nhng c s c tnh c th khng khng ph hp vi d n c c tnh. Phng php v cng c s dng c tnh c th khng ph hp. S nhc nh ca cc chuyn gia t vn c th khng chnh xc v sai lch. Hon thnh sn phm c th l ln hoc phc tp hn gi nh khi lp d ton. Tin v ti nguyn c th b gim m khng iu chnh cc yu cu ca c trng sn phm v cht lng thuc tnh. Cc yu cu v c trng sn phm v cht lng thuc tnh c th tng m khng iu chnh tin v ti nguyn. S lng cc phn mm pht trin c h tr v trnh k nng ca chng c th khng nh gi nh khi lp d ton. Cc yu t bn ngoi nh s thay i bt ng phn cng v giao din phn mm hoc hon thnh cng vic mun ca mt nh thu ph c th tr hon d n hon thnh.Mc ch ca mc ny cung cp phng php, cng c v cng ngh c th gim xc sut lp d ton khng tt.6.2 Mc tiu ca chng ny :Mc tiu cn t c : Vai tr ca d ton trong m hnh quy trnh ca d n phm mm. Ba nguyn tc c bn ca c tnh. Phng php kch thc v o kch thc. Lm th no pht trin mt bin php kch thc. Mt s thc t, l thuyt c bn, k thut c lng, hi quy, m hnh thut ton. Kh nng ca cng c d ton. Th tc lp d ton Mt nh dng ti liu c tnh.Bn nhm tiu chun v hng dn qun l d n c trnh by trong vn bn; c th l CMMI- DEV v1.2 khun kh qu trnh, ISO/IEEE tiu chun 12207, IEEE tiu chun 1058 , v PMI kin thc lp d ton vi cc vn mc khc nhau.6.3 Nguyn tc c bn ca c tnh.Ba nguyn tc c bn c m t v bn lun trong mc ny. Nguyn tc c bn u tin vi d n phn mm c nu ra nh sau :Nguyn tc c bn 1 : c tnh mt d n l php chiu t kinh nghim qu kh n tng lai, iu chnh gii thch cho s khc bit gia qu kh v tng lai.Ba iu ny r rng t nguyn tc ny :1 . Bn phi c mt s kinh nghim qu kh c rt ra.(gi l c s d ton)2. Bn phi bit iu g v tng lai.(yu cu i vi h thng v sn phm bn phi pht trin)3. Bn phi c nhng iu chnh gii thch cho s khc bit gia qu kh v tng lai.Tt c cng ngh d ton d n phn mm kt hp cht ch, theo nhng cch khc nhau v mc kinh nghim qu kh, kin thc tng lai v s iu chnh cc yu t. Kinh nghim trong qu kh c th l dn n quy tc ngn tay ci. Cc phn sn xut phn mm trong t chc ca bn, cho loi hnh d n, thng l 500 dng code cho mi nhn vin mi thng(500DSLOC/sm). Nu bn phi c tnh tng lai sn phm s c 50 000 dng code (da vo kinh nghim qu kh) v nu tng lai d n c cho l tng t d n trong qu kh, n s yu cu mt c tnh 100 nhn vin mi thng.Trong trng hp khng c cc vn iu chnh, bn phi ln k hoch cho d n trong 10 thng s dng 10 nh pht trin phn mm. nu bn ngh sn phm c pht trin s nhiu phc tp hn sn phm c, bn c th tng s n lc c tnh ln 120 nhn vin mi thng v k hoch d n cho 12 thng s dng 10 nh pht trin. Ngc li, bn c th gim s n lc c tnh nu bn ngh sn phm s t phc tp hn sn phm c v bn ngh nh pht trin phn mm c c s quen thuc vi loi hnh pht trin sn phm tng t.D liu lch s da trn kinh nghim trong qu kh cng c th ch ra rng s lng khuyt tt tm thy c trc khi pht hnh sn phm thng l 10/1000 dng code v s lng c tm thy bi ngi dng trong 6 thng u tin hot ng l mi KDSLOC. Bn c th c tnh rng 500 khuyt tt nn c tm thy trc khi sn phm pht hnh(50x10) v 50 s bo co bi ngi dng trong qu trnh 6 thng hot ng u tin.Thit lp d ton, bn c th gi thit vi iu. V d, bn c th gi thit rng sn phm s phc tp tng t nh xy dng mt sn phm trc y. Do bn khng p dng mt s iu chnh phc tp. Bn c th gi thit rng ngi pht trin ca sn phm tng lai s tng t v kh nng vi nhng ngi trc v nng sut, quy tc ngn tay ci (500 DSLOC/SM); nu khng, bn s iu chnh mt yu t tng hoc gim c s c tnh trong gi thit lm th no kh nng sn xut ca ngi pht trin s khc vi kh nng trong qu kh.

Hnh 6.1 Qu trnh c lng.Hnh trn minh ha vai tr ca cc thuc tnh ca sn phm c ngi pht trin hoc sa i, nhng kh khn ca n, kinh nghim trong qu kh, gi nh, v iu chnh cc yu t. Hnh trn lin quan n cc m hnh lm vic cho cc d n phn mm.

