Sustanablty Proflng of Long-lvng Software Systems Ahmed D Alharth, Mara Spchkova and Margaret Hamlton RMIT Unversty, Melbourne, Australa Emal: {ahmedalharth, maraspchkova,margarethamlton}@rmteduau Abstract Ths paper ntroduces a framework for software sustanablty proflng The goal of the framework s to analyse sustanablty requrements for long-lvng software systems, focusng on usablty and readablty of the sustanablty profles To acheve ths goal, we apply a quanttate approach such as fuzzy ratng scale-based questonnares to rank the sustanablty requrements, and the Technque for Order Preference by Smlarty to Ideal Soluton (TOPSIS) to analyse the results of questonnares and to provde a bass for system proflng The core proflng elements provded by our framework are (1) a sustanablty fve-star ratng, (2) vsualsaton of the fve sustanablty dmensons as a pentagon graph detalng combnaton for ndvdual, socal, techncal, economc and envronmental dmensons, and (3) a bar graph of overall sustanablty level for each requrement To ensure sustanablty, the proposed proflng framework covers the fve dmensons of sustanablty to quantfy the sustanablty of any software system not only durng the requrement gatherng phase but also durng mantenance phase of software system lfecycle I INTRODUCTION Addressng the mpacts of software systems on sustanablty s a frst-class qualty concern besde usablty, safety and securty [1] A number of studes showed that f a software system s developed wthout takng sustanablty requrements nto account, the system could have negatve mpacts on ndvdual, socal, technology, economc, and envronment sustanablty, cf [2] [5] Envronmental awareness s crucal for software engneerng, especally n the case of large-scale systems havng many thousands of users The analyss of system sustanablty has to be ntated on the requrements engneerng (RE) phase [6], [7] Based on ths dea, Becker et al [8] emphassed that the mportance of dentfyng stakeholders whose outsde nterests are affected, and the use of long-lfe scenaros technques durng requrements elctaton could forecast potental mpacts Duffy [9] hghlghted that sustanablty could be acheved especally n the socal dmenson through usablty, whch s a nonfunctonal requrement, and ts tradtonal methodologes Ths queston s especally mportant for long-lvng systems, where the stakeholders requrements and preferences mght change over the tme the system s n use For example, a system that can be seen as sustanable today, mght be rated as envronmentally unsustanable n few years, whle new technques to ncrease envronmental sustanablty are developed To solve ths problem, we requre an easy-to-use proflng framework based on quanttate approaches that would allow to analyse the up-to-date system sustanablty profles, based on system characterstcs and the up-to-date ratngs (quotatons) of the correspondng requrements Usablty and readablty of the approach s crucal to make t applcable for real software development processes, as the quotaton process and the generated profles have to be easy-to-use by all stakeholders Contrbutons: To ensure the sustanablty of long-lvng software systems over ther etre lve-cycle, we propose a framework for sustanablty proflng The framework allows to analyse sustanablty requrements for long-lvng software systems The up-to-date profles could be generated both durng the RE and the mantenance phase of the software system lfecycle The framework workflow s presented n Fgure 1 Frst of all, stakeholders are assgned to a group to rate requrements from the dfferent perspectve of sustanablty dmensons (ndvdual, socal, techncal, economc and envronmental) Then, a fuzzy ratng scale s used to avod mprecson for answerng quanttatve questonnares [1] As the next step, the Technque for Order of Preference by Smlarty to Ideal Soluton (TOPSIS, cf [11]) s utlsed to fnd alternatves that are the nearest dstance from the postve deal soluton and farthest dstance from the negatve deal soluton The software sustanablty proflng ncludes an overall pcture of how sustanable a software system really s The profle s presented as three core elements: (1) a fvestar ratng, (2) fve dmensons of sustanablty n a pentagon graph, and (4) an overall measure of sustanablty for each requrement n a bar graph Outlne: The