Combining Agile Model with Lean Principles to Improve Scrum Model Methodology in Software Companies

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1 Internatinal Jurnal f Innvatin and Scientific Research ISSN Vl. 21 N. 2 Apr. 2016, pp Innvative Space f Scientific Research Jurnals Cmbining Agile Mdel with Lean Principles t Imprve Scrum Mdel Methdlgy in Sftware Cmpanies Gul Naz and Nayyar Iqbal Department f Cmputer Science, University f Agriculture, Faisalabad, Pakistan Cpyright 2016 ISSR Jurnals. This is an pen access article distributed under the Creative Cmmns Attributin License, which permits unrestricted use, distributin, and reprductin in any medium, prvided the riginal wrk is prperly cited. ABSTRACT: In this research a prcess mdel is prpsed fr sftware cmpanies t vercme scrum prcess issues with the cmbinatin f agile mdel and apprpriate lean principles withut cmprmising its benefits and evaluate its success in five different sftware develpment cmpanies. Scrum is widely used agile develpment methd that put prminence n the crss functinal and self-rganized teams wrking in small items called sprints t regularly cnstruct entire increment f prduct. It heavily depends upn the peple and prject due t flexibility in requirement change. Mrever, Sftware develpment managers, prject managers and team lead engineers unsure hw t apply agile methds with lean principles, hw t minimized develper and team management verlad and hw t prmte interest in team members. Many rganizatin fail in getting success and prper benefits frm scrum as it is difficult t handle large and cmplex prject that invlve weak value flw, team level and multiple team level issues. In sftware develpment t much develper verlad due t extra features makes the prject heavy weight. N prper mdel is yet intrduced which implement lean principles in Agile mdel, If prper eliminate waste principles are used in scrum prcess it will prvide better and light weight imprved prcess. KEYWORDS: ASD, Lean Sftware develpment, Traceability, Agile methds, Prject Management, Scrum. 1 INTRODUCTION Sftware develpment prcess is a cntrllable apprach in sftware engineering that facilitates sftware team t deliver quality sftware in timely manner and satisfy the stakehlders and custmer by selecting the apprpriate task, actins and set f wrk activities. Each f these activates cllectin f wrk and actins exist in a mdel r framewrk that identifies their assciatin between them and with the prcess. Prcess mdel rganized the prject int activities help the team and prject manager t wrk in a prper sequence [1]. Agile methds have been prven t be valuable in small sftware teams. Hwever, it has been fund t be a challenge t achieve same value in large scale sftware develpment teams. In missin critical prjects Lean thinking has been cnsidered as enterprise perspective way t surpasses limitatin in scaling ASD. Lean ideas appeared in the manufacturing and started in industry and cnsidered key success driver f Japanese industry [2]. Quality f sftware depends upn the prcess f sftware develpment and prcess cnsidered t be successful if it is being cmpleted accrding t schedule and fulfill the custmer requirements. Sftware develpment is always assciated with uncertainty due t dynamic requirements. Agile methdlgies is flexible apprach and suitable t handle dynamic requirements. N significant empirical evidences are reprted n the successful adaptatin f agile methds. Scrum is mstly used in sftware cmpanies it prvide quality and cst but there are sme issues and challenges while cmpanies are trying t adpt and transfrmatin frm plan driven apprach t agile. Lean wrks with value streams and prvide management with high prgress visibility. An inclusive develpment cycle accmplishing all the lean principle with agile cmbinatin, requirement tractability has nt been prpsed yet. This research will frmulate a mdel with a hybrid apprach f lean and scrum prcess. The prpsed mdel cnsists n the phases f agile mdel with scrum prcess. Crrespnding Authr: Gul Naz 446