6.2 M hnh lung cng vic qun l d n phn mmMt so snh cc hnh 6.1 v 6.2 cho thy rng thuc tnh sn phm c ngun gc t yu cu ca ngi dng. Kh khn ca d n bao gm rng buc t khch hng, ch th qun l v rng buc. Kinh nghim qu kh c tm tt bi yu t d liu hnh 6.2, nhng kinh nghim ny c th tm tt trong mt c s d liu ca d n khi hon thnh, trong u cc chuyn gia, trong quy tc ngn tay ci, cc ngnh trung bnh, hoc trong vn ha truyn thng. Yu t c iu chnh c p dng cho ti khon c yu cu hiu bit v lm th no chng khc nhau t kinh nghim qu kh, cng nh s khc bit v thng s d n nh trnh k nng, sn c v ngun lc, v hn ch v tin .Tm tt da trn cc yu t bn tin tng l ng hoc bn s tin tng l ng. Quy hoch li thng lin quan n ti lp d ton, thng da trn s thay i yu cu, ch dn mi v cc rng buc v nh cc yu cu bo co c vn . Tip tc vi v d trn : Thuc tnh ca sn phm trong tng lai vi gi nh kch thc c lng l 50000 DLOC. Kinh nghim qu kh gi nh nh quy tc ngn tay ci (500 DSLOC/SM) v pht hnh trc v pht hnh sau cc khim khuyt. Nu khng c s iu chnh yu t c thc hin, gi thit rng d n tng lai s tng t nh mi cch xy dng d n trong qu kh l c s c tnh. iu chnh cc yu t c thc hin ti tnh ton khc nhau gia d n c v d n mi.iu chnh cc yu t thuc tnh dng nh vi d n tng t to s khc bit v cng sc , tin , ngun lc , chi ph, c trng, thuc tnh cht lng hoc cc thuc tnh quan tm khc. iu chnh yu t tiu biu bao gm : Phc tp tng i ca sn phm, Cc k nng v kh nng ca cc nh pht trin S c bit v bin ng ca cc yu cu Hn ch qu mc v p lc tin .Mi yu t c th tt hn hoc xu i so vi d n tiu biu trong qu kh.iu chnh cc yu t quan trng trong vic c lng d n phn mm v khng c hai d n no ging nhau; mt khc, bn c th to bn copy mt s im tn ti ca phn mm v a n cho khch hng. Ni cch khc, mi d n phn mm kt hp cc kha cnh c o. L do bn lm d n phn mm l sn xut phn mm khng ging nh bit k ci ca ngi khc hoc t chc khc pht trin.Vn ny ca phn mm khc nhau t thc th vt l. Mt s lng ln cng sc l yu cu xy dng li ta nh, mt ci moto hoc mt my tnh. Khi kt thc, cc thc th vt l s tng t nhau, nhng khng ging bn gc. Mc ch ca sn xut ny l qu trnh sn xut nhiu bn sao sao cho cng ging hin vt cng tt, trong gii hn cng ngh v cn nhc kinh t, nhng kt qu l khng bao gi ging ht nhau. Mc tiu chnh ca d n phn mm ca bn phi to ra bn sao chp nhn c ng thi hn v trong ngn sch. Sau , bn c th d dng sn xut nhiu bn sao ging ht nhau vi phn mm bn mong mun, cc khuyt tt v tt c.Trong v d trn, bn c th ngh sn phm c xy dng s nhiu kh khn hn sn phm tiu biu trong qu kh, v vy bn c th iu chnh c lng ln 20% tnh ton tng phc tp. Bn c th ln lch d trong 10 thng vi mc trung bnh 12 nh pht trin phn mm. Nu tin l hn ch trong 9 thng, iu chnh tuyn tnh cc nhn vin khong 13 FTE ngi pht trin cn thit.