rest of the paper s organsed as follows In Secton II we dscuss the background and related work Secton III ntroduces our framework for software sustanablty proflng Secton IV ntroduces an example scenaro to show how the framework can be used to profle software systems Secton V summarses the core contrbutons of our work II BACKGROUND AND RELATED WORK In ths secton we dscuss the research drectons and approaches that provde a background for our framework: RE for sustanable systems, the dea of the sustanablty proflng, quanttatve approaches, approaches usng the fuzzy ratng scale, and the TOPSIS framework for requrements analyss We selected TOPSIS for our sustanablty proflng framework, as ths technque has been successfully used for prortsng requrements and solvng conflct among non-functonal requrements, cf [11] [13] Prevously, TOPSIS was used 12
Fg 1 Software Sustanablty Proflng Framework wthout takng nto account the sustanablty aspects, but the extenson to evaluate sustanablty requrements s possble and easy to mplements In the sustanablty dmensons we have the same knd of relatons among requrements: (1) each requrement has mpacts on other requrements, and (2) each requrement has postve or negatve mpacts on sustanablty dmensons that could be maxmsed or mnmsed durng the TOPSIS procedure A Requrements engneerng for sustanable systems The RE phase of software development focuses on dscoverng, developng, tracng, analysng, qualfyng, communcatng and managng system requrements, cf eg, [14] Lam et al [15] proposed to defne a sustanable software process as one whch meets realstc sustanablty objectves, takng nto account not only drect but also ndrect mpacts of the software on economy, socety, human bengs, and envronment Penzenstadler [16] defned RE for sustanablty as the concept of usng requrements engneerng and sustanable development technques to mprove the envronmental, socal and economc sustanablty of software systems and ther drect and ndrect effects on the surroundng busness and operatonal context Sustanablty n software has varous dmensons Goodland [17] suggested to dstngush the followng four dmensons: human (ndvdual), socal, economc and envronmental sustanablty Penzenstadler and Femmer [5] as well as Razavan et al [18] added to the new dmenson of techncal sustanablty In our framework, we analyse the system sustanablty usng the fve dmensons: Indvdual sustanablty: Indvdual needs should be protected and supported wth dgnty and n a way that developments should mprove the qualty of human lfe and not threaten human bengs; Socal sustanablty: Relatonshps of people wthn socety should be equtable, dverse, connected and democratc; Techncal sustanablty: Technology must cope wth changes and evoluton n a far manner, respectng natural resources; Envronmental sustanablty: Natural resources have to be protected from human needs and wastes; and Economc sustanablty: A postve economc value and captal should be ensured and preserved B Sustanablty Proflng Sustanablty proflng has been used mostly for software energy and data centre consumpton, as well as n ctes and urban settlements James [19] hghlghted that a holstc and ntegrated understandng of urban lfe s essental He presented an urban profle framework for ctes sustanablty ncludng four man domans ecology, economcs, poltcs and culture as well as seven sub-domans for each man doman The framework was also appled to the sustanablty of elearnng by Stewart and Khare [2] Ths framework was provdng a nne-pont scale ratng that s mprecse and has to be extended to ft software development process and to cover the correspondng sustanablty dmensons Gmach et al [21] proposed a proflng approach for the sustanablty of data centres, to quantfy energy durng desgn and operaton of data centres Smlarly, Jagroep et al [22] demonstrated a software energy proflng to analyse software changes n energy consumpton between releases of a software product Although both studes focused on energy consumpton that could mpact envronmental and economc dmensons of sustanablty, ndvdual and socal dmensons were gnored n the measurement Our approach covers the fve dmensons of sustanablty to quantfy the sustanablty 13
