PAlI PUBLIC ANSWERS TO EXERCISES Chapter 4. Developing requirements E4. 1 p 106 Listing information to be consulted when performing a domain analysis a)*Police information system Police officers and staff (interviews, brainstorming and observing work) Police training and procedures manuals Documentation of existing software and equipment used by the police (including competing products) Books about police methods Similar information about related activities such as court procedures, etc E4. 2 P. 106 Writing a short domain analysis for a system We will not be providing any answers to this exercise since the answers will depend too much on the information consulted, the country in which the reader resides, and the date the infomation is gathered E4.3 P 110 Defining and narrowing the scope of a system In this following answers, a reasonably complete set of possible system functions is listed. The functions in bold are the ones that represent the minimal requirements of a first release. Of course, each persons answer will be somewhat different; however, the sample answers suggest the scope of good answers to this question (See E9. 1 for additional exercises based on these systems) a)*Police information system Managing personnel information about officers and staff (note that a generic personnel management system could also be used to do this, although it would have to be hooked to the police system to enable some of the other functions mentioned below) Managing basic information about areas and events to be patrolled Facilitating the manual scheduling of the duties of officers and staff Automatically proposing schedules for some of the duties of officers and staff Managing basic information about each case being investigated Managing the documents that have to be written regarding each case, and following each shift Generating statistics and trend information about crime rates etc Managing detailed information about suspects, witnesses and other people relevant to cases Providing links to drivers licenses and other databases to help police find infomation Providing links to court and criminal records E4.4 P. 110 Giving precise problem statements, considering high-level goals a)*The new police information system will make operations of the police department more efficient by reducing the time and effort required to plan and execute work, as well the time required to enter and find information required in routine police work E4.5 p. 115 Describing functional requirements of a system These build on the answers to E4.3 and E4.4 above a)* Police information system To be provided in a later version of this document E4.6 p. 118 Classifying requirements into fimctional or non-functional. a)*F. Describes the computation to be performed( some security requirements are non-functional, but this one seems to be in the functional category) c)"NF. Constrains response time E4.7 p. 118 Rewriting requirements so they are verifiable In each part of this questions, we would expect an answer similar to one of the bulleted points. Some of the bulleted points show that there should be two or more separate requirements a)*Constraint on technology to be used The C++ programming language must be use A strongly typed, block-structured programming language must be used that does not allow unrestricted C 2002 TIMOTHY C. LETHBRIDGE AND ROBERT LAGANIERE
PA11 PUBLI C A NSW ERS T O EX E RCISE S © 2002 T IMO TH Y C. LE T HBRI D GEA N D RO BERT L AG AN I ÈRE Chapt er 4. Devel oping r equir em ent s E 4.1 p. 106 Listing inform ation to be consulte d whe n pe rform ing a domain analy sis. a )*P olic einf orm at ion syst em • Polic eoff ice rs and sta ff(inte rvie w s, br ainstor ming and obse rving w or k) • Polic etra ining and proce dur es ma nua ls • D oc ume nta tion of e xisting sof tw ar ea nd equipme nt used by the polic e ( including compe ting pr oducts) • Books about policeme thods • Simila r inf or ma tion a bout re la ted a c tivitie s suc h a s court pr oc edure s, etc. E 4.2 p. 106 W riting a short dom ain analy sis for a syste m . W e will not be providing a ny a nsw er s to this e xe rc ise sinc e the a nsw er s w ill depe nd too muc h on the inf or mation c onsulte d, thec ountr y in which the re a de r r eside s, a nd thedatetheinfor ma tion is ga the re d. E 4.3 p.110 De fining and narrowing the sc opeof a sy stem . I n this following answe rs, a r e asona bly c omple te se t of possible syste m f unc tions is liste d. The f unc tions in bold a re the one s tha t re pre se nt the minima l r equir ements of a fir st r e le ase . Of cour se, e a ch pe rson’ s answe r w ill be somew ha t dif f er ent; how ever , the sa mple answe rs sugge st the sc opeof good a nsw er s to this que stion. ( Se e E 9.1 f ora dditiona l e xe rc ise s based on these syste ms) a )*Polic einf ormation system • Managing pe rsonnel informa tion about off ice rs and sta ff (note tha t a generic pe rsonnel ma na gement syste m c ould also beused to do this, although it w ould ha veto behooked to thepolic e syste m to ena ble some of the othe r functions me ntione d be low ). • M anaging basic inf or m at ion about ar e as and eve nt s t o bepatr olled • F ac ilitating them anual sc he duling of thedut ies ofoff ice rs and staff • A utoma tica lly pr oposing sc he dules f or some of the duties ofof fice r s and sta f f • M anaging basic inf or m at ion about eac h case be ing inve st igate d • M anaging t he doc um ent s that have to bew r it te n r egarding e ac h c ase , and f ollow ing e ac h shif t • G ener a ting statistic s a nd tr end inf ormation a bout c rimera te s etc. • Managing de ta ile d inf or ma tion a bout suspe cts, witne sses and otherpe ople re levant to c ases • Providing links to dr iver s lic e nses and otherda ta bases to he lp policefind infor ma tion • Providing links to c our t a nd c r imina l re c or ds E 4.4 p. 110 G iv ing prec iseproble m state m ents, c onsidering high-le ve l goals. a )*T he ne w polic e inf orm at ion syst em will ma ke oper a tions of the police de pa r tment mor e e ff icient by r educ ing the time and e ff ort r e quir e d to plan and e xe cute wor k, a s w ell the time re quire d to entera nd find inf or mation r equir ed in r outinepolicew ork. E 4.5 p. 115 D esc ribing functional re quire me nts of a system . T he sebuild on thea nsw er s to E 4.3 a nd E 4.4 a bove. a )*Polic einf ormation system T o bepr ovide d in a laterve rsion ofthis doc ume nt E 4.6 p. 118 Classify ing re quire me nts into func tional or non- functional. a )*F. D escr ibe s thec omputa tion to beper f or me d ( some se c ur ity r equir eme nts a renon- functional, but this onese ems to bein the functional c a te gor y) c )*N F. Constr ains re sponse time. E 4.7 p. 118 R ewriting requirem e nts so the y arev erifiable. I n ea c h pa r t of this questions, w e w ould expe c t an answ e r similar to one of the bulle ted points. Some of the bulle ted points showthat ther eshould betwo ormorese pa ra te re quire ments. a )*Constr aint on te chnology to beused: • T heC+ + pr ogr amming langua gemust be use d • Astr ongly type d, block-structure d progr a mming langua gemust be used that does not allowunre str ic te d a cc ess to memor y
PUBLIC ANSWERS TO EXERCISES PAI2 c)* Constraint on availability and throughput The system will accept connections 24 hours a day, every day, with a maximum downtime of 5 minutes a month, which can occur only between 12: 30 a.m. and 1: 30 a.m. North American Eastern Time When available, the system will at all times be able to manage 200 simultaneous connections, and process 2000 transactions per minute E4.8 No public answer E4.9 p. 119 Writing non-functional requirements These build on the answers to f4..5 abov a)*Police information system When the user is connected to the over a local area network, the system shall respond with complete responses to all inputs within 0. 5s at peak system load When the user is connected over a wireless connection at 9600bps, the system shall respond with omplete responses to all inputs within 3s at peak system load The system shall be capable of handling 50 simultaneously connected users, and 300 user interactions (events originating from users)per minute The system shall not consume more than 200MB of RAM while running at peak capacity The system shall not consume more than 56Kbps of bandwidth per connected user(averaged over any Is tir The system shall achieve a reliability level of no more than 1 failure per 10 user hours, with none of those failures rendering the system totally inoperable The system shall be available 99.9% of the time with no period of down time exceeding 2 minutes The system shall be designed so that large numbers of additional functions can be added with little The system shall be designed so that it could be adapted to the needs of other police departments with programming The server shall be able to run on a Windows 2000(or higher)equipped system, with a 1. 4 GHz or faster Intel processor, 300MB or more of RAM, and 15GB or more of disk space The client software shall be able to run on EMP-4500 police car terminals, as well as on EMP-4500 emulators running on desktop computers E4.10 P. 122 Practising interview techniques This is a purely practical exercise E4. 11 P. 124 Practising brainstorming techniques This is a purely practical exercise E4. 12 No public answer E4. 13 No public answer E4. 