Nh trn s cho thy sau , s bi thng l khng ; hn 13.3 ngi pht trin phn mm s l cn thit b p cho vic nn tin v tng mc giao tip v phi hp cn thit khi c nhiu ngi thm vo.Tt c cc d tnh da trn gi nh v cc rng buc. Mt gi nh tuyn b c a ra n chn tht m khng xc minh, hoc c th xc minh, s tht c tuyn b. Trong v d trn, n c gi nh rng cc yu t nng sut trong t chc ca bn (500 DSLOC/SM) v cc khuyt im c tnh (10 /KDSLOC v 1/KDSLOC) thch hp cho d n ca bn. c tnh iu chnh tng 20% bi v gi thit rng phc tp tng ln s i hi s n lc nhiu d n trc . c lng c th c th iu chnh xung da trn gi nh rng bn c mt i k nng cao v pht trin phn mm, nhng ngi ny s b p cho s tng phc tp ca sn phm. Mt hn ch l mt iu kin ngoi p t phi c qua st. Trong v d trn, tin c th hn ch trong 6 thng. Hon thnh vi 120 nhn vin n lc trong 6 thng s i hi mt mc trung bnh ca nhn vin hn 20 nh pht trin phn mm(120/6 = 20) ; Hn 20 v mc tng thng tin lin lc v phi hp cn thit cho 20 FTEs 20 so vi 10 FTEs trn 12 thng lch trnh s gim nng sut c th ca mi nh pht trin phn mm. Ngoi lch trnh nn s c kh nagnw tng s lng cc khuyt tt trc pht hnh v sau pht hnh.Thm vo c th khng th nn 12 thng thnh 6 thng bi v mt s sn phm cng vic phai c hon thnh trc khi lm cng vic khc c bt u. Bn khng th pht trin phn mm cho n khi bit cc yu cu. Bn khng th tch hp hoc kim tra code cho n khi n c vit. Cc yu t hn ch l phn mm sn c cht lng phn mm vi ngi dng hoc chuyn giao phn cng cn c hoc phn mm c th ngn nga nn lch trnh. D liu lch s c th ch ra rng khng c d n trong t chc m thnh cng khi nn lch trnh d kin n 50%.c tnh c bn 2 : Tt c cc c tnh c da trn tp cc gi thit phi c thc hin v mt tp rng buc phi c tha mn.Ni mt cch khc, c tnh ca bn s khng c hiu lc nu bn khng p ng cc gi nh thc hin cho d ton; d n s khng p ng c cc mc tiu nu vi phm cc rng buc.Mt cch khc cho thy gi nh v cc rng buc m c tnh da trn gi nh v hn ch cc ri ro cho d n ca bn. Mt yu t ri ro l vn tim tng s tr thnh mt vn thc t, s to thnh kh khn cho vic t c kt qu kh quan cho d n. V d, Can c c tnh trn gi nh cc nh pht trin c chuyn mn cao to ra yu t ri ro s lm mt hiu lc c tnh nu cc nh pht trin phn mm khng c tay ngh cao. C gng hon thnh d n trong 6 thng s dng 20 ngi c th to ra cc vn v giao tip v phi hp s ngn chn hon thnh tin d n hoc c th dn n khng t yu cu sn phm.c tnh c bn 3 : d n phi ti lp c tnh nh k nh cc hiu bit thm v nh k vi cc thng s d n thay i.Nguyn tc ny l mt h qu ca nguyn tc 2. Khi tin hnh d n, s hiu bit v sn phm ca bn c pht trin, cc gi nh bn s thc hin, v cc tc ng kh khn s tr nn r rng. V d, sn phm c th nhiu hn hoc t phc tp hn bn gi nh; pht trin ca bn c th nhiu hn hoc t c tay ngh cao hoc t c ng c hn bn gi nh; nhng hn ch lch trnh c th c nhiu hn hoc t nghim trong hn bn tng. S hiu bit tt hn, tnh hp l ca cc gi thit ca bn, v tc ng ca cc sn phm v hn ch qu trnh ti lp c tnh v ti lp k hoch nh hnh 6.2.Nh mt lut, ti lp c tnh v lp k hoch nn xy ra trn c s hng thng cho cc d n di 12 thng v hng thng, hng qu cho cc d n trn 12 thng. Khong thi gian cn c xc nh bi s n nh ca cc yu cu, cc ngun lc, cng ngh v s pht trin qu trnh. D n phi c ti lp c lng theo nh k khi c s thay i bt ng xy ra, cc thng s d n nh : Mt s thay i ln trong yu cu Tht bi ca cng ngh mi Nn lch trnh Gim ngn sch theo k hoch Mt ngi ch cht.Lp li k hoch c th c yu cu, ty thuc vo ln ca nhng thay i bt ng.Nh ni trong vn bn, cch chp nhn vi cc thay i trong thng s d n gm: Ti thit lp phm vi yu cu M rng lch trnh Thm ngun lc S dng ngun lc tt Lm thm gi qu nhiu Gim cc hot ng kim tra v xc nhn k hoch Gim trong ti liu k hoch.Nu bn cam kt mt mc gi c nh v k hoach trong hp ng ng tin yu cu cng nhc. Bn phi c d tr trong cc tha thun, thun gi v lch trnh cha cc thay i nh s hiu bit tng ln( Cc d n lun ln hn v phc tp hn so vi gi nh). D tr c th dao ng t 10% n 50% gi tr d ton, ty thuc vo s tin tng ca bn v cc d ton ban u ca bn. Hp ng cng phi c iu khon ni rng hp ng s ti thng lng nu c s kin ngoi mun nh mt s thay i ln trong khch hng thay i cc yu t; V d; thay i cc yu cu, tin , hoc ti tr, c th l thay i phm vi d n.6.4 Thit k cc rng buc d n.Qu trnh c lng c minh ha trong hnh 6.1 c p dng kh cc thuc tnh sn phm nh kch thc v phc tp c s dng c lng thuc tnh i tng nh l s n lc v thi gian. Trong trng hp ny, cc thuc tnh c rng buc bi cc yu t ca sn phm. trong mt s trng hp, s n lc hoc lch trnh hoc cc thuc tnh cht lng c quy nh nh rng buc d n v c s dng c lng cc thuc tnh sn phm c th c pht trin hoc sa i trong nhng rng buc. Cch tip cn ny c gi l thit k rng buc cho d n.Gi s, v d, mt d n phi c hon thnh tng 6 thng bng 5 nh pht trin phn mm (30 nhn vin/thng n lc). S dng quy tc ngn tay ci t pha trn, n l c tnh rng 30 nhn vin / thng n lc s dn n 15000 DSLOC (30x500) v rng s lng cc khim khuyt l 150 trc pht hnh v 15 sau pht hnh.Thit k ny c tnh cc hn ch da trn yu t nng sut v l gi nh in hnh ca t chc (500DSLOC/SM). Nu cc sn phm tng lai c tnh c ti 20.000 DLOC, 5 thnh vin i d n s phi c 33% nng sut cao hn trong qu kh nu h hon thnh d n trong 6 thng.

Hnh 6.3 Thit k rng buc d nTnh kh thi ca d n ph thuc vo quy nh mt hoc nhiu yu t iu chnh hn tng nng sut ln 33%; v d, d n c tnh kh thi nu bn s dng 5 trong s nhng ngi pht trin gii nht ca t chc. Nu bn khng gi nh rng mt s yu t thc t iu chnh s l s tht, cng vi s tin tng cao, c mt nguy c tng ng cho s tht bi d n. Nu kch thc sn phm c c tnh l 30000 DLOC, th i d n s phi sn xut gp i so vi i tiu biu. iu ny l khng ph thuc cho bt k kch bn no, v ch ra hn ch d n l khng kh thi.Bn phi cn trng rng nhng hn ch d n khng lm cho n khng th tm thy gi tr i vi cc yu t c tnh. C mt cu ni :bn c th c mt phn mm sm, tt, gi r , chn 2 ci bt k. Nu bn mun phn mm ca bn sm v tt th n s khng r, nu bn mun phn mm tt v r th n s khng th xong sm.Tnh hung ny c minh ha trong hnh 6.4a v 6.4 b nh 3 thng s tin , ngun lc v yu cu, chng phi c cn bng. Nh nu, c mt s tnh d sai trong mt hoc nhiu kch thc : c th c mt s d phng trong lch trnh. C th s c mt gii hn trn cc ti nguyn c th c p dng cho d n. C th c ti thiu c ngha l d n c tnh kh thi, tr khi cc ngun lc ti thiu c sn, s c s lng ti thiu cc tnh nng v cc thuc tnh cht lng phi c chuyn giao.Mc tiu c bn ca c lng l n pht trin v duy tr c tnh gi cho d n ca bn trong hp gii php lc ban u v khi iu kin thay i. Gi cho d n ca bn trong hp ngha l bn s cng cp mt sn phm c th hi lng p ng y cc yu cu c bn(yu cu mong mun v yu cu bt buc) trong gii hn chp nhn c v mt lch trnh sn c ngun lc. Kt thc d n ca bn ti bt c im no trong hp ch ra rng bn a ra sn phm c th chp nhn c trong thi gian v ngn sch.

Hnh 6.4a : Ba bin c bn d ton v kt qu l hp gii php.