Step 3 Determnng a support response to be consdered as compatble to some extent; and Step 4 Creatng a trapezodal fuzzy number from the two ntervals, whch are lnearly nterpolated, as T ra(a, b, c, d), where a b c d 1 of any software system, startng from the requrements phase and contnung over the phase of mantenance C Quanttatve Approach Quanttatve approaches are used to analyse data and to measure qualtes n software engneerng [23], [24] For nstance, goal-orented requrements and user experence are analysed and measured va quanttatve technques havng a ratng scale of probablty between satsfacton and denal of satsfacton The ratng scales and data analyss technques vary from one quanttatve approach to another Some approaches use a fvelevel Lkert scale whle others employ a nne-pont scale to present people s atttudes by scalng ther responses Notably, the Lkert ratng scales and the nne scales that are gvng a number of optons are closed format For example, f a questonnare has a closed fve Lkert scale, partcpants can only express ther opnon through one of the fve choces These closed format optons are mprecse, dffcult to choose between and lmted A soluton to overcome drawbacks of closed formatted scales are the fuzzy ratng scale [1], cf Secton II-D for more detals The quanttate approaches can be appled to several types of data, and the type of data to analyse mght nfluence the choce of the approach Tulls and Albert [23] suggest to dstngush the followng four types of data: Nomnal data s categorsed or classfcaton data, whch t s not n any partcular order, eg, gender or har colour; Ordnal data s ordered classfed data, but the dfferences between them are not meanngful, eg, product and move ratngs; Interval data s classfed data where the dfference between two data tems s meanngful, but wthout natural zero ponts, eg, temperature unts; Rato data s nterval data wth absolute zero, eg, weght and heght To analyse sustanablty requrements, we wll create from the provded by stakeholders rankng the correspondng rato data Ths transformaton wll be done usng TOPSIS, cf Secton II-E The rato data wll be then further explored to buld the system profle Fgure 2 presents an example on applcaton the above method to wthn our framework: The scale goes from to 1%, where corresponds to the worst case (crtcal value), and 1 corresponds to the best case (green value) For smplcty, t s also possble to use a scale from to 1, where 1 corresponds to 1% Gr een ( V br ant ) Cr t c al St ep1 Gr een ( V br ant ) Cr t c al St ep2 Gr een ( V br ant ) Cr t c al St ep3 Gr een ( V br ant ) Cr t c al Fg 2 Fuzzy Ratng Scale for Sustanablty Proflng E TOPSIS Technque for Order of Preference by Smlarty to Ideal Soluton (TOPSIS) s an effectve technque to evaluate sustanablty requrements whch change over tme s utlsng TOPSIS s one of the multple crtera decson analyss approaches to dentfy the best alternatve that s nearest to an deal soluton and farthest from negatve deal soluton [12] The prncples of TOPSIS are smple, and postve deal solutons and negatve deal solutons formed [26] The beneft crtera n the postve deal soluton are maxmsed, and the cost crtera are mnmsed, whle the cost crtera n the negatve deal soluton are maxmsed, and the beneft crtera are mnmsed [11] The followng s the stepwse procedure of TOPSIS accordng to Behzadan [11]: Step 1 Construct normalsed decson matrx rj D The Fuzzy Ratng Scale A fuzzy ratng scale (FRS) allows the capturng of the dversty of ndvdual responses n questonnares, also avodng mprecson whle ratng a questonnare [1] For our sustanablty proflng, stakeholders wll be requred to rate the correspondng sustanablty dmensons For example, as an alternatve of stakeholders choce from a fve classfed ratng scale, they can select ther range and extend t between a range of two extreme poles To mplement an FRS, we adopt the fuzzy ratng scale method proposed by Lubano et al [25]: Step 1 Consderng a representatve ratng on the bounded nterval; Step 2 Determnng a core response to be consdered as fully compatble; xj rj = qp m =1, f or = 1,, m, j = 1,, n x2j (1) 14
