Internatonal Journal of Scentfc & Engneerng Research Volume 2, Issue 7, July-20 An Integrated Approach of AHP-GP and Vsualzaton for Software Archtecture Optmzaton: A case-study for selecton of archtecture style K.Delh Babu, P.Govndaraulu, A.Ramamohana Reddy, A.N.Aruna Kumar Abstract Software Archtecture has emerged as an mportant sub-dscplne of software engneerng. A key aspect of the desgn of any software s ts archtecture styles,.e. components and connectors and ther relatonshps. Selectng the best style s dffcult because there are multple factors such as proect rsk, corporate goals, lmted avalablty of resources, etc. Therefore ths study presents a methodology for selecton of software archtecture styles. In ths paper we eplore the Analytc Herarchy Process (AHP) wthn a zero-one goal programmng (ZOGP) model for selecton of archtecture styles. AHP s appled to the decson problem nvolvng multple alternatves and crtera and ams at selectng an alternatve from a known set of alternatves. Then Goal programmng model s used to optmze the obectve functon whle smultaneously satsfyng all the constrants. Further, AHP-GP Vsualzaton framework and vsualzaton tool (SAVE Tool) are appled to evaluate the selected software archtecture style. Inde Terms Software Archtecture, Selecton of Software Archtecture Styles, Mult-Crtera Decson Makng, Analytc Herarchy Process (AHP), Zero-One Goal Programmng (ZOGP), Vsualzaton. INTRODUCTION N owadays, decson-makng has become more comple due to reasons related to () the alternatves, (2) the goals and (3) the envronment n whch decsons are beng made. Frst, for almost any decson the number of alternatves has grown dramatcally. Second, the number and the nature of the goals, crtera or constrants, have changed. When makng decsons, the goals are not lmted to related obectves. The thrd set of reasons for the ncreased complety of decsons refers to the envronment. The changng alternatves, goals, and envronment enlarge the complety of decsons and call for effectve decson support. The basc approach of mathematcal programmng models s to optmze the obectve functon whle smultaneously satsfyng all the constrants that lmt the actvtes of the decson maker. Software archtectures sgnfcantly mpact software proect success []. However, creatng archtectures s one of the most comple actvtes durng software development [2]. When creatng archtectures, archtecture styles narrow the soluton space: Frst, styles defne what elements can est n archtecture (e.g. components, connectors). Second, they defne rules on how to ntegrate these K.Delh Babu, Department of Computer Scence and Engneerng, Sr Vdyankethan Engg. College, Trupat, Andhra Pradesh, INDIA. Emal:kdb_babu@yahoo.com P.Govndaraulu, Department Computer Scence, S.V. Unversty, Trupat, Andhra Pradesh, INDIA. Emal: pgovndaraulu@yahoo.com A.Ramamohana Reddy, Department Computer Scence, S.V. Unversty, Trupat, Andhra Pradesh, INDIA. Emal: aramamohanareddy@yahoo.com A.N.Aruna Kumar, Department of Computer Scence and Engneerng, Sr Vdyankethan Engg. College, Trupat, Andhra Pradesh, INDIA. Emal: kolla_aruna@yahoo.com elements n the archtecture. Moreover, styles address functonal and non-functonal ssues [3]. Ths paper focuses on two mathematcal methods, Analytc Herarchy Process and Goal Programmng. Further, AHP-GP-Vsualzaton framework and Vsualzaton Tool (SAVE Tool) are appled to evaluate the selected software archtecture style. The contrbutons of ths paper are as follows:. Ths paper presents a methodology for selecton of software archtecture style whch uses two mathematcal technques Analytc Herarchy Process and Goal Programmng. 2. Analytc Herarchy Process (AHP) s used to determne the degree of relatve mportance among the alternatves and crtera. 3. It provdes a way of collectng epert group opnon along wth stakeholders nterests (e.g. relablty, performance) 4. Goal Programmng (GP) to determne the desred level of attanment for each goal and penalty weghts for over or under achevement of each goal [4] 5. AHP-GP Vsualzaton Framework and Vsualzaton Tool are used to evaluate the selected software archtecture style. In AHP, parwse comparsons matr s formulated and then the relatve prorty of each alternatve s calculated. After obtanng the overall prortes of alternatves and usng the goal constrants, zero-one goal programmng (ZOGP) model formulated. The combned use of the AHP and GP approaches etended the use of Mult Crtera Decson-Makng approach.