2 Gul Naz and Nayyar Iqbal 2 BACKGROUND Wang cnducted secndary data analysis t examined hw agile and lean methdlgies have been cmbined in cntext f sftware develpment prcess and categrized six appraches f cmbine use f bth methdlgies that are nnpurpseful, using Lean t cllabrate with ther business areas while maintaining Agile, cmbinatin f Agile practices and Lean principles and tl, applying lean and agile develpment principles tgether, agile practice with lean techniques t imprve sftware develpment. It has been nt stated prper mdel fr cmbinatin f Agile. Hwever, It has stated that the cmbinatin types and success f sftware develpment is depends upn the needs and situatins f the rganizatins [3]. Balachander et al. described the implementatin f lean cncept and flw n agile sftware develpment. In an industrial web based prject that was executed by agile develpment experienced team. It has been cnducted a case study t find hw lean cncept implemented n agile sftware develpment methdlgy. It described the imprtant factrs that are limited t the prject the bundaries within which these can be used, ding valuable wrk with the high degree f cllabratin f team member and custmers. In a prductin-ready state test and staging prductin envirnments has been prviding the handiness t the team t always retain the system. It significantly reducing the risk typically assciated with prgress t prductin. Highly skilled team, Cding standards and engineering appraches als cntributed greatly twards this [4]. Ali [5] cnducted an nline survey in Pakistan t find ut the challenges and benefits f agile sftware develpment. The wrk identified that lack f experience f scrum master team leader and the prject manager are the biggest issue. There is n cnsideratin n the training as mst f the cmpanies are recently shifted frm traditinal t agile develpment. Mrever it is difficult t handle cmplexity f prject with small teams. It has been examined that prductivity, custmer satisfactin, time t market and quality are advantages f the agile methdlgy. Ahmad et al., (2013) bserved the results frm a literature survey and identified the btained benefits and related challenges t adpt Kanban in agile sftware develpment. It has explred new research pprtunities fr the researchers. This paper has identified a greater number f studies n Kanban practice in sftware develpment. The recent publicatin trend indicates that Kanban is gaining trust in the sftware engineering dmain. A high percentage f the primary studies appear t be experience reprts (47%); and mst f the studies invlved small-scale prjects, t the Kanban apprach. Based n this, sftware engineering has been demanded fr mre brad and precise scientific research n Kanban [6]. Jnssn et al., (2013) bserved frm a literature survey that lean thinking culd be transfrmed t a framewrk. This framewrk culd be prviding difference between lean cncept and agile methd and prvide guidelines hw t apply lean cncept in sftware develpment prcess. Befre this study lean and agile ften use as interchangeable terms but it has been claimed that bth terms are different. This prpsed framewrk has a ptential t cmplement the view f ther researchers and shw t the practitiners what lean sftware develpment in reality is. Althugh the framewrk is develped in a traceable and extensible manner but validatin is necessary fr prperly use [7]. Rdríguez et al., (2014) analyzed the transfrmatin t Lean in the backgrund f sftware develpment at Ericssn R&D Finland. Authrs have explred hw Lean principles in sftware develpment are put int practice and the challenges that cmmence when implemented Lean. Tw majr cntributins f the research is t analyzed main factrs that helped Ericssn R&D s achievements,identified elements such as cntinues integratin, cmmunities f practice, netwrk f prduct wners etc and categrized challenges in implementatin f Lean Sftware Develpment. This study has been prvided evidences f cmpatibilities between Lean and Agile [8]. 2.1 AGILE MODEL Agile practices are a subset f evlutinary and iterative prcesses and are based n iterative imprvement. In all iterative artifacts, iteratin is a self-cntained, small prject with mini activities that cver requirements analysis, design, implementatin, and test. Agile sftware develpment methds were develped as remedy fr the heavy weight methds weaknesses Plan-driven methds r heavy weight prcess are begun with the supplicatin and dcumentatin f a set f requirements that is as cmplete as achievable. [9]. A grup f prficient s in a cllective nature intrduced ASD prcess as a slutin t vercme issues f traditinal methdlgies but Agile manifest prvides the prper and detailed intrductin f Agile prcess t the sftware industry. The agile manifest is based n fur basic nrms: Interactins and Individuals ver tls and prcesses, Wrking sftware with cmplete dcumentatin, Cllabratin f custmer ver agreement negtiatin, and Respnding t change accrding t plan [10]. ISSN : Vl. 21 N. 2, Apr

