November/December 1991 Vol. 4, No, 7 Editorial 6 Features Guest Editorial 8 Boti Magnmson 10 Contravariance for the rest of us byWarren Hati c++ 40 Gntravtimce is a phenomenonthat occurs as an interactionbetweensubtypingartdhigher- Understanding constructor initializers order fincriona. II affecu allobject-orientedprogramminglanguagesincludingC++ and is usually in C++ circumven~cdby overlodlng. The author providesmamplesin C++ whereoverloadingdoa not Andrm Koenig havethe desiredeffect,and discusseswhat a be,ter — more expressiveand ~esafe — language might look like. Modeling & Design 48 The evolution of bugs and systems Jamer Rumbaugh 19 Multilevel secure object-oriented data model — issues on noncomposite objects, composite Tools 53 Making inferences about objects objects, and versioning Pard Harmon by Bhavani Thurukingham ~Ile progress mukilevel securi~ Smalltalk 56 hm beenmade in incorporating into an object-rientcd data Combining modal and nonmodal mndel,,mrr& stillremainsto be done. This articlediscussesthe issuesinvolvedin supporting components to build a picture viewer noncomptrsiteartdcompsite objectsand versioning,which havenot yet been investigated in such W~LaLon& &John Pugh models,becausethesefraruresare exential for data-intensiveapplicationsin hypermediasystems, CAD/CAM, and knowledge-baaedsystems. Book Review 64 Eiffe/, the Language Rmiewed by Stm.n C. Bihw 31 Delegation in C++ byRa~bJohnson &Jouthun M. Zwe& Advertiser Index 66 Delegationis ofren viewedas a languagefealurethat replam inheritance,when in fact ir cart be viewedasa relationshipbetweenobjeccsrhat can be implementedin any object-orientedlanguage. This articleofirs an exampleof this mefuJprogrammingtechniqueusingC++. Career Opportunities 72 & Training Services 35 Real-world reuse byMark brenz Much of the f?crraof object-oriented(O-O) developmenttodayis on rheclaashierarchyand reuse through inheritance.In reality,most of dte classmin an applicationare drawnfrom variousposi- tions in the hierarchyand work together through collaboration.Th]s author dlscusscsO-O analpis and designmedtndologiesand CCICIISchathe believeswillcome inlo wideruseasapplicationdevel- opers foc~ more on thismllabo~[ion and l~s on the hie~rchy. The Journal of Ohjecr-OrientedProgramming(lSSN #OS96-E1438)ispubli.rhedninerimesa year, monthlyexceptfor k4ar/Apr,Jd/Aug, andNov/Dec. Publishedby SIGSPuhlica- riotr.r,Inc., 586 Broadway,Suire604, NewYork, NewYork 10012, (212)274-0640. Pleasedirectadvertisinginquiriest. thisadd~. Secondclasspnsragepaidat NewYork, New York, and additionalmailingoffiw. POSTMASTER: Sendaddreaschangesm JOOP, P.O. Box 3000, Dept. 00P, DenviUe,NJ 07834. Inquirimand newsubscriptionorders &odd dso be sem 10 rfraraddress. @ Copyright 1991 SIGSPublications,Inc. Allrightsresewed.Wpmduction of rhismaterialby electronictmsmiwion, Xerox, or any other merhodwiUbe rrearedasa willhl viola- tionof the US Copyright law and isSarlyprolribired.Materialmaybe reproducedwidrexpressPermision km rhepublisher. Manuscriptsunderreviewshouldbe ~pcd doublespad (in triplicate).Ultorial correspondenceand ProductNw informationshouldbesentto the Editor, Dr. RichardS. Wiener, 2185 Bmadrrtoorhad Clrde, Colorado Sprin&,CO 60906, (719)520-1356. 5 EDITOR Dr. Rich.ardWIcner :..:,. Editorial UniuerriIyofCOhra&,Cob& Spring ,:.,:,+’ SIGS PUBLICATIONS ,.:.:?...., EDITORIAL/ADWSORY BOARD M Them Aiwn4 Objti DcsiP Gndy Booth, RatioMl GWW hnh, Di@talk BradJ. b, Information Agc-&&ting Chuds M, Th Wbitcwatm &up Adete cald~ ParcPhc syrtcmI was t niceto meet with so many of our readen and writers at 00PSLA this past week R. Jo* Kreiidler, &ncrdEhm”c T (October 7–1 1). I found 00PSLA to be an interesting and important conference. Th9m h, Combnt ~ M-, ISE The technical papers at the Cctnkrence focused on experiences wi& object orientation. Mefi P~Joncs, WaykIndS_ 1 The industxy now has some real experiences, both successes and fillures. Some of - Prarap, &wLine .So~rr, Inc. P. Michael Seaahoh, Vemant Object Tech. the mote successful OOP book authors were on hand to discuss their recipes for O-O anal- Bjarne StrouamIp, AT&TBeflLabs ysis, design, and