2001年度日本オペレーションズ。
リサーチ学会春季研究発表会
1−C−2
So托wa陀Ava温はb温風i七yÅma且ys鼠s C⑬mSider亙mg
Im七e町mi軌em七乳Jse
O1307475 鳥取大学 *得能貢一 TOIくUNOKoiclli
O1702425 鳥取大学 山田茂 YAMADAShigeru
1Int.roductioll
Wediscussthcsoftwarc‘乱VailabilitymodelillgWllellthesystemisuscdi11termittently.Fl・Omthcviewpoillt
Ofusers,OCCurrellCeOfa・SyStemhilureisrecogllized
whellthe event that cither a software failure occurs
WhenthesystcmisilluSeOrauSagedemandoccurs
When thesystemis ullder restoratiollal・ises.In this
paper,a COuPle of new measures fbr software avaiト
ability assessmcnt are derived;these arc callcd the
disappointmelltl)rObabilitiesinuseandunderrcstoraLr
tion,reSpeCtively【1,2]・Itissupposed thattheus−
agedemandofthcsystemoccursrandolnlyandthat
t.he user’s demall(1t,i111eis also random.The timc−
depelldclltbehaviorofthesystemalterllatingbetwcell
up and down sta七esis described by a Markov plてト
CeSS[3]・Thenthesoftwarcreliabilitygrowthprocess,
the upward tendcllCy Ofdi瓜cultyin debugging,alld
theimperfectdebugglllgellVironmelltarealsocollSi(1−
ered.
2 Modeldescriptiom
Tl■1e followillg往SSU11■11)tiollH al・(=11a・(le bl・SOftⅥ′礼re availEt・bilitylnO〔lclillg:
Al.TlleSOftwarcsystemis u11aVailable al’1(lstnl・tS t()
bel・eStOred ftS SOOllflS aSOftwarc hilureoccurs,
alld thcsystclll(:al111OtOl)el・ate untilthcl・CStOl・a−
tiolla・Ctiollis(:0111l)1etc・
A2.TlleSyStCnlis11Otil■111SCEt・ttimcI)OilltZCl・().Tll(†
timetooccurl・(一11CCOfil・uSagCdcl11a・n(1,X,a11dtllC
usagcl)Crio(1.Y,followexl)011C11tin・1(1istl・ibutiollS
withmoa11Sl/Oan(11/17,rCSl)e(:tively■ A3.TllCl11)tilll(、(tll(一tilllet・OfllSOftwal・(1fとILihlrC),Z。, n・11(1tlle doⅥrlltil11e(tllel・CStOl雨iol−tilll(−),ソ1, bllowぐXl)011Clュtial(listl・il)utiollSWitlllllOn・11Sl/l。 a・1■1(11ルn,1・eSl)(−(:ti\′Clさ′,WllCl・(川・(】cllOtぐStllC(=lト11川htil′(=1日Hlbel・(JfH)1・1・eCtC(=h吊h.ん7肌1(=ノ′.
n11・Cdecrc礼別11gfull(:tiollHOf捏. A4.TllereStOl・a・tiollil」(:t血Iil叩hcstlle(ld川ggillgil・ト tiヽ両′;tllisiHl)(汀hl・111(−(11)Cl・k(叫′Ⅵritlll)1・()bil・bilト tya(0<a≦1)‡l・11dil一一1)el・hctlywitl11)rObabilityb(=1−a)・011Chultisremoved fromthesoft−
WareSyStelnWhenthcdebugg111gaCtivityisper−
fbct,andthenthesoftwarcreliabilitygrowthand
theupwardofdifBcultyilldebugglllgOCCur.
A5.Theusagedelna・11dsoccurl・1ngWhe11thesystemisrestored are cancelcd.
ConsiderastochasticI)rOCeSS(X(t),t≧0‡whose
StateSpaCeis(W,U,R)definedasfollows:
Ⅳ=(町l;托=0,1,2,…)
tlleSyStemisavailablebutnotused,
ぴ=(坊1;7l=0,1,2,…)
thesystemisavailableand used,
虎=(見れ;†l=0,1,2,…)
thesystemisrestorcdduetoasoftwarefailure.
