OBJECT-ORIENTED DEVELOPHENT by Donald G. Firesmith Software Hethodologiet Hagnavox Electronic Syeteme Company Advanced Software Syetems Division 1313 Production Road Fort Uayne. IN 46808 ( 2 1 9 ) 429-4327
WHY IS OBJECT-ORIENTED DEVELOPMENT (OOD) IMPORTANT?
1)
O O D ie one of the extremely feu eoftuare development methode actually deeigned for modern Ada ( * I language. real-time. embedded appllcatione. O O D is a eigniflcant improvement over more traditional functional decomposition and modeling methode in that OOD: a) b) c) d) e)
2)
Better managee the eize. complexity. and concurrancy of today’s syeteme. Better addreeeee important eottuare engineering princlplee euch a s abetract data types. levele of abstractionr and information hiding. Producee a better deelgn that more closely matchee real i ty. Producee more maintainable eoftuare by better localizing data end thue limiting the impact of requlremente changes. Specifically exploite the pouer of Ada.
VHAT IS OOD?
O O D ie a eyetematic. etep-by-etep eoftuere development method that: a) b)
c) d)
e) f )
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Hae an optimal domain of application the development of modern Ada appllcatione (e.~.. real-time. embedded eoftuare). Covere a l l e or a m a j o r portion. of the eoftuare life-cycle. Supporte exteneive parallel development. Henagee the complexity of large development efforte. le supported by detailed etandarde and proceduree. Requtree training and eupport to be effective.
O O D ie: a) b)
a
( i t )
Obj ec t-or i ented.
Ada-oriented.
Ada ie a regietered trademark of t h e U . S .
D.4.1.1
Government
(AJPO).
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c)
d) e) f )
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Based upon modern aoftuaro engineering. Recursive. globally top-down, hierarchical COHPOSITION method. Revolutionary in approach. A "grab and go" method. Relatively eaey to learn. Being aucceeefully used by several companlee. Still evolving (Bee figure 1 ) .
ABSTRACT DATA TYPES L ( s k o v , G u t t o g , Show (1970's)
INFORMATION H I D I N G (19721
Parnas
r
FORMAL TECHNIOUES R o b t n s o n , L e o v l t t (19771
NOUNS AND VERBS A b b o t t (19811
1
AFATDS EXPERIENCE M o g n a v o x (1985) OBJECT-ORIENTED DEVELOPMENT Ftresmtth,
et.
al.
(1985)
Figure 1 : The evolution of O O D D.4.1.2
OOD ia NOT: A functional, hierarchical DECOHPOSlTlOW A modeling method. Easily mated with much methode. Effective without adequate training. Conetrained to the claaeical muaterfall" Consietent with DOD-STD-2167 and related Standardized acroer the indumtry. Yet adequately eupported by commercially tools.
3)
method.
lifecycle. pre-Ada etandarde. available eoftWare
OOD IS OBJECT-ORIENTED.
An OBJECT ie an entity that: a) b)
.
Hae a value (e.g. data) or state (e.g. Suffere and/or caueee operatione.
Ada taek).
OOD producee: a) b) c)
Ada objecte that correepond to objecte in the real world. Ada typee (i.e.. object templatee). Operatione that operate on theme objecte.
O O D emphaeizee the implementation of objecte in terme of ABSTRACT DATA TYPES. O O D groupe. in the eame Ada package: a) b)
A mingle type and
A l l operatione that operate upon euch objecte.
O O D producee a eubetantially different eoftuare architecture than traditional functional decompoeition method8 euch am Structured Deeign which generate untts. each of which implements eome FUNCTION of the requirement8 epecification. 4)
OOD IS ADA-ORIENTED. Ada ie an object-oriented high-level
language.
Packagee. which are the main building blocke of properly designed Ada eoftuare. are ale0 the main building blockm produced b y O O D . The physical design produced by OOD ie top-down in terme of Ada: a) b)
Neeting and Context (i.e..
the Ada "uith" etatement).
OOD eeparately develope Ada epecificatione and bodies. O O D * e low-level teeting naturally accounte for Ada compilation order conetra 1 nte.