Internatonal Journal of Scentfc & Engneerng Research Volume 2, Issue 7, July-20 2 2 INTEGRATED APPROACH OF AHP-GP AND VISUALIZATION 2. Analytc Herarchy Process The ntal study dentfed the mult-crtera decson technque known as the Analytc Herarchy Process (AHP) to be the most approprate for solvng complcated problems. Decson-makng nvolvng multple obectves and/or crtera s called Mult Crtera Decson-Makng (MCDM) [5]. Often the crtera nclude both qualtatve and quanttatve factors, whereas the quanttatve crtera may be measured n ncomparable unts (for eample, the market share and the prce of a software package). T.L. Saaty ntroduced AHP to solve the problem of ndependence on alternatves and/or crtera. AHP allows better, easer and more effcent dentfcaton of selecton crtera, ther weghtng and analyss [6]. It reduces drastcally the decson cycle and allows organzaton to mnmze common mstakes by usng the epert group decson [7]. 2.2 Goal programmng After obtanng the overall prortes of alternatves usng AHP, wth these prortes and goal constrants, Goal Programmng (GP) model s formulated [9] as llustrated n fgure, step 5 to step 6. The GP model for archtecture style selecton can be stated as follows: Mnmze Z P ( w d, w d ) () Subect to a K d d b for =, 2,, m, =, 2,, n (2) d for = m+, m+2, m+n, =, 2,, n (3) = 0 or for (4) where m s the number of goals to be consdered n the model, n s the pool of archtecture styles from whch the optmal set wll be selected, = the AHP mathematcal weght on the =, 2,, n archtecture style, = some k prorty pre-emptve prorty, for =, 2,, m goals, = the th postve and negatve devaton varables for =, 2,, m goals, = a zero-one varable, where =, 2,, n possble proects to choose from and where =, then select the th archtecture style or when =0, then do not select the th archtecture style, = the th parameter of the th resources, and = the th avalable resource or lmtaton factors that must be consdered n the selecton decson. In Fgure, steps 5 to step 7 depct GP model. Fgure. Process Model for archtecture style selecton usng AHP-GP Vsualzaton Thus, AHP s a method of breakng down a comple, unstructured stuaton nto ts components parts; arrangng these parts, or udgments on the relatve mportance of each varable; and syntheszng the udgments to determne whch varables have the hghest prorty and should be acted upon to nfluence the outcome of the stuaton [8]. In Analytc Herarchy Process, a frst parwse comparson matr for alternatves and crtera are formulated and then the relatve prorty of each alternatve and crteron s calculated. In Fgure, step to step 4 depct AHP model. The presented GP formulaton can easly be rearranged or modfed dependng on the prortes of the decson makers and crcumstances of the decson envronment. The GP obectve functon ncludes the postve and negatve devatonal varables whch represent the devatons from the desred goal levels (.e., overachevement of a goal s represented by d+ and underachevement of a goal s shown as d-). Resource lmtatons are consdered more mportant. The soluton of the GP model wll mnmze the obectve functon and satsfy the goal constrants. 2.3 AHP-GP Vsualzaton Framework for Archtecture Style Selecton Vsualzaton s used to enhance nformaton understandng by reducng cogntve overload. The proposed AHP-GP Vsualzaton Model as shown n Fgure 2, overcome the lmtatons of the AHP-GP model as AHP-GP model address the non-functonal requrements of the software archtecture as desred by the stakeholder. The vsualzaton technques address the functonal key areas only.