Hnh 6.4b : Hp vn rng buc trong hnh 6.4aMt d n qu hn l mt d n khng c gii php kh thi trong hp hoc mt phng hoc im n. Kt qu ca tnh trng ny khi hn ch v lch trnh t hn so vi thi gian c tnh cn thit hoc ti nguyn t hn s lng nh nht ca yu cu, iu c th thc hin trong nhng hn ch ca lch trnh v ngun lc so vi cc hng mc thit yu. Cc rng buc cng nhc 1 hoc 2 ca 3 bin c bn i hi tnh linh hot trong 1 hoc 2 thit lp tnh kh thi ca gii php im. Rng buc cng nhc hn ch tt c 3 bin thng l cng thc cho s tht bi.c tnh i khi l bt buc. Nhng c tnh l kt qu ca cc rng buc d n v yu t sn phm khng c tnh linh hot trong d ton cc thng s.(v d, nhm ca bn c 5 nh pht trin phi pht trin 60 000 dng, cht lng code trong 6 thng; n phi tt, gi r v sm). y khng phi l d ton; n l mt thm ha sp xy ra cho bn, cho d n, cho t chc ca bn.6.5 Kch thc c tnh sn phm :Ch ra nh hnh 6.1, d on cc yu t nh n lc, tin , ti nguyn, chi ph, v thuc tnh cht lng a da trn c tnh thuc tnh sn phm, rng buc d n, kinh nghim qu kh, v iu chnh cc yu t. Ngoi ra, hnh 6.3 ch ra nhng hn ch ca d n c th quyt nh cc thuc tnh ca mt sn phm c th c xy dng hoc sa i theo nhng rng buc.Hu ht cc m hnh thut ton, cng c, v cng ngh s dng mt s phng php kch thc nh thuc tnh sn phm c bn da trn cc c tnh hoc trng hp thit k rng buc sn phm. kch thc thuc tnh sn phm c c tnh. Ty theo tnh cht ca sn phm, cc yu t v thm kch thc, nh vy phc tp ca sn phm, mc kt ni, thi gian thc cn thit hoc s lng d liu c thao tc, c th nh hng n d ton cng sc, thi gian, ngun lc, cc yu t cht lng v chi ph; cc yu t sn phm b sung nh th c bao gm nh l h s iu chnh trong hu ht cc m hnh d ton.Hu ht cc phng php c lng da vo cc yu t sn phm s dng mt s bin php kch thc sn phm nh yu t chnh m cc a c tnh bi v : Kch thc c mt mi quan h nhn qu mnh m cc thuc tnh n lc v lch trnh d n hn cc thuc tnh sn phm khc. Kch thc c th c o lng mt cch khch quan hn cc thuc tnh sn phm khc. Mt s bin php kch thc c th c tnh chnh xc hn t cc yu cu c th ca cc thuc tnh sn phm khc. D liu kch thc, n lc, k hoch v thuc tnh d n khc c th c thu thp t vic hon thnh d n v c lu tr trong c s d liu d cung cp c s lch trnh lp d ton cho cc d n trong tng lai. Trong lch s, dng chuyn m (DSLOC) c s dng nh kch tc o lng nhng c mt s vn lin quan n cch s dng dng lnh : Rt kh c tnh dng m ban u trong mt d n; rt kh thay i cc yu cu trong c tnh dng m. Tnh ton nng sut nh dng m c to ra cho mi lp trnh vin/ thng c th khuyn khch cc lp trnh vin vit rt nhiu dng m cht lng cao. Cc phng php php trin hin i nh m hnh hng pht trin, i tng da trn lp trnh, ti s dng th vin v s dng ngun m cc thnh phn lm cho mi quan h gia dng m v cc thuc tnh d n t ph hp v t chnh xc so vi trong qu kh.Cc bin php kch thc khc vi dng m d c pht trin khc phc vn ca vic s dng m. Chc nng ca cc kch thc im l tt nht c bit n v lch s ln u tin thay th cho dng m. Hm s im c tnh bng cch m s lng ca cc loi yu t u vo khc nhau, kt qu u ra, tp tin ni b, truy vn giao din trong mt h thng phi c c tnh. Cc tnh ton da trn quy tc m khch quan v duy nht u vo, u ra, d liu ni b, truy vn, v giao din l n gin, bnh thng hay phc tp.Cc m hnh im chc nng c minh ha trong hnh 6.5. Cc gi tr trng s c tng kt cung cp mt s chc nng iu chnh im (UFPs). H s iu chnh nh s phc tp ca x l, giao dch t l v d dng theo yu cu s dng sau c p dng gii thch cho iu kin yu cu nhiu hn hoc t hn s n lc hn d n in hnh. Thng tin chi tit v mt v d v c lng chc nng im cung cp trong thanh i km. Nh ch ra thanh bn, phn tch im chc nng c khi qut tr thnh phng php kch thc chc nng.

Hnh 6.5 : Tnh cc yu t im chc nng.Mt kha cnh th v ca kch thc im o chc nng l cc dng m yu cu thc hin mt s lng nht nh cc im chc nng ph thuc vo ngn ng lp trnh c s dng thc hin phn mm cn thit x l cc yu t u vo tp tin, giao din v truy vn, kt xut kt qu. N c th l, i vi mt t chc v mt loi c bit v kch thc ca sn phm m cc yu t chuyn i t im chc nng thnh dng chuyn giao ca m l 50 DSLOC/FP cho cc chng trnh vit bng java v 300 DSLOC/FP cho cc chng trnh tng t c vit bng ngn ng assembly.iu ny s ch ra rng Java l 6 ln thi gian hn so vi ngn ng assembly cho mi loi hnh v kch thc sn phm trong t chc ny. Nu n c gi nh rng n lc cn thit vit, ni, 100 dng m c lp vi ngn ng chng trnh c s dng. Ngi lp trnh Java s c 6 ln nng sut cao hn cc lp trnh ngn ng assembly c o bng phng php im chc nng trn mi lp trnh vin mi tun hoc mi thng.Cc vng loi trong on trc cho mt t chc c th v loi c bit v kch thc sn phm l quan trng bi v t l dng m hot ng im l khc nhau cho cc loi khc nhau ca phn mm, vi nhiu kch thc khc nhau ca phn mm, v cho cc t chc khc nhau. Mc d hng dn c cng b chuyn i im chc nng thnh dng m cho cc ngn ng lp trnh khc nhau, vic chuyn i nhiu yu t nn c ngun a phng. Trong t chc ca bn, bn c th c nhiu yu t chuyn i khc nhau cho cc loi v kch thc sn phm phn mm khc nhau, v cc yu t chuyn i c th khng c gi tr cc b phn khc ca cng ty.Yu t chuyn i gia cc im chc nng v dng m l hu ch :1. im chc nng s dng nh l u vo c lng cc cng c c iu chnh cho dng m.Php o kch thc hm.o kch thc hm theo im l thc o kch thc u tin (FSM); pht trin bi Alan Albrencht vo gia nm 1970s o kch thc bn ngoi ca ng dng x l d liu. ng gi phng php tip cn phn tch im chc nng (FPA). Nhm The Function Point International Users (mt t chc phi li nhun) by gi l ngi nm gi chnh thc FPA. IFPUG duy tr cc chc nng m im thc hnh, nm gi cc hi ngh hng nm v ti tr cho cc cuc hi tho gio dc. IFPUG cng cung cp mt chng ch chuyn nghip cho chng trnh chng nhn chuyn gia im hm.