D.4.1.3
OOD Diaqrame clearly identify the vmrious Ada programming iinite. Ad8 PDL ir an intogral part o f OOD'r dorign 8nd coding rtopeThe Object8 produced by OOD aro implemented in Ada ae:
a) b) 0 )
Constants and variables Abetract data typor Taskr
The operatione producmd by OOD mro implemented a) b) 5)
iri
Ada primarily
Subprograms Taek entries
OOD IS BASED UPON HODERN SOFTVARE ENGINEERING.
OOD specifically addresses each o f the following eoftuare engineering principlee or concepts: a) b) c) d) e) f1
O O D IS RECURSIVE, GLOBALLY TOP-DOVN, HIERARCHIAL COHPOSITION METHOD.
Traditional software development methods are reetricted to the claeeic wuaterfall* life-cycle (eee Figure 2 ) in which: a)
The eoftuare requiremente are analyzed firet.
b) c) d)
The preliminary deeign ie developed eecond.
The detailed deeign followe. A n d eo on.
csc I lESlIffi
Figure 2: The claeeic "uaterfall" life-cycle D.4.1.4
1
Bocauoe tho eoftw8ro 1.
dmvoloped in 8 top-down manner only within the boundrier of 08oh lif~-cycIm phmre, theme aethode are at beet only locally top-down.
OOD .1 a r o c u r r l v e ~ globrlly top-doun. hierarchial compoeition method. Itr roftumre lifo-cyclm (om. Figure 3) diftors eignificantlY from the cl8eeio “uaterfalla life-cycle becauee r t le baeed upon reCUr0iOn and tWO concepte unique to OOD: tha Booth and SubbOOCh. A BOOCH is t h e collection of a11 eottuare reeulting from the recursive application of O O D to o mpecific met of coherent eottuare requiresente roquirernnte that rpecify a mingle well-defined problem.
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A SUBBOOCH ie a emall. onnagable eubset of a booch that ie identilied and developed during a eingle recureion of OOD.
See Figure 4. Note that theme two concepte have no obvioue natural relationehip to the DoD hierarchical decompoeition entitiee CSCI. TLCSC. and LLCSC. Beginning with the higheet abetraction level and progreeeing steadily dounuarde in terme of nesting and *uithingw. the booch le deeignedr coded. and tested in incremente of a eubbooch. Thug. the eoftwere groue top-down. eubbooch by eubbooch. via the recureive application of ODD until the entire softuare tree ie completed. Locally. however. OOD employe the appropriate technique (top-down or bottom-up) depending upon the epecific requirement8 of each individual development activity. This alloue very significant parallel development baoed upon the “Deeign a little. code a little. teat a little“ concept. 7 )
AESPONS I B I L I T I ES. The f o l l o u i n g pereonnel have OOD reeponeiblitiee ( e e e F i g u r e 5 ) :
a) b)
Hanagement Softuare Development Teams. each coneistino of a: - Designer - Programmer Teeter Hetrice Collectore Softuare Puality Evaluation Softuare Syetem Engineering
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c )
d) e)
8)
SUBBOOCH DEVELOPHENT
The eubbooche that compriee each booch are recureively developed in a globally top-down fashion. The development of each eubbooch coneiete of the following three EUbph86ee: D.4.1.5
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0B.ECTOAIENTED DEVELOPrENT BUILD L
1
WTWARE
INTEGRATION
AN0 TEST BUILD L
1
SYSTEM
INTEiFAlIm AND TEST BUILD L
0
Figure 3: Tho O O D eoftuare life-cycle D.4.1.6
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I
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I I
I I
I I
I
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TERTIARY SUBBOOCH RESULTING FROM THE USE OF RECURSION
WHEREI
0
R E P R E K N T S A SUBPWXRAM A N 0
REPRESENTS A PACKAGE
I
REPRESENTS A MPENDENCY
Figure 4: Sample Booch structure D.4.1.7
H I Softwmrm I I G I Dmv. Tmmm I I
Objmot-Orlmntmd Dmvmlopmmnt Proammm -
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g
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o
~
~
g
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g
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n
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I----------g ~ ~
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I s I H I Q ~
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o
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g
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Tit 10 I T l D l P l T l C l E = = = = = = = = = = ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 1 I INITIATION OF BOOCH DEVELOPXENT 1 1 1 I l l 1 4 Step
I SUBBOOCH REQUIREHENTS SUBPHASE I Inltimtlon of Subboooh Dmvmlopmmnt I Inltimtlon of tho SDF I Problmm Statmmont I Rrpuirmmsntm Analymim I Subbooch Roquirmmmntm lnmpmction
Hanagement D = Deeigner(e) P = Programmer(e) T = Teeter(e) NC = Hetrice Collector(0) SPE = Software Puelity Evaluation
HGHT
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4
1 4 1 4
1
1 Primmrv or major rmmponolbility 2 = SrOond8ry rrrponmibility 3 m tlanageriml reeponeibility 4 = Indmpmndmnt mudit responeibility
FIGURE 5: OOD Reeponeibilitiee
D.4.1.8
‘m
a) b) a)
Subboooh Rmquirmmmntm. Subbooah Dmmigtz. Subbooah Cod. and Tmmt.
