INTERNATIONAL DESIGN CONFERENCE – DESIGN 2020 MEETS PLAN-DRIVEN – HYBRID APPROACHES IN PRODUCTDEVELOPMENT: A SYSTEMATIC LITERATURE REVIEWJ. Heimicke , R. Chen and A. AlbersKarlsruhe Institute of Technology, [email protected] than 15 years after the publication of the agile manifesto of software development, agiledevelopment approaches have also reached the processes of physical product development.Because of the boundary conditions and requirements here, which differ strongly from those ofpure software development, these approaches often reach their limits. However, research andpractice have quickly recognized that hybrid approaches integrate the strengths of agile and plandriven development. This paper presents 25 hybrid development approaches that have beenidentified in a Systematic Literature Review.Keywords: product development, design process, engineering design, agile product development,hybrid development approaches1. IntroductionThe integration of agile and traditional development is gaining more and more attention for a varietyof reasons. In the development of mechatronic products, the proportion of the three major engineeringsciences involved - mechanical engineering, electrical engineering, and computer science - are roughlyequal. As an interdisciplinary product development, to better meet customer requirements, thedisciplines in various fields should be further integrated. (Neumann, 2012) In order to meet therequirements of interdisciplinarity in development, companies used to adopt some traditionaldevelopment models, such as V-model. However, to thoroughly consider changing markets, variablecustomer requirements, the Internet of Things, and many other challenges, companies use newapproaches - agile approaches - in development. (Schmidt et al., 2019) Although many companies arestill implementing agile methods, (Goevert et al., 2019) some companies have noticed that pure agilemethods in mechatronics system development have reached their limits (for example, the followingshortcomings: lack of necessary documents; measuring the progress of the entire project is difficult).(Heimicke et al., 2019) For this reason, they often combine agile and traditional approaches. Forinstance, Cooper and Sommer (2018) found that today’s gated process is too rigid, and an overly strictdevelopment model makes the development process less active and slow to respond. But markets andtechnologies are getting faster and faster, and there are global factors. Companies must releaseproducts and bring them to the market in a short period. Product development is more challenging thanbefore. They built a hybrid model - Agile-Stage-Gate - that has the advantages of both the structureand control of the stage-and-gate system and the speed and productivity of the agile method. (Cooperand Sommer, 2018) Furthermore, Hybrid Development Approaches (HDA) aim to choose a processDESIGN ORGANISATION AND MANAGEMENT577

model to fit best a product development project, which is also possible to do this on a higher level ofdetail. (Schuh et al., 2018) As mentioned earlier, there are advantages and disadvantages to agiledevelopment and traditional methods. Some researchers and some companies have realized that thehybrid method created by combining the two is a feasible way. The hybrid development approach hasgreat prospects and potential in the mechatronics industry. However, as the number of hybridapproaches continues to rise, there is no comprehensive interpretation of the various developmentapproaches, such as composition, development framework, and practical examples. This is the mainreason for our literature review to further develop hybrid methods with specific applications indifferent environments, and we need to better understand its composition, development framework,and practical examples. The purpose of this article is to lay the foundation to further hybriddevelopment methods through a literature review that describes the main attributes of hybriddevelopment and studies the advantages and challenges of these methods. In this way, we provide anoverview of the current state of research in the field of hybrid development approaches. Theunderstanding created in this way enables the further development of the situation- and demandoriented use of suitable development approaches in later research work.2. Plan-driven and agile developmentNew product development is the source of competitive advantage for enterprises and the basis forthe continuous growth of corporate profits. (Schumpeter, 1912) In this fast-changing era, industrialcompanies, from the assumption of the user’s needs to the official production of the product to themarket, which goes through many stages, involving a wide range of technical fields and many steps,so it must work according to specified procedures. To support developers in the productdevelopment process, a distinction is made between traditional or plan-driven procedures and agileprocedures. Plan-driven methods include, besides others, the Waterfall model or the V model. Theircharacteristics are distinguished based on different development stages. The waterfall model is oneof the most commonly used development methods. It is a linear structure, which means that only theprevious phase be ultimately ended, and the next phase begins. It is characterized by simplicity andease of management. Users can only see development results when they wait until the end of theprocess, which increases development risk through undetected errors that were made early in theprocess and have significant late effects. Traditional plan-driven models can be better applied tolarge projects. Strategies, documents, and processes can contribute to a better connection andcoordination among large