Step 2 Construct the weghted normalsed decson matrx v j v j = w r j (2) where w s the weght for j crteron Step 3 Determne the postve deal (A ) and the negatve deal solutons (A ): Postve deal solutons A = {max(v j ) j J; mn(v j ) j J } = {v 1,, v n} Negatve deal solutons A = {mn(v j ) j J; max(v j ) j J } = {v 1,, v n} Step 4 Calculate the separaton measures: The separaton from postve deal s S n = (v j v ) 2, = {1,, m} (5) j=1 Smlarly, the separaton from negatve deal s n S = (v j v ) 2, = {1,, m} (6) j=1 Step 5 Calculate the relatve closeness to the deal soluton C C = (3) (4) S (S + S ), < C < 1, = {1,, m} (7) C = 1 f A soluton has the best condton, C = f A soluton has the worst condton III FRAMEWORK FOR SUSTAINABILITY PROFILING The general dea of the framework workflow s presented n Fgure 1 To measure the sustanablty aspects of the requrements, we adopted the FRS approach Requrements are rated aganst sustanablty dmensons, whch gves an nput to the TOPSIS procedure The provded by TOPSIS results wll create a bass for sustanablty proflng: usng these results, our framework determnes (1) the sustanable of each system requrement, (2) sustanablty of the software system as whole Ths wll be presented n a fve-star ratng wthn each level of sustanablty dmensons and the overall sustanablty of each requrement The analytcal approach conssts of the followng fve steps, cf also Fgure 1 A Assgnng Stakeholders Requrements engneers should assgn stakeholders to one of the three stakeholder groups havng end-users, admnstrators, and developers and provders groups For nstance, n elearnng systems the learner and nstructor are n the end-users group whle ITs support could be assgned to the admnstrator group B Defnng Questons The framework wll generate a questonnare ncludng related questons (nstructons) for each requrement wth regard to the sustanablty dmensons and stakeholders groups Thus, for each requrement k questons wll be created, where 1 k 5 Each queston should present a sngle sustanablty dmenson perspectve, whch s covered by the requrement, and have a form Rate the nfluence of the requrement on the X sustanablty, where X s belongs to the set {ndvdual, socal, techncal, envronmental, economc} The generated questonnare can be further revsed and adapted by both requrements engneers and sustanablty experts, before contnung wth the next step For example, requrement R1 has to have fve questons, coverng each dmenson of the sustanablty C Ratng Requrements Each stakeholder has to answer allotted queston from vary vews of certan sustanablty dmenson by usng the FRS For example, stakeholders, who are n the learners and nstructors group, wll answer two questons for each requrement: from the ndvdual and from the socal sustanablty pont of vew and another tme for the socal sustanablty Each answer, also, wll be n a form of trapezodal fuzzy number from the two ntervals as T ra(a, b, c, d), where a b c d 1 D Analysng Sustanablty Usng TOPSIS After all stakeholders answered the questonnare, the results of the FRS approach become nputs for TOPSIS The data wll be normalsed and weghted accordng to Equatons 1 and 2, and after that the steps 3, 4 and 5 of TOPSIS need to be appled twce: Frst round: Applyng requrements as crtera to determne overall sustanablty wthn the separaton of requrements mpacts for each requrement; and Second round: Applyng sustanablty dmensons as crtera to analyss each dmenson wthn all requrements and overall sustanablty ratng for the software E Generatng Software Sustanablty Proflng The result of TOPSIS analyss ncludng two rounds helps to generate software sustanablty proflng whch s vsualsed representng the result The proflng ncludes: Sustanablty fve-star ratng Presentng the average of C n the both rounds of sustanablty dmensons and requrements; Fve sustanablty dmensons Illustratng each dmenson level combned n pentagon or bar graph (optonal) for the software havng all rated requrements; and Bar graph Showng an overall sustanablty for each requrement An example of a sustanablty profle for a software system, whch s created usng the proposed framework, s presented n the next secton (cf Fgure 5) 15