3 Cmbining Agile Mdel with Lean Principles t Imprve Scrum Mdel Methdlgy in Sftware Cmpanies The custmers were becming less able t state their needs prperly due t rapid change in sftware technlgies, sftware industry and custmers expectatins. As a result, agile methdlgies emerged as an endeavr t mre prperly embrace higher rates f requirements change. The Agile Manifest cntains twelve underlying principles, namely: i. Rapid delivery fr satisfactin f Custmer ii. Always ready fr changing requirements iii. Frequently delivered a wrking sftware iv. Always cnsidered as principal measure f success t wrking sftware v. T maintain a cnstant rate, cnsidered sustainable develpment vi. Meetings are require between stakehlder and develpers fr daily cperatin vii. Face t face cnversatin viii. Mtivated individuals and trusted build the prjects ix. Technical excellence by gd design and Cntinuus attentin x. Simplicity xi. Self rganizing teams xii. Regular adjustment t changing situatins 2.2 SCRUM Sftware develpment prcedure implements scrum technique fr managing the sftware develpment prjects. The main purpse f Scrum is t develp a flexible prduct; therefre it is cmpetent t early respnd t changes required by custmers. Figure 1 represents the Scrum life cycle. The prduct in scrum is described in frm f user stries, which depicts functinality frm a custmer viewpint. The develpment is being carried alng time bxes r incremental tasks, called sprints (iteratins). Each sprint defined a sprint bjective during planning meeting, including the user stries that being assumed during distinct sprint. The sprint backlg that has been selected frm the prduct backlg is being fixed during the sprint. After every sprint, tw defined meetings are cnducted t review prject current state, and expsitin meeting t reveals abut the methd f wrking. Three main rles in Scrum are Prduct Owner, Scrum Team and SM (Scrum Master) [11]. The scrum lifecycle cnsist n the fllwing simple phases. First phase is planning in this phase expectatin and visin is established and funding fr the prject is secured, Figure 1: Scrum life Cycle secnd phase is Staging this stage requirement are priritized fr first sprint( iteratin ) develpment and implement a wrkable prduct, last phase is release in which prduct is deliver as shwn in fig APPLICATION OF LEAN THINKING IN SOFTWARE DEVELOPMENT PROCESS Mary and Tm Pppendieck saw the applicatin f the lean thinking in 2007 at wrk in a Tyta prductin system. After they saw the advantages f the Lean Principles, they published a bk named Lean Sftware Develpment: An Agile Tlkit which directin t the applicatin f Lean Principles in Sftware Develpment prcess. Recently Pppendieck and Cusuman (2012) have described seven lean principles fr sftware develpment which is based n successin experiences. Authrs prpsed thinking lean as a set f principles cmparatively thinking a set f practices [12]. ISSN : Vl. 21 N. 2, Apr

4 Gul Naz and Nayyar Iqbal They applying lean principles in sft-ware develpment prcess t make mre sense and increase quality f prduct. The lean principles fr sftware develpment are: Eliminatin f waste Enhancement f Quality Creatin f the knwledge Cmmitment Deferment T deliver the prduct fast Peple shuld be respected Optimizatin the whle Thse features that have n value fr custmer eliminatin f these feature is called Eliminatin f waste. Waste is the enemy in a system and Value is the basis f any imprtant prduct, and is specified by the custmer. Value means what the custmer wants the prduct t d. Enhancement f quality means built quality alng the develpment phases instead after the cmpletin f develpment stages. Creatin f the knwledge means ver all sftware develpment methd is like t be a knwledge prviding prcess, the deferment cmmitment means there shuld be n hurry and decisins shuld nt be made as late as pssible [13]. T deliver the prduct fast principle is imprtant fr custmers and averts t change their mind instantly. The ptimizatin f the whle means wrk shuld cntinue cnstantly as lng n expldes in develpment directs t success. Different authrs were suggested different practices fr sftware develpment t attain the lean principles are listed as fllwing Just-in-time (JIT), Kanban, Kaizen, Make everything visible, Cst f delay, Value stream mapping and Queuing Thery[14]. (Wmack and Jnes, 2003) shwn in Fig.2. Figure 2: Lean principles benefits in Lean Scrum Sftware develpment Mdel 3 LEAN SCRUM SOFTWARE DEVELOPMENT MODEL The framewrk is cnsisted n the quality assurance steps including lean practices. The steps Included: i) Current Prject Initiatin, ii) Set Quantifiable Gals and Missin, iii) Priritized the Gals, iv) Chsing prcess mdel, v) Execute Prcess, vi) Analyze Prcess and perfrm develpment is the main task fr lean develpment prcess. Metrics thse are included in LSSD Mdel are: firstly Requirement specificatins, Change Requests, remve burdens frm develper and reduce defects, wastes cntrl thrugh traceability all have been included. Fig.3 shws prpsed mdel. ISSN : Vl. 21 N. 2, Apr