Bng 6.1 : v d im hmBng trn minh ha cc phng php chc nng theo im o kch thc chc nng. V d trong bng cho thy s lng cc chc nng im cho cc u vo, cc kt qu u ra, tp tin , truy vn, v cc giao din(in m) v cc yu t trng s n gin, trung bnh v trng s phc tp. iu ny ch ra nhiu n lc yu cu pht trin hm cho tp tin v giao din hn ba yu t khc.Nh nu trong bng 6.1, s lng cc chc nng im cha iu chnh(UFPs), v d nh 242. Nu cc yu t iu chnh tng hp l 1,13, s lng cc im chc nng iu chnh l khong 276 (1.13 x 242) . Nu d liu lch s ca qu kh ch ra nng sut 6,5 chc nng im cho mi cn b/thng (6,5 FP/Sm) d ton s n lc ny l khong 42 nhn vin/ thng (c th c tnh 6 ngi trong 7 thng).Mt s phng php o kch thc hm khc c pht trin. Phng php im chc nng m cc yu t ngoi rt quan trng vi kho d liu - ng dng chuyn su; Phng php im chc nng b sung thm mt s thut ton tnh ton h thng tp trung [Jones86] . MK II im chc nng ci thin v s lng chc nng im theo tp tin v tnh ton tt cho phn bn trong ca d liu - ng dng phong ph.Nm 1998, COSMIC (the common software measurement international) c thnh lp bi mt nhm lm vic ca t chc tiu chun quc t (ISO) cho mc ch pht trin v pht hnh tiu chun ISO cho php o kch thc hm, m l mt s tng qut ca phn tch im chc nng.COSMIC FFP (ISO 19761) l mt phng php o lng kch thc chc nng khi qut qu trnh o lng gii quyt cc vn h thng thng tin qun l cc vn , cng nh thc t d n thi gian v phn mm lai. N ph hp vi cc tiu chun ISO v o lng kch thc chc nng v ch s dng FURs ca d n phn mm l u vo cho tin trnh php o.2. chuyn i d liu lch s cho cc d n da trn dng m cho d liu lch s da trn im chc nng.

Bng 6.2 : V d v o lng kch thc ngoiBng 6.2 lit k mt s v d v cc bin php kch thc theo FPA. Nhng bin php ny l cc bin php kch thc ngoi (ESMs). Cc thut ng chung cho cc phng php n v l kch thc n v ngoi (ESUs). im chc nng nh l mt ESM, v s lng im chc nng trong h thng phn mm hoc sn phm l ESUs. Thut ng ny c s dng bi tiu chun ESMs o cc yu t bn ngoi cc phn mm c pht trin hoc sa i bao gm :1. u vo phi c p ng2. u ra phi c chuyn giao3. Giao din th ngBa yu t quyt nh kch thc bn ngoi ca phn mm , cng vi cc yu t chuyn i v cc yu t iu chnh, c th c s dng c tnh cc yu t. Chng hn s lng n lc cn thit , thi gian cn thit, mt pht hnh li v cc khim khuyt sau pht hnh, tin cy. Nu cc quy tc sn xut ca ngn tay ci, xc nh t cc d n trc y, l 7 im chc nng cho mi nhn vin / thng.(7 FP/SM). Cc d n c m t trong bng 6.1 s yu cu khong 35 nhn vin / thng n lc (242/7).Da trn nhng cn nhc, gi thit sau y cho kch thc bn ngoi cc bin php c cung cp : Cc ESM :lun lun c th tm thy mt thc o bn ngoi m c th s dng c, cng vi d liu v iu chnh yu t lch s, pht trin cc c tnh ca cc thuc tnh ca d n quan tm.Mt gi thit l mt tuyn b c cho l ng nhng khng th chng mnh n ng. Cc gi thit lun lun c th b bc b bi mt phn chng duy nht. l nhng phng on nn s ng da trn quan st mc ch ca cc phn mm l x l u vo, tng tc vi h thng khc, sn xut kt qu u ra. Do , cc phn mm c pht trin t l thun vi s v loi u vo, u ra v cc giao din c x l bng cc phn mm , c o bng ESM. Minh ha trong hnh 6.6