Fg 3 Sustanablty Proflng as a part of RE Actvtes TABLE I THE KEY CHART IN SOFTWARE SUSTAINABILITY PROFILING Percentage % Colour Code Descrpton 8-1 Dark green (Vbrant) 6-79 Lght green Satsfactory 4-59 Yellow Basc 2-39 Orange Unsatsfactory -19 Red Crtcal Consderng a dfferent nformaton n the proflng, we smplfy and vsualse the result by creatng a key chart wth fve categores as shown n Table I Ths key chart ncludes numerc varables n percentage, colour codes for vsualsaton, and lngustc varables as a descrpton Fgure 3 demonstrates how the proposed framework can be uses durng the RE actvtes (we follow the defnton of the RE actvtes ntroduced by [27] [3]): Requrements elctaton s the practce of understandng and determnng stakeholders needs and constrants To rate the sustanablty requrements usng the proposed framework, at ths phase two actons are necessary: (A) the stakeholders have to be assgned, (B) the questonnares have to be generated However, takng nto account the long-lvng nature of the system, re-teraton of these steps mght be necessary on the management phase, to ensure the sustanablty over the software system lfecycle: (A ) new stakeholders can be assgned, (B ) the questonnares can be updated Requrements analyss s the practce of refnng stakeholders needs and constrants by defnng the process, data and object of the requred system On ths phase, we conduct the followng steps of our framework: (C) the stakeholders rate the requrements, (D) the sustanablty of the system s analyses usng TOPSIS, (E) the sustanablty profle s generated To ensure longevty of the system, these steps also can be repeated durng the management phase Requrements specfcaton s the practce of wrtng down stakeholders needs and constrants, and ths documentaton should be unambguous, complete, correct, understandable, consstent, concse, and feasble The sustanablty profle could be seen as one of the nput to the specfcaton phase Requrements valdaton s the practce of checkng that the specfcaton captures users needs and constrants The proposed framework does not cover the valdaton actvtes, whch mght be one of the future work drectons Requrements management s the practce of schedulng, controllng changes and trackng requrements over tme In the case of long-lvng systems, the management actvtes are crucal to keep the software system sustanable The steps (A) (E) have to be repeated to provde an up-to-date sustanablty profle of the system IV APPLICATION OF THE PROPOSED FRAMEWORK Let us dscuss an example scenaro wth fve requrements R1,, R5 The am of ths scenaro s to llustrate applcaton of the proposed framework, wthout gong nto the techncal detals lke generatng of questons wthn real questonnares In ths scenaro, we wll go through all framework steps and present the created sustanablty profle as the fnal result A Assgnng Stakeholders Let us assume that the requrements wll be rated by ten assgned stakeholders: four n the end-users group, three n admnstrators group, and three n developers and provders group B Defnng Questons Ths step s omtted n the example, as the ratng actvtes wll be smulated C Ratng Requrements To smulate the ratng actvtes where each stakeholder rates requrements aganst sustanablty dmensons by answerng defned questons, we generate random numbers between [:1] ( corresponds to a crtcal value, 1 corresponds to a green value) for the fuzzy ratng scales Fgure 4 shows the results of applcaton of the FRS approach to the requrement R1, from the prospectve of ten assgned stakeholders As follows from Fgure 4, Stakeholder S2, who s assgned to ndvdual and socal sustanablty dmensons, rates R1 for 16
Crtcal A Representatve Ratng ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Indvdual Crtcal S 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Socal Crtcal S 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Indvdual Crtcal S 2 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Indvdual Crtcal S 3 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Indvdual Crtcal S 4 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Socal Crtcal S 2 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Socal Crtcal S 3 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Socal Crtcal S 4 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Socal Crtcal S 5 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Socal Crtcal S 6 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Socal Crtcal S 7 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Envronment Techncal Economc Economc Crtcal S 5 Crtcal S 5 Crtcal S 8 Crtcal S 8 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Envronment Techncal Economc Economc Crtcal S 6 Crtcal S 6 