organizations. (Boehm and Turner, 2004) At the same time, agiledevelopment is a lightweight development that uses short-term iterations to engage users in projectsactively, validate and prioritize requirements. Real agile development must be iterative, incremental,self-organizing, and emergent. This means that the project can take several cycles to complete, andeach cycle delivers semi-finished products until it is completed. The team manages work mostcompetently, and the process, principle, and work structure are determined during the project, ratherthan being pre-set at the outset. (Boehm and Turner, 2005) In mechatronic system development,agility is particularly apparent as the ability of a development team to adapt the phases of synthesisand analysis reactively and purposefully to changes in the development context. (Albers et al.,2019a) A variety of factors can distinguish agile development and plan-driven development. Agiledevelopment is designed for small development teams, close communication within the team,collaboration between developers and customers, continuous delivery of available samples in a shortperiod, and optimization of products based on customer feedback. The plan-driven developmentrelies on clear steps and terms. Its core lies in the definition and management of the process. Theadvantage is the repeatability brought by the standardized steps and the stability in the developmentprocess. It is suitable for large-scale team development projects based on customer requirements.(Boehm and Turner, 2004) Common Approaches of Agile Development are Scrum, eXtremeProgramming and Kanban. Scrum is a framework for developing and maintaining complexproducts. It is an incremental, iterative development process. In this framework, the entiredevelopment process consists of several short iteration cycles. A short iteration cycle is called aSprint, and the recommended length of each Sprint is 2 to 4 weeks (1-week Sprint can be used forInternet product development). In Scrum, the product backlog is used to manage the requirements of578DESIGN ORGANISATION AND MANAGEMENT

the product. The product backlog is a list of requirements sorted by business value. Themanifestation of the list entry is usually a user story. Extreme Programming focuses on specificengineering practices. XP is designed to enable developers to respond confidently to customer needsthrough a reasonable mix of engineering practices. Emphasize the feedback loop mechanism, thefeedback loop between the customer and the R & D team, the feedback loop for testing anddevelopment, and the feedback loop between specific code implementation and unit testing. Kanbancomes from visual signals or cards in Japanese. Toyota uses Kanban to control the productionprocess. During the entire production process, these cards will be accompanied by separatematerials, and the cards will send corresponding signals at different stages of production, indicatingthat this work step has been completed. However, the number of cards is limited, which can avoidproduction bottlenecks. If all cards are in use, new work cannot begin until the cards havecompleted the entire production process and are available again. (Saleh et al., 2019)3. Research approachHybrid approaches in product development combine the strengths of agile and plan-driven approaches.However, there is currently no overview and analysis of existing hybrid approaches. In order to createa basis for further research on hybrid approaches in product development, the following researchquestions are answered in this paper:RQ1: Which hybrid approaches to product development exist in the literature? What are theirbasic principles?RQ2: What are the benefits of adopting Hybrid Development Approaches for the developmentprocess?The method used in this research is the Systematic Literature Review (SLR). It was conducted inaccordance with the guidelines provided by Kitchenham and Charters (2007). This guide covers themain steps of the literature review: identifying goals, defining methods, document collection, collatingliterature, researching features, and analysing results. (Kitchenham and Charters, 2007)3.1. Data sourcesIn this paper, we searched in the following digital libraries and databases: Scopus und Web of Science(WoS). The reason why these two databases are selected is the following three points. According toBauschmann and Ahnert (2017), WoS has some advantages, for example, deep development,improved regional coverage, self-citation can be excluded. Scopus is even more comprehensive thanWoS. (Bauschmann and Ahnert, 2017) In order to get more inclusive data, we chose to search in both.Based on our research questions, we used the following string in both libraries.(hybrid OR tailored) AND (hardware OR mechatronic OR software AND planning OR developmentOR process*) AND (agile OR waterfall OR plan-driven).3.2. Inclusion and exclusion criteriaWe aim at identifying papers that propose a method combining agile with traditional developmentmethods, or the integration of an agile approach in the plan-driven development process. Besides, onlyEnglish and peer-reviewed papers are included, and only one of several versions is retained. Thefollowing type of publications are excluded: papers proposing agile methods with a focus on Irrelevantcontent, articles offering approaches for the hybrid method with only Case Studies, papers proposingstrategies for a hybrid method without addressing product development (e.g., hybrid material).3.3. Data extractionThe search string obtains from SCOPUS and WOS, provides us with 1,628 articles. In Figure 1. weillustrate the selection process. The first step is to filter out the chapters in the book or book from theresults obtained, and we get 1478 articles. The second step is to filter out the duplicates, and now thereare 1445 contributions left. The third step is done by reading the title and abstract. Chose whether tocontinue reading the full documentation based on the exclusion criteria.DESIGN ORGANISATION AND MANAGEMENT579