Internatonal Journal of Scentfc & Engneerng Research Volume 2, Issue 7, July-20 3 The proposed model s the best model to choose archtecture style sutable for a gven applcaton as per both the functonal and non-functonal requrements [0] as n fgure, step 9. 3. Decson Herarchy Formulaton The decson herarchy formulaton s very mportant as the eport group agreed that the evaluaton crtera n the decson crtera are comprehensve and also agreed that the crtera should be epressed n farly general terms and should be understood by all stakeholders. They concerned both manageral and techncal factors were crtcal decson crtera. Based on the functonal and nonfunctonal requrements, stakeholders and eport group opnon and prevous proect nformaton are consdered to n the formulaton of decson herarchy [3]. Fgure 2. AHP-GP-Vsualzaton Framework for the selecton of archtecture style [0] 2.4 Evaluatng the Archtecture Style usng Vsualzaton Tool (SAVE Tool) Fraunhofer SAVE [] (Software Archtecture Vsualzaton and Evaluaton) s a tool for analyzng and optmzng the archtecture of mplemented software systems. Usng ths tool the functonal crtera as specfed n the AHP-GP-Vsualzaton Framework can be evaluated effectvely as depcted n fgure, step 0. Even from the source code, the archtecture styles used n the proect can be vsualzed and the functonal crtera can be evaluated. Also SAVE supports reverse engneerng, qualty assurance, and mantenance tasks for systems mplemented n Java, C/C++ and the etracted nformaton can be vsualzed, analyzed, manpulated or used to modfy system artfacts. 3 A CASE-STUDY FOR SELECTION OF SOFTWARE ARCHITECTURE STYLE A case study to llustrate the advantages of the ntegrated AHP-GP based on the epert opnon of an organzaton s taken. The problem conssted of prortzng three archtectures styles [2] on the bass of seven crtera deemed to be mportant for an organzaton. The crtera used are () Modfablty (M), (2) Scalablty (S), (3) Performance (P), (4) Cost (C), (5) Effort (E), (6) Portablty (Pr) and (7) Ease-of-use (Eu). However, we are of the opnon that there s an estence of relatve mportance among these seven crtera. The attrbute of crtera P nfluence crtera C, the attrbute of crtera E nfluence crtera Eu, S, Pt, C and so on. In order to check relatonshp of crtera or alternatve, we need to have group dscusson because the type of network or relatonshp depends on the stakeholders' udgment. Fgure 3. AHP-GP-Vsualzaton Decson Herarchy for the selecton of archtecture style 3.2. Parwse Comparsons Ths secton focuses on the comparson of the alternatves, wth respect to the other alternatves n the herarchy. The udgment of the mportance of one of the alternatve over the other can be made subectvely. The subectve udgment that s acheved can then be converted to a numercal value usng a satty scale of -9, where denotes equal mportance and 9 denotes the hghest degree of mportance. For ths par wse comparson, we follow bottom up method. In ths par wse comparson process, all the obtaned comparson results are evaluated by the epert group to better reflect ther percepton and understandng of the ssues. 3.3. Decson Weght calculaton Ths s the man step n the selecton procedure. Ths step focuses on gettng the nput from the Epert s group,.e., comparson of matrces. Then the relatve weghts for the avalable alternatves wth respect to the avalable crtera are calculated.