programming. Representatives from the entire 00P industry were pre- mm TSwuua, Object TccbnobgyInk-tnatiod sent. It was evident to me that the move toward making objecr orientation a mainstream JOOP ADVISORY BOARD activity is mntinuing. Of course, it is important to temper this observation by the fact Dtiel Fii, Hewkti-Packardbb. StuaK Gr-etd, Marirt College that whenever one is immersed in a sea of advocates of any technology it is easy to be- IvaIJawb.san, Objti”w Syrtcms lieve that tbe whole world has embraced the technolo~. In reality, this has not yet hap- Boti Magnusmn, Luwd Unim”ty, Swc&n k Phn, Unimi~ ofCohr& pened with object-oriented technology and may take several more years to occur. Many * Wq LfoMIntwtio.1 computer science departments are still teaching their students structured analysis, design, COLUMNISTS and programming techniques exclusively. Some schools have just started offering a few Geo~ Boworth, Dip”tah elective courses on object orientation. Nicliieben B.urbalii, Lucid Inc. Pauf Buttaworth, hi. LOB2 It was clear from the vendor area that most of the products exhibited featured C++ or Paul Harmon, Conridkznt Smalltalk language development or sobare development tools. These two 00P lan- Jon Wyatt Hopbim, Pahdio So@,r Andrew Wg, AT&TBelhb~ guages have “won” the Imguage wars in the commercial sector, at least for the time being. Wdf Wndc, CurferonUniwrriy Application frameworks and CASE tools hr C++ were probably the most popuk prod- John Pugh, G&ton Univw,ig jama Ruinbaugh,Gc~dE&& ucts on display.The -jor application areasthat are pushing 00P bol~ into the rrsain- Tonyw—, IDE strearrsare O-O database management and the development of graphical user interks. C. The- Wu, NaualPwtgr&te School E* Wiener, ProdtiNtws titer We at ]OOP wodd like to report on experienw with object orientation and there- fore plan to produce a special supplement dedicated to tils subject in 1992, I would SIGS PUBLICATIONS, lNC, Iii to solicit contributions now for this special supplement. PI= fo~ow the notrnalJOOP Richard P. Friedman guidelines for submission and mail your manuscripts to the editorial offi~. You are wel- Founder & tip Publisber come to call me at the editorial office to discuss ideas for such contributions, ART/PRODUCTION This issue contains four feature-length articles. Elk VatiaII, Managing Utur “Contravarianw for the R=t of Us” by Warren Harris discusses a structural weakness S- CulliganCreati.Da-ectOr Elii.h A.Upp,ti.-tion Editor of C++ related to overloading. The article suggests areas of needed improvement for b Poher, kktip Desipm c++. CIRCULATION “Multilevel Secure Object-Oriented Data Model: Issues on Noncomposite Objects, Diane Badway, Cin-nluion Burinm ManaIm Gmposite Objects, and Versioning” by Bhavani Thuraisingham examines the issues Iia& ti~ h~fimmt Manager JohnSchreiber,Circuhonhistant related to maintaining multilevel securi~ of data in an object-oriented environment, “Delegation in C++” by Ralph Johnson and Jonathan Zweig ex~ines delegation as MARKETING/!!VERTI SING James ~, Ad&incDircctor a language featme that replaces inheritanm. The titicle explores how delegation may be used in C++. “Real-World Reuse” by Mark hrenz looks at how application developers work with .- ADMINISTRATION and view their application classes and how this relates to analysis, design, and the hier- David h+ Acmunting S-e Wd Dinne&, GnfinccMa~ archy of classes used for an application. J-& FAeI, Arsi.rtanta tbrPublisbcr Laura h Tayfor, &intiwAr.iirtant [email protected] R Monck GmtralManaF I Richard S. Wiener Publishersof]oumalof Object-Oriented Programming Object Mafa>e, Hodim on Objcrt-Orirntcd hogram- ming Tbe C++ @ti, The SmaU R+ti, The Inti- ti”owl 00P DimctoV, and Tbt XJoumal 6 JOOP NOVEMBE~DECEMEiER 1991 z.,;.~,:..~.i;,... ,,:.:J ,., ~,,,.!..ii,.,.,...,..; ~., .-:::“....,.“..:;.:7,r:,. ,.., .,,........,.......... ., ,, . .. .. ,.. ... titi aWorld-ClassP&er . .. ,. Your KSC Guides 00 ANALYSIS Development Team ... to E~ctive a ) solutions ADVANCED TRAINING ~.‘- .. ,, .,.,., .,.. FRAMEWORKS . 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