V d, gi s bn pht trin mt ESM cho phn mm nhng s dng cc thng s sau :u voS on, IS cp u tin, PGiao dinS mc bng iu khin, Eu raS tn hiu, SGi s bn pht trin cc d liu sau t d liu lch s:ESUs = 2I + 4P + E + 5S.Cc yu t quan trng ch ra s n lc tng i cn thit thc hin cc m x l cc on m , x l mc u tin, bng iu khin truy cp, v to ra cc tn hiu u ra. Mt h thng c 5 on khc nhau 3 mc u tin, kim sot 15 giao din bng, v 15 tn hiu khc nhau s c 112 ESUs. N lc = = 56 nhn vin / thngD n c th c tin hnh s dng 6 nh pht trin phn mm trong 10 thng.Nu bn quan tm n rng buc b nh, bn phi phn tch sn phm c pht trin mi quan h dng :Bytes = x * ESUTrong x l s chuyn i Bytes/ESU. Cc yu t khc c th c tnh theo cch tng t.Bc cn thit pht trin mt ESM c lit k trong thanh nh km.Cc k thut khc nhau c lng cc thuc tnh c quan tm ca d n phn mm(n lc, tin , ngun lc, thuc tnh cht lng v chi ph) c th c phn loi nh thc t, c s l thuyt. K thut c lng thc t bao gm: Quy tc ngon tay ci. Tng t Phn on ca chuyn gia WBS/CPM/PERTL thuyt c s c lng bao gm : ng lc h thng. SLIM Hi quy da trn m hnh d ton bao gm : COCOMO Cc m hnh c ngun gc cc b.M hnh c s l thuyt v c s hi quy da trn s dng kch thc nh d on s cp u vo. K thut thc t c th hoc khng d dng bin php kch thc. Bn cht ca cc phng php v v d v s dng c th hin trong phn sau.Pht trin phng php kch thc ngoi:phng php kch thc ngoi cho h thng hoc sn phm tng t c th c pht trin nh sau :1. Phn tch mt s im tn ti ca h thng v sn phm tng t ti h thng v sn phm c pht trin :a, xc nh mt s ESUs c tnh trong mi trng h thng hoc sn phm.b, pht trin quy tc m cho ESUs2. Hiu chnh ESM nh sau :a, m ESUs cho mt s h thng tn ti;b, pht trin trng s cc yu t cho ESUsc, p dng trng s cc yu t vo iu chnh ESUs sn phmd, pht trin cc yu t bin i t kch thc n v ngoi phi c c tnh.f, p dng cc yu t bin i tnh ton cc yu t phi c c tnh.g, so snh c tnh n gi tr thc t cho cc d n trong qu kh.h, iu chnh cc yu t trng im cho ESUs v pht trin cc yu t bin i v m cc bin th trong yu t c tnh cho h thng lch s c ESUs tng t.3. Lp li bc 1 v 2 cho n khi m hnh ESM ca bn tha mn tiu ch sau : Cc ESUs c m ti cc yu cu v giai on thit k ban u ca d n ca bn. Cc ESUs c trng cho cc phn mm c thc hin, Cc yu t bin i c th c bt ngun iu chnh bin i ESUs c lng. Tiu ch 3 nn h tr c lng ca cc yu t nh : c lng : LOC = AESUs x () c lng n lc = AESUs x () c lng cost = AESUs x () c lng defects = AESUs x ()LOC l nhng dng code.LOC /ESU, Effort/ESU, Cost/ESU, Defects/ESU thu c t d liu lch s cho cc d n trong qu kh; v AEUSs c iu chnh ESUs cho d n c tnh, iu chnh bi cc yu t iu chnh ca d n.6.6 K thut c lng thc t.K thut c lng thc t khng da trn cc m hnh l thuyt cng khng phi trn phn tch hi quy. H chng minh l hu ch trong thc t mc d khng c l thuyt hay nn tng hi quy. Mt s k thut thc t c m t trong phn ny.6.6.1 Lut ngn tay ci.Lut ngn tay ci (ROT) l mt hng dn chung c chp nhn. Bi v k thut phn mm khng ging nh cc ngnh k thut khc, khng i ph vi thc th vt l, chng ta thiu rt nhiu m hnh ton hc v da vo k thut truyn thng. Do , chng ta s dng nhiu lut ngn tay ci, mt s chng l ton ngnh( v d, thng thng, n c gi t 50 n 100 ln sa mt sn phm pht hnh khim khuyt hn mt sn phm li pht hnh li) mt s c ngun gc chuyn i. (v d, chi ph gp 75 ln i vi sn phm li giao din so vi li trc khi pht hnh.)Yu t nng sut s dng trong phn v d 6.3 (500 DSLOC/SM) c th l mt nguyn tc ngn tay ci i vi mt loi phn mm c trng.(V d, ng dng khoa hc, x l d liu hoc vin thng) hoc c th l loi phn mm.Khi bn s dng s liu nh 500 DSLOC/SM hoc 5 FP/SM , bn phi hiu yu t bao gm trong s liu . s liu nng sut, v d, c xc nh bng cch m dng m trong sn phm c, xc nh nhn vin / thng cn thit to ra nhng dng v hnh thnh t l ( v d 500 DSLOC/SM). Bn phi hiu lm th no kch thc c tnh v phm vi ca s n lc c bao gm s dng s liu nng sut. m dng m c th bao gm: Dng m assembly trong modun ti ca chng trnh. M ngun khng c comment M ngun vi cc comment Dng ngun, bao gm comment v cc th vin Tt c code c ti s dng, m ngun m v m mi trong sn phm cui cng Tt c bn trn cng vi tt c cc th nghim.S n lc c th ch cho vic code, code v test, hoc tt c hot ng pht trin phn mm cng qun l d n, ci t h thng, v training ngi s dng. N c th bao gm tt c cc thi gian cc nh pht trin phn mm, bao gm c thi gian h tri qua trong cc cuc hp lin quan v duy tr phn mm khc. N c th c ghi nhn 40 gi mi tun trong khi thc t cc nh pht trin ang lm vic 60 gi mi tun.Cc d n m quy tc ngn tay ci l c bn c th c c d liu, tin trnh ng dng, thi gian thc h thng nhng, hoc c l da trn web, ng dng thng mi. Cc d n c th trng by cc s liu tng t t cc gi tr trung bnh h c thc o tt s dng hoc cc gi tr thay i nhiu. Do lm cho quy tc ngn tay ci ca h khng ng tin cy.Khi bn p dng quy tc ngn tay ci thc hin mt c lng, bn ang c tnh phm vi cng vic, cho mt d n tng t, bao gm cc dn xut ca ROT. Nu mt ROT nng sut 500 DLOC/SM da trn s n lc vit nhng dng nhng m assembly v pht trin 60 gi mi tun. Bn c tnh nhng n lc cn thit vit, cc c tnh ca nhng dng assembly khi ngi pht trin lm vic 60 gi / tun. Mt quy tc nh cho pht trin h thng nhng h thng thi gian bng cch s dng ngn ng C c l khng p dng i vi cc ng dng kinh doanh s dng COBOL.Trng hp khc, bn phi xc nh rng cc ROT l cho cng mt phm vi kch thc sn phm nh kch thc c tnh ca bn. ngay c i vi cc loi t t nh sn phm v h thng, vic chuyn i s dng lin quan n kch thc yu t n lc thng l phi tuyn. v vy, mt n lc c tnh da trn mt ROT cho cc sn phm c cha 500 im chc nng c th tng ln bi mt yu t 1.5 hoc nhiu hn cho cc sn phm ca 1000 im chc nng.Ngoi ra, bn phi hiu c nhng bin th trong kinh nghim qu kh c s dng d ly c quy tc. v d, ROT ca bn da trn 5 d n trc y c kch thc v n lc, tnh theo cch tng t, sn xut mt ROT trung bnh 5 FP/SM nhng ROTs cho 5 d n c nm trong khong 3,5 FP/SM n 7 FP/SM . Bn phi hiu cc yu t dn n cc bin th, s dng cc d n tng t nh hu ht cc d n ca bn. Mc d cc d kin da trn quy tc ngn tay ci l hu ch cho : Cung cp kh khn nhm d on ln. H c th c s dng khi thc hin nghin cu tnh kh thi v kch bn.6.6.2 Tng t :Tng t l k thut s dng cng ngh d on thuc tnh d n trong k thut phn mm v cc ngnh k thut khc. Mc tiu ca s tng t da trn d on tm mt hoc cc d n tng t nhiu hn m cc thuc tnh quan tm c bit n. Cng gn tng t, cng tin tng hn, bn s c d ton ca bn. Bn c th tin tng hn vi d n tng t d n bn ang c tnh.Tng t - c s c tnh c th c n gin (mt d n yu cu 5 ngi cho 6 thng) hoc tinh vi. Trong trng hp sau, t chc ca bn c th c mt c s d liu quan h ca d n trong qu kh. Mi hng trong lc d liu s cha d liu cho mt d n hon thnh. Mi ct s ghi li cc thuc tnh ca d n qu kh. Chng hn nh : Khch hng Loi sn phm Phm vi hot ng bao gm Kch c sn phm v phng php kch thc s dng iu chnh cc yu t s dng M hnh pht trin s dng Cng c pht trin s dng c lng thi gian d kin v thc t c tnh v n lc thc t c tnh v chi ph thc t S khim khuyt trc v sau pht hnh Vn gp phi, Bi hc kinh nghim thc hin mt c tnh, bn s xc nh cc c im c bit n ca d n bn ang c tnh. Sau bn s vit mt truy vn ly danh sch cc d n ph hp vi d n ca bn trong phm vi c bit. v d, tt c cc d n pht trin cc sn phm phc tp cao v nm trong phm vi chnh lch 10% kch thc c tnh ca bn, c xy dng vi cc k s c k nng trung bnh s dng C++ v m hnh xy dng.Sc mnh chnh ca tng t - da trn c tnh l : Cung cp c s d on cho d n ca bnim yu chnh l : Suy din sai lm khin c tnh khng chnh xc.c tnh khng c tt hay xu hn so vi tng t m n da vo.