Crtcal S 9 Crtcal S 9 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Envronment Economc Techncal Economc Crtcal S 7 Crtcal S 7 Crtcal S 1 Crtcal S 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Envronment Crtcal S 8 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Crtcal S 9 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Envronment Envronment Crtcal S 1 ( Vbrant ) 1 2 3 4 5 6 7 8 9 1 Fg 4 Example of Fuzzy Ratng Scale for Requrement (R1) TABLE II OUTPUT EXAMPLES OF FUZZY RATING SCALE FOR REQUIREMENTS ANALYSIS R1 R2 R3 R4 R5 Dmenson S1 S2 S3 S4 S5 S6 S7 S8 S9 S1 Indvdual 573 754 625 914 Socal 276 727 87 917 377 942 66 Techncal 579 88 324 Economc 158 446 34 345 362 529 Envronment 382 351 799 291 986 13 Indvdual 281 472 232 289 Socal 96 587 65 31 66 455 47 Techncal 925 677 39 Economc 93 56 738 567 459 395 Envronment 224 794 781 362 642 18 Indvdual 966 379 974 59 Socal 3 331 17 717 835 128 99 Techncal 173 157 728 Economc 182 1 473 5 366 54 Envronment 257 282 187 814 711 688 Indvdual 287 82 347 361 Socal 12 376 318 976 785 381 88 Techncal 583 667 32 Economc 163 417 547 599 36 821 Envronment 244 871 953 13 222 249 Indvdual 619 546 957 614 Socal 6 5 46 3 977 535 518 Techncal 215 995 943 Economc 244 72 328 251 349 61 Envronment 214 74 662 949 714 583 ndvdual perspectve as T ra(51, 66, 856, 1) whle socal perspectve as T ra(6, 66, 75, 9) We calculate fuzzy values from each fuzzy ratng by mean measurement, so ndvdual and socal means of R1 for S2 are 754 and 727, respectvely D Analysng Sustanablty In the next step, all the FRS outputs become nputs for TOPSIS, cf Table II These data are normalsed accordng to Equaton 1 for the fve system requrements R1,, R5 wthn the ndvdual, socal, techncal, economc and envronmental dmensons of sustanablty The result of normalsaton step presented n Table III The weghted normalsaton that was constructed accordng to Equaton 2 s showed n Table IV Followng the TOPSIS procedure, we calculate for both rounds the separaton measures from postve deal S and negatve deal solutons S, as well as the relatve closeness C The results are summarsed n Tables V and VI Noteworthy, we could calculate the negatve mpact of economc and envronmental sustanablty dmensons va the negatve deal soluton that maxmses the cost crtera and mnmses the beneft crtera E Sustanablty Proflng The generatng software sustanablty proflng s presented n Fgure 5 wthn an overall of 49% sustanablty whch s the mean of C n the two rounds (n Table V and VI) Among 17
Indvdual Socal R5 R4 Economc Techncal R3 R2 R1 2 4 6 8 8 1 % 6 79 % 4 59 % 2 39 % 19 % (Vbrant) Satsfactory Basc Unsatsfactory Crtcal Envronmental Overall 1 3 5 7 9 Fg 5 Sustanablty Profle of a Software System usng the default colour schema To ncrease accessblty of our approach, we also provde another colourng opton for colour-challenged people In ths opton the red colour s replaced by blue TABLE III THE NORMALISATION DECISION (STEP 1) USING EQUATION 1 Dmensons R1 R2 R3 R4 R5 Indvdual 536 238 529 336 512 Socal 462 423 425 498 422 Techncal 444 496 275 48 559 Economc 421 533 34 562 358 Envronment 431 414 431 374 561 TABLE IV THE WEIGHTED NORMALISATION STEPS FROM EQUATION 2 Dmensons R1 R2 R3 R4 R5 Indvdual 146 33 166 63 126 Socal 85 81 84 18 67 Techncal 97 136 43 89 144 Economc 58 15 35 113 4 Envronment 81 84 94 66 128 TABLE V RESULTS OF THE STEPS 4 AND 5 IN THE FIRST ROUND Dmensons S* S C* Indvdual 917 13 586 Socal 143 118 452 Techncal 134 137 55 Economc 132 14 44 Envronment 93 151 617 TABLE VI RESULTS OF THE STEPS 4 AND 5 IN THE SECOND ROUND R1 R2 R3 R4 R5 S* 116 139 135 191 121 S 179 91 154 88 119 C* 67 394 533 317 497 the fve requrements, R1 meets the hghest level as satsfactory as well as envronmental dmensons Also, ndvdual, socal, techncal and economc dmensons become basc as the lowest level of software sustanablty ncludng the fve requrements n ths example V DISCUSSION AND CONCLUSIONS In ths paper, we ntroduced a framework for software sustanablty proflng We also presented and example scenaro to provde a numercal llustraton on how the framework can be appled The framework allows to create the followng proflng elements: 1) Sustanablty fve-star ratng for overall sustanablty rankng of entre software requrements; 2) Vsualsaton of the fve