Thm SUBBOOCH REOUIREHENTS SUBPHASE h8m tho following rtope:
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INITIATION OF SUBBOOCH DEVELOPHENT Tho Hmnager initimtoe mubboooh dmvolopmmnt by idmntifying the mombere of the 8eSOt~iated Softw8rm Devolopment Toam and t8mking them to meet an 8mrigned oahmdulm 0 2 mubbooch milmstonee.
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INITIATION OF SOFTWARE DEVELOPHENT FILE (SDF) The Deeigner initfatom t h m aeoooiatmd SDF by obtmining an ompty SDF binder 8nd inmorting tho initial Soitw8re Engineering Form. ( S E F S ) that make up the covmrp8ges.
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Tho Softuoro Dovolopmont Te8m jointly PROBLER STATEHENT atate in a eingle eentrnce the problam to be eolved during the current recureion.
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The Softuare Development Team jointly REQUIRERENTS ANALYSIS col lect. analyze. clari iy. organize. and identify the eubbooch requi rrmente.
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SUBBOOCH REQUlRE?fENTS INSPECTION The Deeigner prepares the SDF f o r inepoction. Tho Hanager echeduleo the apreocioted meeting. The Hanager. the Programmer* and the Teeter perform the inepection. The Software Development Team takee any 8ppropriate corrective action. The SUBBOOCH DESIGN SUBPHASE has the following mtepe:
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The Software Development Team (under the LOGICAL DESIGN leaderehip of the Deeigner) devralope in a eingle paragraph a logical design that properly eolvoe the problmm of t h e current recureion and identifiee the relevant object6 and operatione. OBJECT ANALYSIS - The Software Development Team (under the leadarehip of the Deetgner) anrlyzee a11 relevant ObjeCte in the logical deeign perrgrrph. determinee and documente their relevancy. and providee the relevant objecte uith valid Ada identifiere- brief deecriptione, and a liet ot aeeociated ottributee.
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The Software Development Team (under the OPERATION ANALYSIS leaderehip of the Doeigner) 8nmlyzeo all relevant operatione in the logical deeign paragraph. determines and documente their relevancy* and providee the rrlevent operatione uith valid Ada identifiers. brief dercriptiono. and a liet of aeeociated at t r i butee.
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HODULE IDENTIFICATION. ORGANIZATION. AND DEPENDENCIES The Software Development Team (under the leaderehip of the Deeigner) organizee all relevant objecte and operatione D.4.1.9
by typm8r idontifimm thm non-nmmtmd unitm f o r maoh muoh Or98niz8tionr n m m t m thm orgmniamd objmctm and OpmratiOnm within thmro unitr. 8nd dmtmrminom tho vimiblo dmpmndmnoimo bmtuoen thmmo unitm.
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SUBBOOCH PRELIHINARY DESIGN INSPECTION Thm Dmmignmr prmparmm Thm P r o g r m m m m r and Tmrtmr pmrform the SDF f o r inmpmotion. Thm Softuarm Dmvmlopmmnt Imam takmm m y thm Inmpmotion. approprimtm oorrmotivm action.
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DESIGN ANALYSIS Tho Softuarm Dmvmlopment T m 8 m (undmr thm lmadmrmhip o f thm Dmsignmr) a n a l y ~ o etho dmmignr idmntifiom the typm of thm nemtmd unitm. oommon m o f t u a r m * and nertmd unite requiring rmureion. mto.