1628 documentsScopus: 963 document results WoS: 665 document resultsBook and book chapterExclude1478 documentsFilter for duplicates1445 documentsFilter for Abstracts101 documentsFigure 1. Selection process of the conducted Systematic Literature Review4. ResultsBased on the contents of the title and abstract, 101 contributions remained. We have analysed these andidentified 25 significantly divergent hybrid approaches which are presented in Table 1. In addition to thecore idea (column 3) of the respective approach, the second column shows the elements used to form thenew approach. The original source is shown in the fourth column. Table 1 shows the central result of theresearch work. In addition, we show an excerpt from our analysis of hybrid approaches with regard to theirbenefits. Here is a brief introduction to the following several important methods of agile development.Distribution of Papers: When investigating the result set, it became obvious that, while the HybridDevelopment Approaches were first discussed in 2007 (User-centered agile), the topic gainedmomentum in 2014 and, since then, a continually high number of relevant articles have been publishedevery year. This reflects that, while the idea of integrating traditional and agile development has beenaround for some time, integration problems are still unconcluded and investigation is continuing.Table 1. Overview of Hybrid Development Approaches in this SLRApproaches and Main IdeasElementsSourceNo.Agent Agile Game Development methodology: The suggested methodologyDaily Scrum (Al-Azawi et A1al., 2014)AAGDM combines agile methodology that meets the dynamic requirements of theSprintcustomer with Multi Agent Software Engineering (MaSE). The MaSE used in theMaSESprint phase is at the core of the AAGDM.Agile & JAD: In this paper, they are providing a hybrid approach for requirement Daily Scrum (Kumar et al., A22014)engineering in the agile with the help of Joint Application Development (JAD) andJADthe prioritization of the requirements in the agile is helped by the viewpoint.Agile Model Driven can optimize software development, the most important is the Model Driven (Zhang and A3Patel, 2010)higher yields and better-quality code. Second, more communication withSprintscustomers during the development process. Its life development cycle is dividedDaily Scruminto three consecutive iterations.Agile Product Line Engineering: AgiFPL is designed to increase agility withinthe PLE and effectively meet any emerging business expectations. On the onehand, for the Domain Engineering phase, AgiFPL implements an iterative processthat uses the i* method with Scrumban. On the other hand, for the ApplicationEngineering phase, AgiFPL also implements an iterative process that uses theScrum method in conjunction with i*. Each process of AgiFPL is based oniterative and incremental development.Daily Scrum (Haidar et al., A42017)Product LineEngineeringAgile-Stage-Gate combines classic stage-gate and agile. The stage-gate processstructure (stage and gate) and short-cycle iteration of agile development aredesigned to improve communication, quick feedback on customer needs, andhigher productivity. And make development activities no longer isolated.Stage-Gate (Cooper and A5Sommer,Daily Scrum2018)Sprints580DESIGN ORGANISATION AND MANAGEMENT

Agile-Waterfall: Water defines the upfront work. Teams use scrum to developsoftware in the middle of the process. Fall means establishing gates to limitsoftware release frequency.AI techniques & Agile: The model is made up of three layers: RUP layer,integrated Scrum layer and CBR (Case Based Reasoning) layer. Common CBR isan AI technique that emphasizes the memorization of prior cases. In the first place,the main RUP layer is founded on the overall values of a unified process (UP),which include cycle tracking, stakeholder preferences, team collaboration,repeatable validation, and stress on quality and fostering the level of detail. In thesecond place, the Scrum layer is merged with the fundamental RNP steps, namely:inception, elaboration, construction and transition. CBR is linked to the Scrumactivities. The vision in shape of a use case diagram of the Unified ModelingLanguage (UML) is stored in CBR in the form of a case. Likewise, the deliverablesand the solution are stored in CBR at the end, which can be used again in the futurewhen the same shape of the vision occurs.Competitor Driven Development & Extreme programming: Reverseengineering of competitor products was applied. List down all the better andattractive features present in it to incorporate them in our product. Test-Firstpractice of XP ensures that the code is properly tested for functioning correctly.Design thinking & Extreme programming: The several Design thinkingpractices are adapted into two XP phases called the investigation and plan phase. DT integration in XP exploration phase (Empathy, Define, User persona, DT-userstories); DT integration in XP planning phase (Automated prototyping, Prototypeusability evaluation, Usability, User testing)Enterprise Architecture Management & Agile: This theory aims to use agilemethods in EA management. Roles, duration, activities, and expected results areborrowed directly from Scrum. Map Scrum concepts (sprints, requirements, userstories) into EA management.Global Software development & Agile: They suggest incremental integration,short iterations, regular short status meetings, various communication modes,customer