5 Cmbining Agile Mdel with Lean Principles t Imprve Scrum Mdel Methdlgy in Sftware Cmpanies Figure 3: Lean Scrum Sftware develpment Mdel 3.1 PROJECT INITIATION Prject initiatin activity cnsists f all the activities which are necessary t be carried ut prir t the start f develpment, such as: Create Prject Visin Initial Infrastructure Initial requirement Identify Scrum Master and Stakehlder Frm Scrum Team Develp Epic Release Planning (Release Planning Schedule) Create Priritized Prduct Backlg 3.2 PRODUCT BACKLOG The prduct backlg is mst imprtant artifact and structured list f everything that may be required in the prduct develpment and is the main surce f requirements fr any changes t be made. The things thse have been identified in this phase f develpment cycle are: Detailed analysis dcument, which summarizes requirement fr prduct. It will be breaks the big-picture stry int Prduct Backlg Items that are manageable increments f wrk Prduct Owner Priritized the sprint that which sprint is crucial t implement first Requirement Traceability ISSN : Vl. 21 N. 2, Apr

6 Gul Naz and Nayyar Iqbal 3.3 SPRINT PLANNING The lean principle specifies value is used t select a sprint n the basis f value given by the custmer. Every sprint will be started with planning meeting which reviews stries frm the Prduct which will be mved t next. Team will be independent t decide hw and what the wrk is perfrmed. All lean principles are used in sprint planning. The Prduct Owner can terminate a Sprint, which shuldn t ccur ften, and wuld usually happen due t a rapid change in business requirements. The Prduct Owner supprts develpers t fcus n instant gals, and gives custmers a tangible based view f prgress. 3.4 SPRINT DESIGN A Design Sprint phase prvides flexible prduct design structure that serves t explit the chances f ding smething peple want. It is cncentrated effrt cnducted by a tiny team, A Sprint Master identifies the design challenge, brings the team tgether and gets a hlds thrugh all sprint stages. A Sprint design phase decreases the risk f dwnstream errrs and generates visin-led gals. The Sprint Design Phase cnsists f five discrete activities: Understand backgrund and user insights Brainstrm what s pssible Rank slutins, pick ne Create a minimum viable cncept RCC rule has been wrking t cntrl the change, there are three steps have been included in requirement change cntrl principle. Thse cnsist f: Planning, Trying and checking; either the change is applicable r nt. 3.5 SPRINT CODING A sprint cde phase is getting develpers fr a specific amunt f time fr just writing cde. Eliminate waste principle is used here t minimized develper verlad. Develper will learn frm each ther s and nt fcus n instructin. During cding they fllw the eliminate principle t reduce time. 3.6 SPRINT TESTING In this step f develpment cycle the imprtant pints t remember are the fllwing: Design f test Cases (There will be ne test case fr each Requirement, every requirement will have its individual test case design fr particularly t check that requirement and with its implementatin.). The fllwing are the test cases have t develp fr the requirements. Unit Test Acceptance Test Integratin Test System Test Functin Test Where unit testing result nly like binary, either success r failure means yes r n. Like unit testing the acceptance test suggests als what is actually the reasn f failure and applicable things can be als tell. Integratin is als called definitin f actin, the testing in which bth parts (sftware and hardware) are cmbined and cmfrt either that they bth can relate and cperate with each ther accrding t custmer expectatins and requirements speciatin s t give the user the required utput. Sftware that must be wrkable frequently is ne f the principles f the lean develpment that it is fr delivering. Which means that the small pieces having functinality cmbined tgether and t make a set f them fr delivery f system. Functin testing is perfrmed t check the functinality either it was the desired utput r nt. T handle change either request t change are apprved r rejected. Remving f errrs and failures Thrugh custmer invlvement ISSN : Vl. 21 N. 2, Apr