sustanablty dmensons as a pentagon graph (and, optonally, also a bar graph) for all dmenson levels of the entre software requrements; and 3) Bar graph for overall sustanablty of each requrement In our framework we apply a quanttatve approach to measure sustanablty of the software systems The fuzzy ratng scale s utlsed to overcome nexplct choces n questonnares and ncrease the usablty of the framework The TOPSIS approach for requrements analyss s used to analyse rankng wthn the best deal soluton and the worst deal soluton among requrements that could assst to recognse the postve and negatve mpacts on sustanablty va maxmsng or mnmsng the beneft or cost In the case of long-lvng systems, t s crucal to keep the software system sustanable over the whole lfecycle of the system The stakeholders requrements and preferences mght change over the tme the system s n use, and proposed framework allows to analyse the up-to-date system sustanablty profles, based on system characterstcs and the up-to-date ratngs (quotatons) of the correspondng requrements One of the core features of the framework s readablty of the sustanablty profles, whch also mples the usablty of the proposed framework For example, we apply the fvestar ratng to present sustanablty ratngs, as ths ratng s perceved as a common one n other areas: the fve-star ratng has become a standard for electrcty consumpton labellng n electronc applances such as ar condtoners and computer 18
montors, allowng an energy effcent choce by reducng energy use and emssons (e, to ncrease envronmental sustanablty) We follow the traffc lghts colourng schema, where crtcal values are marked red and green (vbrant) are marked green to ncrease readablty and graphc vsualsaton These colours and ther descrptons have been used n IT and Sustanablty Developments To ncrease accessblty of our approach, we also provde another colourng opton for colourchallenged people, where the red colour s replaced by blue Fnally, there are two optons to present the fve sustanablty dmensons as a pentagon or bar graph because t mght be argued that the pentagon graph could be harder to read and need more effort to analyse represented data than the bar graph, so we provde the bar graph opton for representng the fve sustanablty dmensons Future work: The man drecton of our future work on the proposed framework s to develop a tool for software sustanablty proflng, allowng to perform the framework steps wthn a sngle platform We also would lke to apply the proposed framework to our earler work on the analyss of the RE aspects of ELearnng systems [31] as well as of geographcally dstrbuted systems and wthn global product development [32] [34] ACKNOWLEDGEMENT The frst author s supported by a scholarshp from Umm Al-Qura Unversty, Saud Araba REFERENCES [1] B Penzenstadler, A Ratur, D Rchardson, and B Tomlnson, Safety, securty, now sustanablty: The nonfunctonal requrement for the 21st century, Software, IEEE, vol 31, no 3, pp 4 47, 214 [2] F Berkhout and J Hertn, Impacts of nformaton and communcaton technologes on envronmental sustanablty: Speculatons and evdence, Report to the OECD, Brghton, vol 21, 21 [3] P Lago and T Jansen, Creatng envronmental awareness n servce orented software engneerng, n Servce-Orented Computng Sprnger, 211, pp 181 186 [4] S Naumann, M Dck, E Kern, and T Johann, The greensoft model: A reference model for green and sustanable software and ts engneerng, Sustanable Computng: Informatcs and Systems, vol 1, no 4, pp 294 34, 211 [5] B Penzenstadler and H Femmer, A generc model for sustanablty wth process- and product-specfc nstances, n Proceedngs of the 213 Workshop on n/by Software Engneerng, ser GIBSE 13 New York, NY, USA: ACM, 213, pp 3 8 [6] G G Calenes, Requrements prortzaton framework for developng green and sustanable software usng anp-based decson makng, 213 [7] B Penzenstadler, Infusng green: Requrements engneerng for green n and through software systems, Chrstopher Arcnega, Brgt Penzenstadler TechReport UCI-ISR-14-2 June, 214 [8] C Becker, S Betz, R Chtchyan, L Duboc, S M Easterbrook, B Penzenstadler, N Seyff, and C C Venters, Requrements: The key to sustanablty, IEEE Software, vol 33, no 1, pp 56 65, Jan 216 [9] V G Duffy, Improvng Sustanablty through Usablty Cham: Sprnger