6.6.3 Nhn nh chuyn gia

Nhn nh chuyn gia lin quan n vic yu cu mt hoc nhiu chuyn gia cho d ton ca h v cc thuc tnh d n nh s n lc, thi gian, trnh k thut v cc yu t ri ro. Hnh 6.1 lu tr d liu trong u ca mt hoc nhiu chuyn gia. Vic iu chnh cc yu t m h p dng c th bao gm cc yu t ch quan nh bit ngi s lm cng vic v qun l cng vic, cc yu t chnh tr quan h khch hng v xch mc c th tn ti gia cc yu t ni b ca t chc. Thuc tnh sn phm bao gm bt k thng tin c sn cho cc chuyn gia kim tra.Cc chuyn gia c th cho bn bit rng cc yu cu qu m h v khng y vi chng a ra mt quan im( l hu ch bit). mt thi cc khc, khc nhau ca nhng ngi chuyn gia c th cung cp d ton cho cc yu t khc nhau ca kin trc ca vic hnh dung ra h thng hoc sn phm(v d, giao din ngi dng, cc c s d liu, cc gi thng tin lin lc, cc thut ton) Cc th mnh chnh ca chuyn gia d on rng : S khc nhau gia nhng chuyn gia c th cung cp c lng cho nhng b phn cu thnh ca cc sn phm khc nhau. Chuyn gia c th bao gm cc ch v cc yu t chnh ch m khng lu d trong c s d liu d n c.Cc im yu chnh l : Cc chuyn gia c th qu lc quan trong vic c lng thi gian, ti nguyn cn c h lm vic ch khng phi l thi gian v ngun lc cn thit bi bi t cc chuyn gia pht trin. S hi tng ca h v nhng kinh nghim trong qu kh c th khng chnh xc hoc khng y .

6.6.4 Cng ngh delphiBn c th s dng cng ngh Delphi c lng tng hp t cc chuyn gia khc nhau. Mi chuyn gia c a ra cng mt thng tin lin quan n sn phm tng lai (v d, yu cu hot ng, thng s k thut, quan im kin trc, rng buc) Mi ngi c yu cu cung cp c tnh ca cc thuc tnh d n v l mt nh gi ngn gn cho c tnh ca h. Mi chuyn gia c th p dng cc quy tc ngn tay ci, loi suy, nhng nh gi ca h, hay l thuyt, m hnh hi quy khi h chn pht trin c tnh ca mnh.Bn, ngi iu phi, tng hp cc d ton ca h, cung cp cc kt qu tng hp li h cng thm bt k thng tin b sung no m h c th yu cu. v yu cu h cung cp d ton ln 2. Phn hi th in t, s dng mu d ton hon thnh v gi li, l mt cc thun tin cho qu trnh Delphi. Mt v d l chuyn gia ln 2 on c cung cp trong hnh di.