7 Cmbining Agile Mdel with Lean Principles t Imprve Scrum Mdel Methdlgy in Sftware Cmpanies 3.7 SPRINT RELEASE In this step f develpment cycle the prduct being develped fully after iteratins and prvided t custmer after prper verificatin and validatin t the custmer. Final activities that are perfrmed in this stage are lessn learned and checkpint. 3.8 DEPLOYMENT After all sprints, the sftware will be deplying fr the custmer in the last step. The prpsed mdel has much capacity t agree t implement new requirements r change the existing requirements based n the custmer demand integrated and the entire sftware will be deplyed t the custmer TRACEABILITY Requirements traceability refers t flw frm rigins f change requirement thrugh its develpment and specificatin, cnsequent deplyment and use, and thrughut all perids f current refinement and sprint in any f these phases. Nt all prjects needs t have traceability but tracing is always useful fr sme prject like large scale and missin critical. Traceability prvides the fllwing advantages in prpsed sftware develpment mdel. Mre transparency, it will be easier fr anyne utside f the team t track the prgress. Reduce risk f lsing infrmatin. Culd result in minimum time searching fr bugs in big systems, the team culd easily lcate where t start lking fr errrs and what tests t fix if they knw what cnstraint that is brken. Pssible t bserve what requirements are tested, designed and validated. 4 THE TOP PRACTICES THOSE HAVE BEEN COMMENCED IN LEAN ARE: Designing at the very begin f a lean prject t identify a feasible technical strategy fr yur slutin there will be desire t d sme preliminary, high-level architectural mdeling. Cntinuus Dcumentatin. Write deliverable dcumentatin in small chunks f develpment during the lifecycle f leanscrum develpment. Active Stakehlder Participatin. Stakehlders and custmers shuld prvide infrmatin in a timely manner; decisin shuld make n time, and in the develpment prcess thrughut the use f systems be as actively invlved. Iteratin Mdeling. At the start f each sprint there will d a chunk f mdeling as part f iteratin planning tasks. Dcument Late. As late as pssible sprint shuld be write dcumentatin, aviding unreal ideas that are in errand f cnstant infrmatin likely t future adjust. Priritized Requirements. Team implement requirements in desire pririty rder, as characterized by their stakehlders. Test-Driven Design (TDD). T accmplish a test write a single test case, either at the level f requirements r at design level. Traceability, t save the recrd f change in requirements. 5 DISCUSSION AND ANALYSIS This sectin shws the results f the survey. Primary data fr this study was cllected thrugh survey questinnaires frm different sftware cmpanies. The surveys were cnducted t evaluate the prpsed Mdel. The survey asked almst 13 questins t verify the usage lean principles and lean scrum mdels in these cmpanies. The questinnaires were nt pen ended s that the resulted culd be analyzed in better statistical frm. The questiner based n the wrking f lean Scrum sftware develpment, if t be valid prcess fr the develpment f sftware. The survey questins included the infrmatin f rganizatin, practitiners, usage f lean principles and its benefits, imprvements f using lean practices and principles and intentins its subsequent t reasns in adptin and the respndents wh agreed t apply this hybrid mdel and wh are nt. Mrever it cnsisted n the infrmatin f the practitiners and their rganizatin. The respnses t surveys by the emplyee f chsen cmpanies driving frce twards the hybrid apprach (lean, Scrum, agile) and advantages cllected. The results are rganized and cmpared with the results f previus methds n agile and lean with cmbined apprach. The ttal number f practitiners wh were answering the survey questins was 30. The practitiners were wrking in different psitin in their rganizatins. The main rganizatinal psitins f the respndents were prject managers, ISSN : Vl. 21 N. 2, Apr