Internatonal Journal of Scentfc & Engneerng Research Volume 2, Issue 7, July-20 4. Par wse comparson wth respect to Modfablty Modfablty PF LA BB PF 3 5 LA /3 3 BB /5 /3 PF 0.652 0.6923 0.5555 LA 0.274 0.2307 0.3333 BB 0.304 0.0769 0. Relatve Prortes for Modfablty s w (0.6333, 0.2604, 0.06) 2. Par wse comparson wth respect to Scalablty Scalablty PF LA BB PF 3 7 LA /3 3 BB /7 /3 PF 0.6774 0.6923 0.6363 LA 0.2258 0.2307 0.2727 BB 0.428 0.0769 0.0909 Relatve Prortes for Scalablty s w2 (0.6686, 0.243, 0.035) 3. Par wse comparson wth respect to Performance Performance PF LA BB PF 7 5 LA /7 3 BB /5 /3 PF 0.7446 0.8400 0.5556 LA 0.063 0.200 0.3333 BB 0.489 0.0400 0. Relatve Prortes for Performance s w3 (0.734, 0.865, 0.000) 4. Par wse comparson wth respect to Cost Cost PF LA BB PF 3 5 LA /3 7 BB /5 /7 PF 0.652 0.724 0.3846 LA 0.273 0.243 0.5384 BB 0.304 0.0344 0.0769 Relatve Prortes for Crteron Cost s w4 (0.5869, 0.3324, 0.0806) 5. Par wse comparson wth respect to Dev. Effort Development Effort PF LA BB PF 3 7 LA /3 3 BB /7 /3 PF 0.6774 0.742 0.5384 LA 0.2258 0.2380 0.3846 BB 0.0967 0.0476 0.0769 Relatve Prortes for Dev. Effort s w5 (0.6433, 0.2828, 0.0737) Par wse comparson wth respect to Probablty Probablty PF LA BB PF /7 3 LA 7 /5 BB /3 5 PF 0.200 0.0232 0.742 LA 0.8400 0.627 0.0476 BB 0.0400 0.839 0.2380 Relatve Prortes for Probablty s w6 (0.2858, 0.350, 0.3640) 6. Par wse comparson wth respect to Ease of Use Ease of Use PF LA BB PF 7 3 LA /7 7 BB /3 /7 PF 0.6774 0.8596 0.2727 LA 0.0967 0.228 0.6363 BB 0.2258 0.075 0.0909 Relatve Prortes for Ease of Use s w7 (0.6032, 0.2853, 0.4) Relatve Importance Matr Calculatons for the above stated crtera: Par wse comparson for Crtera W M S P C E Pr Eu M 3 3 5 7 3 7 S /3 3 5 3 7 3 P /3 /3 3 5 5 7 C /5 /5 /3 5 7 3 E /7 /3 /5 /5 7 5 Pr /3 /7 /5 /7 /7 3 Eu /7 /3 /7 /3 /5 /3 Normalzed Par-wse Comparson Matr: W M S P C E Pr Eu M 0.4022 0.564 0.3808 0.3406 0.3279 0.0989 0.243 S 0.340 0.87 0.3808 0.3406 0.405 0.2307 0.034 P 0.340 0.0623 0.269 0.2044 0.2342 0.648 0.243 C 0.0804 0.024 0.0423 0.068 0.2342 0.2307 0.034 E 0.0574 0.0623 0.0084 0.036 0.0468 0.2307 0.724 Pr 0.340 0.007 0.0084 0.009 0.0066 0.0329 0.034 Eu 0.0574 0.0623 0.002 0.0006 0.003 0.009 0.0344 Relatve Importance Matr: W M S P C E Pr Eu RowAvg M 0.4022+0.564+0.3808+0.3406+0.3279+0.0989+0.243/7 0.336 S 0.340+0.87+0.3808+0.3406+0.405+0.2307+0.034/7 0.267 P 0.340+0.0623+0.269+0.2044+0.2342+0.648+0.243/7 0.668 C 0.0804+0.024+0.0423+0.068+0.2342+0.2307+0.034/7 0.02 E 0.0574+0.0623+0.0084+0.036+0.0468+0.2307+0.724/7 0.0845 Pr 0.340+0.007+0.0084+0.009+0.0066+0.0329+0.034/7 0.042 Eu 0.0574+0.0623+0.002+0.0006+0.003+0.009+0.0344/7 0.0240