n・0111aSSulnPtiorlA4,WllClltllel・eStOratiollaCtiol1
11aSbe(−n(:Oll−1)1eteil−(ズ(り=軋), 〈 珊= . (1)Figurelillustl・ttteS tllSEul11)lc state tl・allSition dia− gr礼nlOrズ(け
3 ]Derivaもion ofmeasures
Thc・舶Ite OC(:upn・1−Cyl)rOl)n・bilitiesll・l・,,,(t)≡ Pl・(ズ(t)=lγn),巧/一.(り ≡ Pl・(ズ(り = ぴn),a・11(l PR..(t)=Pr(X(t)=R,..)Ⅲ11l)e Obtftil−e(1fu−a・1yti− (:il・ll)′,all(1itis(lcllOt(−(ltl‘1n・t (X)Pl・(ズ(り∈Ⅳ)≡∑恥‖(f),
Jl=O nOPl・(ズ(り∈U†≡∑軋(り,
丹==() (■X〇Pl草(f)∈呵≡∑巧子‖(り,
lIニこ0 (2) (3) (4) 1・CSl)C(:tively.Tll(一11tll(一1)1・Obil・l)iliti(一S tll血il・SOftwn・1て、 f;l・il11l・eO(:(:llrSWllCllthesystolllisl】SC(liuldtlln・tn・uSn・gC−52 −
© 日本オペレーションズ・リサーチ学会. 無断複写・複製・転載を禁ず.ん什l△T
Fig・1Asal−1Plestatctral−Sitiol−diagl・al110fX(t).
in Use Notin Use Up/DownSlatc Or Sysle■¶ i11Use Nolin Usc Up/DowIISlale Or Sysle111 J (ズ(り∈〃)+:uPSlate
…・・…‥・:downstale(rcsLo】一Cd)Fig.2 AlleXaml)1eofasystcmfailul・eilluSe.
:uPSlale ・…・・・…・ :downslalc(l・eS10l・ed)Fig.3 Anexampleofasystemfailureunderrestora−
tion. dcmall〔loccurswhenthesystelnisl・eStOl・Cd,Pl・OVidednfaultshavealrea(lybeellCOrl・eCted.al・eglVelll)V
tiol’1aCtionis perbrme〔1at timepoillt t(see Fig.3),
andgivenby
ガ「(り≡Pl・(ズ<Tl.lズ(f)∈兄) (8)=差篭㌘/差捌)・
Referellces
回D.P.Gavel・,Jr.,“Al)1・Obabilityproblemarisi11g
illl・elin・bilityn・11(ltl・afhcstu〔1ics,”Opel・atiollS Rc− Sen・1・(九vol.12,1)1).534−542,1964. 【2】S・Os几1くi,“Rclinl)i】ityarlnlysisofn・SySt(一11−WllCll itis us(,(lilltel・l11ittclltly,”(illJfl・1)illlCSC)rnn・11S.IECE,VOl.54−C,11O.1,1)1).83−−89,.Jn丑1071.
回K・1t)1くl−110 n・1■1(lS・Yn・1−−a(■h一、“Usel・−01・iellt(−(1 SOftwalLCl●eliil・bility assesslllCllt t(d’1110logy,”(ill17nl)n・11(一He)Bu11(!til10ftlll()t7呵)nnSo(:ietyhl・Ill(lus−
tl・ii11Al)1)1ie(トⅣhtll(−111n・ti(:S,VOl.10、11().3,1)1).186−− 197,S(!1)t.2()()().
Acknowledglnellts
Tlliswol・kwilSS11l)1)OrtC(1illl)il・1・tl)yil・Gl・n111t−ill−Ai(1 tbr S(:ielltih(:Rcsetu・(:11fl・01’11the Millistry of E(luczlr−
tioll,ScicllCe,n11(lC111tl11・(1()fJal)a・11ull(l(u・Gl・a・11t.No.
12G80442.
入nり+入′l.’
β 〝+/ノ・n一’ Pl・(ZT,.<y)= Pl・(ズ<了1−1†= 1・eSl)e(:tivcly. LetZL,bctheralldoITIVn・l・iablcrcl)rCSCntillgthcsoft− WarCfailul・C−OC(二url・ell(二etil11ell’1eaSul・e(1fl・Omn・rbitra・rytimepoil止t・The disappointment probabilityin
useis(1cfinc(1nS tlle(:011(Jitiolla・11)1・OI)aI)ility tlrlttt n・ SOftwal・(一fと、ilurc()(二川1・s(lurlllgn・しISと一・g(一1)el・io(1,1)1・Ovi〔ト edthesystclllisllSC(la・ttil11Cl)()illtt(sc(一Fig.2),ful(l gl、′elll、))′ 吼(f)≡Pl,(ZJ.<1′lズ(り∈U)
/
芦人け月.′..(り
君′‖(り.(7)
‖=lI=∑
∩.=() 一り+入n nlltll(10tll(11・11il・11(l,1ctソ1L)(1tll(11・n.11(1()1111′nl・iil.1Jl(† r(一1)1・CS(一11ting tllC r(一StOl・flti()11tilrlClllCaSul・e(1fl・0111aトbihln・1・y tilrl(1l)Oillt t.The disappointment prob−
ability under restorationis(lcfillC(1ElSlニ11(・!(:Oll(1i−ti()11illl)r()bil・l)ilitytllntn・HSage(Iellliul(loc(:1】rSl)CR)rC
fl・l●(!titO川・tiolla(:tio11iscollll)l(血,1)l・OVi(1(一(ltll(一l・eStOl・n一