8 Gul Naz and Nayyar Iqbal develpers and Sftware Engineer. Usage f lean scrum sftware develpment apprach in the respndents was reprted by 67% (respndents=20) rganizatinal unit. The usage f lean sftware develpment methds wuld be help said by 67% because they agreed n abut mre than 50% benefits f lean. And left were nt agreed r nt sure and thse were abut 33%. Number f respndents wh were accepted quality attributes abut Lean Scrum Mdel shwn in Table 1 where A is number f respndents wh were accepted that quality attributes abut lean. The graph als displayed which shws their level f acceptance. Table I: N f respndents wh were accepted quality attributes abut Lean Scrum Mdel Lean benefits Descriptin A B1 Lean Principles in Scrum develpment reduce the develper verlad 17 B2 Build quality int the cde frm the start take less time f sftware develpment 13 B3 Lean principles have acted as stabilizing mediatr in scrum practice 14 B4 Decisin will be made late lead t less taken f wrng decisin 16 B5 Cmbining lean and agile with scrum mdel methdlgy imprve scrum methdlgy 14 Rati between Agreed/Disagreed Disagreed 33% Agreed 67% Figure 4: Rati between Agreed/Disagreed Fig.4 shws rati between agree and disagree abut Lean Scrum benefits. ISSN : Vl. 21 N. 2, Apr

9 Cmbining Agile Mdel with Lean Principles t Imprve Scrum Mdel Methdlgy in Sftware Cmpanies Figure 5: Benefits by using lean principles and agile Mdel with scrum practice Fig.5 shws the benefits by using lean principles and Agile practice. Different rganizatin shws prductivity and quality enhanced with the prpsed mdel. Figure 6: Lean principles value accrding t respndent Fig.6 represents lean principles value accrding t respndents in sftware develpment prcess. ISSN : Vl. 21 N. 2, Apr

10 Gul Naz and Nayyar Iqbal 6 CONCLUSION AND FUTURE WORK The current trend in sftware develpment pints twards the cmbinatin f Lean thinking and ASD, after success in manufacturing prcess lean becmes mst imprtant part f sftware develpment. Hwever, the bdy f knwledge n this tpic is limited. This research frmulated a prcess mdel by cmbining apprpriate Lean principles with the agile prcess mdel t minimize the scrum issues and imprved the scrum prcess certainty, prductivity and stability. Lean thinking pens up a spacius variety f pprtunities fr advance research. The challenges recgnized when mving twards a cmbinatin f Lean and ASD particularly advantage required further study. REFERENCES [1] Pressman, Sftware Engineering a Practiner s Apprach. New Yrk, NY: McGraw-Hill educatin. pp , [2] Middletn, P. and D. Jyce, Lean Sftware Management: BBC Wrldwide Case Study. IEEE Transactins n Engineering Management, vl.59, n. 1, pp [3] Wang, X. Cnby, K. And O. Cawley, Leagile sftware develpment: An experience reprt analysis f the applicatin f lean appraches in agile sftware develpment. Jurnal f Systems Sftware vl.85, n. 6, pp [4] Balachander, A and A. Harris, A. Lessns in lean [lean manufacturing]. Manufacturing Engineer.vl.83, n. 5, pp [5] Ali, A. M. Survey n the State f Agile Practices Implementatin in Pakistan. Internatinal Jurnal f Infrmatin and Cmmunicatin Technlgy Research, vl. 2, n. 5, pp , [6] Ahmad, M., J. Markkula and M. Oiv. Kanban in sftware develpment: A systematic literature review. Prceedings f the 39th Eurmicr Cnference series n Sftware Engineering and Advanced Applicatins (SEAA) Santander, Spain, pp [7] Jnssn, H., S. Larssn and S. Punnekkat, Synthesizing a Cmprehensive Framewrk fr Lean Sftware Develpment. Sftware Engineering and Advanced Applicatins (SEAA). pp [8] Rdríguez P, Partanen J, Kuvaja P &Oiv M (2014) Cmbining lean thinking and agile methds fr sftware develpment. A case study f Finnish prvider f wireless embedded systems. Prceedings f the 47 th Hawaii Internatinal Cnference n Systems Sciences (HICSS 2014). In press. [9] Leffingwell, D. Scaling sftware agility: Best practices fr large enterprises.1 st Ed [10] Agile Manifest (2001) Beck K, Beedle M, van Bennekum A, Cckburn A, Cunningha, W.,Fwler M, Grenning J, Highsmith J, Hunt A, Jeffries R, Kern J, Marick B, Martin RC, Mellr S, Schwaber K, Sutherland J & Thmas D Manifest fr Agile Sftware Develpment, [11] Schwaber, K., and M. Beedle. Agile sftware develpment with Scrum, Upper Saddle River, NJ: Prentice Hall.pp [12] Pppendieck, M. & Cusuman, M.A., Lean Sftware Develpment: A Tutrial. IEEE Cmputer Sciety [13] Y. Matsui, An empirical analysis f just-in-time prductin in Japanese manufacturing cmpanies, Internatinal Jurnal f Prductin ecnmics, vl. 108, n. 1-2, pp , [14] Wmack, J.P., Jnes, D.T, Lean Thinking: Banish Waste and Create Wealth in Yur Crpratin, Simn & Schuster, New Yrk ISSN : Vl. 21 N. 2, Apr