Internatonal Journal of Scentfc & Engneerng Research Volume 2, Issue 7, July-20 5.3. Weght Aggregaton After all the relatve weghts are calculated, a composte weght for each decson choce s determned by aggregatng the weghts over the herarchy for decson choce. Calculaton of Relatve Prortes: 0.6333 0.2604 0.06 0.336 0.336 0.336 0.267 0.267 0.267 0.6686 0.734 0.5869 0.6433 0.2858 0.6032 0.668 0.668 0.668 0.243 0.865 0.3324 0.2828 0.350 0.2853 0.02 0.02 0.02 0.035 0.000 0.0806 0.0737 0.3640 0.4 0.0845 0.0845 0.0845 0.042 0.042 0.042 0.0240 0.0240 0.0240 0.6220 Normalzed Prorty Matr: 0.6220 Relatve Prorty Vector: 0.6220 0.6220 0.6220 0.6220 Ppes & Flters : 0.6220+0.6220+0.6220/3 = 0.622 Layered Style : ++/3 = 0.253 Black Board : ++/3 = 0.0 The fnal results obtaned n the AHP Phase are (PF, LS, BB) = (0.622, 0.253, 0.0). These weghts are used as prortes n goal programmng formulaton. That s (PF, LS, BB) = ( w, w2, w 3 ) = (0.622, 0.253, 0.0) are the values of the three archtecture styles. The weght vector obtaned from the above AHP model s used to optmze the soluton further by zero-one goal programmng as follows: There est several oblgatory and fleble goals that must be consdered n the selecton from the avalable pool of three archtecture styles. There are three oblgatory goals: () a mamum tme of 24 workng days s requred to select the best archtecture style, (2) a mamum duraton of 35 months s requred to complete the software proect and (3) a mamum budget of $ 20,000 s allocated to develop the proect [4]. In addton to the oblgatory goals of selectng the best archtecture style, there are two other fleble goals, stated n order of mportance: () allocaton of budget s set at $20,000 and (2) allocaton of mscellaneous fees s set at $4200, devaton from ths allocaton s not allowed. In the followng table, the cost and resource usage nformaton for each of the three styles s presented. Table. Cost and resources usage nformaton Proect resource usage ( a ) Plannng and desgn days 2 3 b 0 24 8 24 days Constructon months 32 34 30 35 months Budgeted cost (00) $50 $300 $280 $300 Msc cost (00) $8 $24 $5 $42 Based on the weght vector computed usng AHP, we can formulate the goal constrants n the followng table. Ths ZOGP model s solved usng LINDO Ver 6.. The results are summarzed as follows: Table. ZOGP model formulaton ZOGP model formulaton Mnmze Z = ( d d 2 d3 ) pl (0.622d 0.253d 0.0d ) Goals pl Satsfy all oblgatory goals pl d d ) 4 ( 4 4 Select hghest AHP weghted 2 5 6 7 archtecture styles ( Use $20,000 for all archtec- pl 3 d 8 d 8 ) ture styles selected Use $4200for all archtecture styles selected Subect to 0 24 8 Avod over utlzng ma. X X X d d 24 2 3 plannng and desgn days 32 34 30 Avod over utlzng ma. X X X d d 35 2 3 2 2 constructon months Avod over utlzng ma. 50X 300X 280X d d 300 2 3 3 3 budgeted dollars X d 5 Select Layered Style (LS) X 2 d 6 Select Ppe & Flter (PF) X 3 d 7 Select Blackboard Style (BB) Avod over or under utlzng 8X 24X 5X d d 42 2 3 4 4 msc cost Avod over or under utlzng 50X 300X 280X d d 300. 2 3 8 8 epected budget X 0 or,2,3 0 2, 3 0 d 0, d 0, d2, d2 0, d3 0, d3 0, d4 8, d4 0, d, d 0, d, d 0, d 0. 5 6 7 8 8 Archtecture Style Ppe & Flter (PF) s chosen as t consumes the total budgeted cost of $30,000 and use 24 days of tme for decson. Also, the selected style wll save one month constructon tme (total tme s 35 months) as. Complance checkng s to be eecuted for every sngle modfcaton made to source code usng the SAVE Tool.