D n : h thng ATM.D on lt : 2Ngi d tnh : Sue SmithLt 1 d on t 4 chuyn gia

Tng hp nh gi t lt ngi c tnh 1 n 4 :1. Ti khng thy bt k vn ; nn lm nh d n thng thng.2. Cc yu cu l khng r rng trong mt s lnh vc; c th gy ra vn 3. Giao din phn cng c th gy ra mt s vn .4. Ngi ca chng ta c nhiu kinh nghim vi cc loi h thng.Lt 2 c tnh : 35 nhn vin mi thngLt 2 nh gi :Ti khng ngh yu cu khng r rng s l mt vn bi v ngi ca chng ta c nhiu kinh nghim vi cc loi h thng v kinh nghim lm vic vi khch hng. Ti ang tng s c tnh t 30 35 nhn vin mi thng bi v giao din phn cng cp trong 3 nh gi.

Khong thi gian gi d ton gi nn l 1-2 ngy. iu ny cho php mi chuyn gia c thi gian phn nh trn cc bo co tm tt t vng trc, nhng khng qu nhiu thi gian m h qun cc chi tit hoc mt hng th trong qu trnh ny. Cch tip cn Delphi du tn kt hp nhng u im ca nhiu kin chuyn gia trong khi trnh nhng bt li ca khng ph hp hoc thuyt phc bi mt hoc nhiu chuyn gia.D ton c th khng tp hp sau 3 hoc 4 vng(Vng 3 l in hnh ca cng ngh Delphi). Nu cc c tnh hi t phm vi hp, mt cuc hp gia cc chuyn gia c triu tp xc nhn cc d ton ca h v ghi li bt k mi quan tm h c th c v cc d n xut. nu d ton ca h khng hi tu, mt cuc hp c t chc cho php h bin minh cho d on ca h v gii quyt nhng khc bit gia mi ngi. Nu c tnh ny khng hi t trong cuc hp, phm vi d ton c th c s dng pht trin mt hm mt xc sut cho cc c tnh.Mt phng php khc c gi l qu trnh bng rng Delphi. Phng php tip cn ny lin quan n vic triu tp mt cuc hp ca cc chuyn gia hng u tho lun d n, cho php thi gian phn nh v qu trnh d ton n danh, t chc hp sau mi vng ca d ton tho lun cc gi nh v l do d ton ca h. C mt s mi nguy him m mt s c lng c th qu mc nh hng n ngi khc v c tnh hay v tr quyn ca h, nhng mi c lng c thi gian suy ngh thm v cuc tho lun v lm nghin cu thm trc khi d ton tip theo ca h, nhng bo co n danh.Mt cch tip cn trit hn l mt ni m qu trnh ny hon thnh trong mt cuc hp. mi t d ton c thc hin bng cch b phiu kn vi cuc tho lun v d ton gia cc vng. iu ny c th c thc hin mt cch hiu qu, c bit l nu iu kin bi mt nhm cng c phn mm cho php mi chuyn gia n danh nhp c tnh v bin minh ngn gn t bn phm ca h. Mi chuyn gia d ton v bin minh l n danh c hin th trn mn hnh ln nhm quan st v cung cp cc c s ca cuc tho lun gia cc vng d ton. Cch tip cn ny hiu qu hn Delphi truyn thng hoc bng thng Delphi , nhng n khng c khuyn khch v n khng thi gian cho cc chuyn gia suy ngh v cc kt qu vng trc, c th lm mt nghin cu trong vic chun b d ton tip ca h, v trnh cc nh hng ca nhng ngi khc trong phng.Mt qu trnh Delphi c th hoc khng th to ra mt kt qu ng thun. Tht bi trong vic t c ng thun c th ch ra s cn thit trong cng vic tip theo phi c thc hin vi khch hng v qun l ca bn vo cc tinh chnh cc yu cu, kim tra cc hn ch thit k, nh gi tnh kh thi ca d n. Mt cch khc s dng kt qu khng hi t pht trin mt hm xc sut t phm vi d ton v s dng n phn tch ri ro nh lng s dng mt m hnh xc sut. Cc th mnh ch yu ca qu trnh lp d ton Delphi : C kin kt hp ca cc chuyn gia m khng nh hng thi qu ca cc c tnh ca cc chuyn gia khc nhau. Nhiu vng d ton, trong mi chuyn gia phn nh trn mt n danh l do c bn trnh ca ngi khc.im yu ca qu trnh lp d ton Delphi : Thi gian v cng sc yu cu ca chuyn gia Kh nng khoan nhng bi mt hoc nhiu chuyn gia Kh nng nh hng thi qu trong cc cuc hp wideband Delphi 6.6.5 WBS/CPM/PERT

WBS/CPM/PERT cch tip cn c lng da trn s thay i cch nhn kin trc gn vo WBS v cc gi cng vic WBS. Gi cng vic c th c s dng cung cp cc d ton di ln cc thuc tnh d n bng cch lp li d ton mc thp cho cc hot ng v nhim v. Gi cng vic d ton c th da trn k thut thc t khc hoc da trn c s l thuyt hoc m hnh hi quy.Vn ny, WBS/CPM/PERT c cch tip cn c l chnh xc nht trong cc k thut thc t v mc tng ca chi tit khc nhau m k thut c lng c th c p dng v v bin tch cc v tiu cc trong s thiu chnh xc mc thp c th ra trung bnh khi tng hp mc cao hn. Phng php PERT c th c s dng cung cp cc phn b xc sut cho lch trnh di hn t c mc khc nhau hon thnh d n.Bn c th khng chi tip pht trin ADV , mt WBS , gi cng vic, v quan trng l ng dn mng lch s sm trong trong d n ca bn. nhng vic pht trin cc mc phi l u tin hng u trong k hoch v lp li k hoch. iu chnh d ton da trn kt qu ban u nn c thc hin cng sm cng tt. WBS, v lch trnh mng s tr nn chi tit hn nh s hiu bit v pht trin nh thc hin cc tin trnh d n . c tnh cp nht da trn pht trin WBS v tin mng cn c chun b trn c s lin tc. im mnh chnh ca cch tip cn WBS/CPM : Tnh chnh xc ca cc c tnh tng l kt qu t mt mc tng ca chi tit v mc km theo ca s hiu bit.im yu ca cch tip cn WBS/CPM : Thiu kin thc y hoc thi gian chun b cc ADV, WBS, gi cng vic, v mng li ng dn quan trng trong giai on lp k hoch ban u ca d n phn mm.