14 No public answer E4.15 pp 129-130 Describing the type of requirements document needed. a)" Software controlling a manned spacecraft sent to Mars There would need to be a considerable amount of detailed technical requirements documentation Technical terminology could be used since all readers would be expected to have a technical background. There would probably initially be a very high-level description of the missions overall objectives used to obtain funding for the mission. Then there would be a requirements document for the high-level system requirements of the combined hardware-software system. Next, the system would be allocated into hardware and software subsystems, which in turn would each be divided into several subsystems. At each level there would probably be general and detailed requirements documents. The rationale for this level of detail is that a spacecraft is novel, is technically complex, will involve many different people with different types of expertise to develop, is difficult or impossible to change once launched, and is expensive(with high failure cost and hence a high level of required reliability ) THESE ANSWERS SUPPORT THE BOOK OBJECT ORIENTED SOFTWARE ENGINEERING
PUBLI C A NSW ERS T O EX E RCISE S PA12 T HE SEAN SW E RS SU PPORTT HEBO OK O BJ ECT O RI E NTEDSO FTW AR E E NG INE ER ING : c )*Constr aint on a vaila bility a nd throughput • - T he system will ac ce pt conne ctions 24 hours a da y, ever y day, w ith a ma ximum dow ntime of 5 minute s a month, w hic h ca n occ ur only be twe en 12:30 a .m. a nd 1:30 a.m. North A me r ic an Ea ste rn T ime. - W he n a va ila ble, the syste m w ill a t a ll times be a ble to mana ge 200 simulta neous conne ctions, a nd proce ss 2000 tr a nsac tions pe r minute . E 4.8 No public answe r. E 4.9 p. 119 W riting non-func tional requirem ents. T he sebuild on thea nsw er s to E 4.3 -E 4.5 a bove. a )*Polic einf ormation system • W he n the user is c onnec te d to the over a loca l a re a netw or k, the syste m sha ll re spond with complete r esponse s to all inputs w ithin 0.5s at pe ak system load. • W he n the user is c onnec te d ove r a w ire le ss conne ction a t 9600bps, the syste m sha ll re spond with c omple ter e sponses to a ll inputs within 3s at pe ak syste m loa d. • T he system shall be c apable of ha ndling 50 simulta neously c onnec te d use r s, a nd 300 use r inte ra ctions ( events or igina ting f rom use rs)perminute. • T hesystem shall not consumemorethan 200MB of RA M w hile running at pe ak c a pa city. • T hesystem shall not consume morethan 56Kbps of ba ndwidth pe r conne cte d use r (a ver age d ove r any 1s time pe r iod) • T he system shall a chieve a r eliability le ve l of no more than 1 fa ilure pe r 10 use r hours, w ith none of thosefa ilure s r ende r ing thesystem tota lly inoper a ble. • T hesystem shall be a va ila ble 99.9% ofthe time with no per iod of dow n time e xc ee ding 2 minute s. • T he system shall be designed so tha t lar ge numbe rs of a dditiona l f unctions c an be a dde d with little r eprogra mming. • T he system shall be designed so tha t it c ould be a dapte d to the ne eds of other police de pa rtments with minima l re progr a mming. • T he se rver shall be a ble to run on a W indow s 2000 ( or higher ) e quipped syste m, w ith a 1.4 G Hz or f aste rI nte l pr oce ssor, 300MB or mor e ofRA M, and 15G B or mor e ofdisk spac e . • T he c lie nt softw ar e sha ll be a ble to run on E MP-4500 police ca r ter minals, as w e ll a s on E MP-4500 e mula tor s r unning on de sktop c ompute rs. E 4.10 p. 122 P rac tising intervie w te c hniques. T his is a pur ely pra c tica l e xe r cise . E 4.11 p. 124 P rac tising brainstorm ing tec hnique s. T his is a pur ely pra c tica l e xe r cise . E 4.12 No public answe r E 4.13 No public answe r E 4.14 No public answe r E 4.15 pp. 129- 130 D esc ribing thetypeof requirem ents doc um ent nee ded. a )*Sof tw arec ont rolling a manne d space c raftse ntto M ars • T he re would nee d to be a c onsider able amount of de taile d tec hnica l r equir eme nts doc ume ntation. T ec hnica l ter minology c ould be used sinc e a ll re ade rs w ould be expec te d to have a tec hnica l bac kgr ound. T he re would probably initially be a ve ry high- le ve l desc ription of the mission’s over a ll objec tives used to obta in funding f or themission. Then ther ew ould bea re quire ments document f orthe high- level syste m re quire ments ofthe combine d har dwa re - softw ar e syste m. Ne xt, the syste m w ould be a lloc a te d into har dw a re a nd sof tw ar e subsyste ms, w hic h in tur n would e a ch be divide d into sever a l subsyste ms. A t e ac h level ther e w ould pr oba bly be gener a l and deta iled re quire me nts docume nts. T he r ationale f or this le ve l of de tail is tha t a spa ce c ra ft is nove l, is te chnic ally complex, w ill involve ma ny dif fe r ent people w ith dif f er ent type s of expe r tise to de ve lop, is diff icult or impossible to cha nge onc e launc hed, a nd is e xpe nsive( with high fa ilurecost and hencea high le vel ofr equir ed re lia bility)