Internatonal Journal of Scentfc & Engneerng Research Volume 2, Issue 7, July-20 6 4 DISCUSSION As organzatons are nfusng more technologes to support busness operatons and enhance organzatonal compettveness, they are lke to fnd that the tradtonal methods such as scorng, rankng methods, Fuzzy logc, etc analyses are unsatsfactory for evaluatng emergng technologes for adopton of decsons. The obectve of ths paper s to provde a systematc process to sort out the avalable alternatves by applyng the decson analyss model, the AHP. However, the comparson of the AHP and other method lke scorng and rankng methods may be napproprate as the AHP s a mult crtera decson technque. Another etenson of ths research could test the wde range of decson problem s a group settng. Ths study of AHP has evaluated n the contet of Software Archtecture selecton. A more comprehensve lst of mult crtera problems, ncludng vared level of dffculty and problem types, should be prepared to gude the systematc evaluaton of the strengths and weakness of AHP. It would perhaps be better f multple mult crtera methods, alongsde multple decson problems, be employed to derve a reference model for the effectveness of mult crtera models. Table Dfferent Technques and Methods Method Multple Crtera Resource Feasblty Optmzaton requred Rankng [4] Yes No No Scorng [5] Yes No No AHP [6] Yes No No Goal Programmng [7] No Yes Yes DynamcProgrammng[8] No Yes Yes AHP-GP [Ths Paper] Yes Yes Yes The proposed model, AHP-GP s to demonstrate the procedure of fndng weght that consders nterdependence among crtera or alternatves [20] whch has hghest weght w. The ZOGP model selects the best archtectural style for whch the weght w s derved from AHP whch has mamum value and mnmum devaton d. Fnally, archtecture Style 2 s chosen whch s optmum as t s consumes the total budget cost of $30,000 and use eactly 24 days of tme for decson. The selected style wll save one month constructon tme (total tme s 35 months) as d 5 CONCLUSIONS 2 Ths paper proposes a goal programmng approach to the selecton of software archtecture style. Ths approach can smultaneously handle the multple and conflctng goals characterstc of the decson problems such as qualty, lmted avalablty of resources. The ntegrated AHP-GP- Vsualzaton model appled n three subsequent stages: the frst part of the analyss provded the prorty levels for the dfferent alternatves (ppe&flter, layered, blackboard) wth respect to the crtera (modfablty, scalablty, performance, cost, effort, portablty and ease of use). In the second step, the Goal Programmng model equatons are formulated for the selecton of the optmal archtecture style based of the goals. In the thrd step, complance checkng s to be eecuted for every sngle modfcaton made to source code usng the SAVE Tool for qualty assurance. The applcaton of the GP technque combned wth AHP methodology proved to be a fleble tool to select the best archtecture style. Accordng to eperts, n selectng a style there s no sngle decson nvolved but n the decsons consderaton may be better or worse but stll sgnfcant. For eample, a style wth a low weght mght be selected over a style wth a hgh weght f developers are more famlar wth the style whch has a lower score. The weght vector obtaned usng AHP for the above eample s (0.622, 0.253, 0.0) [9]. Table 8 shows the comparson among the AHP and AHP-GP approaches. Table Comparson of AHP and AHP-GP approaches Method Plannng and desgn days Resources Used Constructon months Budgeted cost (00) Msc cost (00) AHP 24 35 300 42 AHP-GP 24 34* 300 24** * We wll save one month constructon tme as d 2 ** We wll use only Msc cost $800 (<$4200) more than the ntal Budgeted cost as d 8. 4 6 REFERENCES [] Shaw M., Clements P.: The golden age of software archtecture, IEEE Softw., 2006 [2] Garlan D.: Software archtecture: a roadmap, n Fnkelsten A. (ED.): The future of software engneerng (ACM Press, 2000) [3] Dobrca L., Nemela E.: A survey on software archtecture analyss methods, IEEE Trans. Softw. Eng., 2002 [4] Soung He K., Jn Woo L.: "An Optmzaton usablty of nformaton system proect resources usng a QFD and ZOGP for reflecton customer wants", Korea Advanced Inst of Scence & Tech. [5] Jn Woo Lee, Soung He Km: Usng analytc herarchy process and goal programmng for nterdependent nformaton system proect selecton, Computers & Operaton Research [6] Saaty, T. L., A Scalng Method for Prortes n Herarchcal structures, Journal of Mathematcal Psychology, 984 [7] Saaty and Takzawa: "The Theory of Rato Scale estmaton", Management Scence Vol 33, Nov 987 [8] Glora E., Eugene D.and Gussepp A.,:"A multple-crtera framework for evaluaton of decson support systems", Omega Volume 32, Issue 4, August 2004
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