Internatonal Publshng, 214, pp 57 519 [1] S de la Rosa de Sáa, M A Gl, G González-Rodríguez, M T López, and M A Lubano, Fuzzy ratng scale-based questonnares and ther statstcal analyss, IEEE Transactons on Fuzzy Systems, vol 23, no 1, pp 111 126, Feb 215 [11] M Behzadan, S K Otaghsara, M Yazdan, and J Ignatus, A state-of the-art survey of TOPSIS applcatons, Expert Systems wth Applcatons, vol 39, no 17, pp 13 51 13 69, 212 [12] D Marza, D Zowgh, and V Gervas, Utlzng TOPSIS: A Mult Crtera Decson Analyss Technque for Non-Functonal Requrements Conflcts, n RE, ser Communcatons n Computer and Informaton Scence, D Zowgh and Z Jn, Eds Sprnger, 214, vol 432, pp 31 44 19 [13] P Achmugu, A Selamat, R Ibrahm, and M N Mahrn, A systematc lterature revew of software requrements prortzaton research, Informaton and Software Technology, vol 56, no 6, pp 568 585, 214 [14] E Hull, K Jackson, and J Dck, Requrements engneerng Sprnger Scence & Busness Meda, 21 [15] G Lam, F Fabbrn, and M Fusan, Software Sustanablty from a Process-Centrc Perspectve, ser Communcatons n Computer and Informaton Scence Sprnger Berln Hedelberg, 212, vol 31, ch Systems, Software and Servces Process Improvement, pp 97 18 [16] B Penzenstadler, n Software Engneerng Cham: Sprnger Internatonal Publshng, 215, ch From Requrements Engneerng to Requrements Engneerng, pp 157 186 [17] R Goodland, Sustanablty: human, socal, economc and envronmental, Encyclopeda of Global Envronmental Change John Wley & Sons, 22 [18] M Razavan, G Procaccant, D A Tamburr et al, Four-dmensonal sustanable e-servces, EnvroInfo, Sep, 214 [19] P James, Urban sustanablty n theory and practce: crcles of sustanablty Routledge, 214 [2] B Stewart and A Khare, elearnng and the sustanable campus, n Transformatve Approaches to Sustanable Development at Unverstes Sprnger, 215, pp 291 35 [21] D Gmach, Y Chen, A Shah, J Rola, C Bash, T Chrstan, and R Sharma, Proflng sustanablty of data centers, n Proceedngs of the 21 IEEE Internatonal Symposum on Sustanable Systems and Technology, May 21, pp 1 6 [22] E A Jagroep, J M van der Werf, S Brnkkemper, G Procaccant, P Lago, L Blom, and R van Vlet, Software energy proflng: Comparng releases of a software product, n Proceedngs of the 38th Internatonal Conference on Software Engneerng Companon, ser ICSE 16 New York, NY, USA: ACM, 216, pp 523 532 [23] T Tulls and B Albert, Measurng the User Experence, 2nd ed, ser Interactve Technologes Boston: Morgan Kaufmann, 213 [24] J Horkoff and E Yu, Analyzng goal models: Dfferent approaches and how to choose among them, n Proceedngs of the 211 ACM Symposum on Appled Computng, ser SAC 11 New York, NY, USA: ACM, 211, pp 675 682 [25] M A Lubano, S de la Rosa de Sa, M Montenegro, B Snova, and M ngeles Gl, Descrptve analyss of responses to tems n questonnares why not usng a fuzzy ratng scale? Informaton Scences, vol 36, pp 131 148, 216 [26] J R S C Mateo, TOPSIS London: Sprnger London, 212, pp 43 48 [27] R H Thayer and M Dorfman, Software Requrements Engneerng Wley-IEEE Press, 2, ch Introductons, Issues, and Termnology, pp 3 4 [28] B Nusebeh and S Easterbrook, Requrements engneerng: A roadmap, n Proceedngs of the Conference on The Future of Software Engneerng, ser ICSE New York, NY, USA: ACM, 2, pp 35 46 [29] P Sawyer, I Sommervlle, and S Vller, Requrements process mprovement through the phased ntroducton of good practce, Software Process: Improvement and Practce, vol 3, no 1, pp 19 34, 1997 [3] I Sommervlle, Software Engneerng, 9th ed USA: Addson-Wesley Publshng Company, 21 [31] A D Alharth, M Spchkova, and M Hamlton, Requrements engneerng aspects of elearnng systems, n Proceedngs of the ASWEC 215 24th Australasan Software Engneerng Conference ACM, 215, pp 132 133 [32] M Spchkova and H Schmdt, Requrements engneerng aspects of a geographcally dstrbuted archtecture, n 1th Internatonal Conference on Evaluaton of Novel Approaches to Software Engneerng (ENASE 215), 215 [33] M Spchkova, H W Schmdt, M R I Nekv, and N H Madhavj, Structurng dverse regulatory requrements for global product development, n Requrements Engneerng and Law IEEE, 215, pp 57 6 [34] M Spchkova, H Lu, and H Schmdt, Towards qualty-orented archtecture: Integraton n a global context, n European Conference on Software Archtecture Workshops ACM, 215, p 64