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CODING OF UNIT SPECIFICATIONS The Softwaro Development Te8m tundor tho 1madarsl.ip of the Demignor) implmmmntm and bottom-up manner in t e r m m of unit dmpondenciomt compiler. in Thim includmm the the Ada epeoiticatione of all unite. development of epecification hmadere. PDL. commantm. and code f r o m ekoleton unit epooificatione.
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SUBBOOCH DETAILED DESIGN INSPECTiON The Derigner prepmrem the SDF for inepmction. The tlotriar Collootor colleotm. eummarizee. and reportm the eubbooch design motrice. The Programmer end Teeter perform t h m Inmpmction. Thm Softuere Development Team takes any rppropri8tm oorrrctivm action. The SUBBOOCH CODE AND TEST SUBPHASE ham the following stepe:
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CODING O F U N I T BODIES The Software Development Team (under the leaderehip of the Programmer) implement. and compilom* in a top-down manner in terme of unit dependenciem. t h m Ada bodiem of all unite to be implementod during thm currmnt build. Thio tncludee the development of body h e m d e r m ~ PDL. cornmente. and code from ekeleton unit bodiee ueing the technique ot etep-uiee retinement.
S U B B O O C H TEST PLAN - The Software Development Team (under the leaderehip o f the Teeter) develope the teet plan b y determining. creating file0 of. and documenting the tset input and expected teet output date required f o r all aubbooch teeting end documenting the allocetion of theme teat camem to specific eubbooch teeto.
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S U B B O O C H TEST SOFTVARE The Software Development Team (under the leadership of the Teeter) demignm. implemrnts. rnd cornpilee all teet eOftWare program8 required f o r subbooch teeting echeduled for the, current build. S I J B B O O C H TEST PROCEDURES
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The Softuare Development Team (under the leaderehip of the Teeter) develope the detailed s t m p - b y etep proceduree f o r performing 011 eubboooh tmmtr moheduled Zor the current bui Id. D.4.1.10
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SUBBOOCH CODE INSPECTION Tho Progrmmmer proparen tho SDF for inrpootion. T h o Hotrior Colloator o o l l o o t m l m u m m a r i z o m ~ mnd rmportr tho rubboooh o o d o motriam. T h o Softuaro Dovmlopmont Trmm porform tho inmpootion. Thm S o f t u a r e Devolopmont Tomm tmkor mny approprieto corrootive action.
INITIAL SUBBOOCH TESTING
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The Softuarm Development Team (undor tho l o m d e r ~ h i pof tho T o ~ t o r )perform and document tho rorultr o f a11 initial rubboooh torte.
9)
PRACTICAL EXPERIENCE. T h e uee of O O D at Hognavox on the AFATDS Project (over 50K linea of Ada c o d e eo f e r ) hee rmsultad in the follouinQ leoeone 1 earned : Avoid overe:mcrfying the requirementfa uith cexplicit o r implicit deeign information of a functional decompoeltion nature. I f e functional decompoeition method ie ueed to produce the top-level deeign. I t uill be incompatible uith the deelgn produced by O O D at the lower-levele and numeroum interface problem6 wi 1 1 roeul t.
Replacing the previoue functional decompoeition mindeet isa difficult. primarily among the more experienced deeignere. T h e concept o f
recureion re fairly difficult to meeter.
O O D training and eupport in t1.e method need.e to continue beyond the c 1 aeeroom. 000 n e e d s to be further refined. primarily in the area of
teet traininn le a s necemsary ae training d e e i g n mntl programming.
in A d a - o r i e n t e d
O O D improves deeigne due to:
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Proper abetraction levele. Proper information hiding. High modularity. Improved interfacee. Good eupport f o r etrong typing. Good correepondonce to the, real uorld.
O O D improvee productivity d u e to:
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Fnhanced parnllel development. Reliee of code. Eaey coding f r o m deeigri intormation. Eoey modification Of deeion and code.
D . 4 . 1. 1 1
object-oriented develophent
Hagnavox Electronic Syeteme Company. Advanced Software Syetems .... Traditional software development methods are reetricted to the claeeic wuaterfall* ...