representatives in offshore teams. Basic agile principles ofcommunication mechanism, frequent deliveries are suggested to improve customertrust and relationship and bridge the gaps in coordination and also overcomecultural differences.Human Centered Design & Agile: User exploratory research is conducted at thebeginning of development. Sprints have a fixed duration of 1 week. Each sprintbegins and ends with a re-estimation and evaluation.Waterfall(West, 2011) A6Daily ScrumDaily ScrumAI technique(Mukhtar etal., 2013)A7XPFDRD(Doshi andPatil, 2016)A8XPDesignthinking(Sohaib et al., A92019)Daily Scrum (Hanschke et A10al., 2015)EAMGlobal(Ivček and A11SoftwareGalinacdevelopment Grbac, 2008)SprintHumanCenteredDesignTRIZScrum(Ardito et al., A122017)Inventive Problem Solving & Agile: They are integrating project-level(Fulbright,innovations of so-called invention problem solutions into agile methods such as2013)Scrum, transforming development teams to leverage their expertise in informationtechnology to influence the overall solution architecture to maximize profits. As aresult, innovative and efficient solutions are recommended and implemented.LEAN & Agile: This paper proposes a production control system built on lean andLEAN(Takahashi etagile strategies to react to changes in the composition of the product mix byal., 2007)reassigning work elements in each workstation. Performance is analyzed underconditions of volatile changes in the product mix by experimental simulation.Lean six sigma & agile: This article combines six sigma, lean and agileLean six sigma (Badwe anddevelopment. Lean development and six sigma focus on performanceErkan, 2018)improvement, and agile development focuses on rapid development. Theircombination helps to quickly deliver high performance products to customers.Product family modelling & Agile: This paper describes structural modelingSoftware(Raatikainenusing two methods (called Kumbang and Agilefant). The integration aims towardsProductet al., 2008)advancing product development governance by contributing technology in terms ofFamilyconcepts and even automated tool support for preparation, monitoring, andEngineeringcommanding the development activity for various stakeholders.A13DESIGN ORGANISATION AND MANAGEMENT581A14A15A16

Quantitative Scheduling & Agile: They combine mathematical programmingDaily Scrumwith agile development. This method can be used to generate schedules as aQuantitativebenchmark for agile iterative development. This approach is an effectiveSchedulingcomplement to agile project management, especially if the budget is limited.Rational Unified Professing & Agile: In proposed hybrid approach, 9 RUPRationaldisciplines have been reduced to 7 disciplines after considering suitable mappingUnifiedwith Scrum. The disciplines utilization in each phase may be different forProfessingiterations. Sprint plan meeting, daily scrum meeting and sprint review meeting caneasily be embedded into elaboration and construction phases. Each sprint boostswith a sprint plan meeting and finalizes with the sprint review meeting.Risk Management & Agile: This paper proposes a risk management model thatRiskcan be applied to the agile development process. This model defines securityManagementrequirements, high-risk feature lists, identification functions, response functions,and monitoring functions. The model revolves around a risk board that is used andupdated throughout the software development cycle.Scrumban is a mix of scrum and Kanban. It can improve the applicability andKanbanversatility of product manufacturing and support the companies that care. ThisDaily Scrummethod is mainly used for fast start-up of dynamic environments.User-storiesScrumconix uses the project managing framework of Scrum, and part of theDaily Scrumsoftware engineering guide of ICONIX. It is basically composed of two parts:SprintSprint Zero and Sprint One to N. Sprint Zero includes the following points: OverallICONIXrequirements gathering; Domain and use case modelling; Reference softwarearchitecture; Overall project estimation; GUIs refinement; Sprint planning. TheScrum activities are unchanged.Security & Agile: Security assessments have been added to each of the agileSec. backprocesses to ensure security without changing the agility.logSEMP& Agile: A Systems Engineering Management Plan is a managementDaily Scrummethod for contractors’ systems engineering. A new hybrid approach thatSEMPcombines the principles of agility with the principle of SEMP to define the mostcritical role of the Product Owner (PO). He/she should understand the needs andexpectations of the customer, understand the technical terminology, and be able tomake individual decisions simultaneously. The development team is implementedin a similar way to the standard agile method.User-centered agile: The integration of User-centered design (UCD) and agile isDaily Scrummainly in the following parts: Little Design Up Front; Prototyping; User Stories;DemoUser testing; Inspection evaluation; One sprint ahead. This combination is basedUser-centeredon the following principles: Separate Product Discovery and Product Creation;designIterative and Incremental Design and Development; Parallel Interwoven CreationTracks; Continuous Stakeholder Involvement; Artifact-Mediated Communication.XP & Throwaway Prototyping: Need to build a GUI prototype. The GUIXPprototype will be used for the final system. If the end-users are not satisfied withThrowawaythe GUI, the developers will go back to the analysis, design and implementationPrototypingphase to come out with a new GUI and the process goes on and on until they aresatisfied.(Jahr, 2014) A17(Tanveer,2016)A18(Ylimannela, A192013)(Matthies,2018)A20(Portela and A21Borrego,2016)(Ghani et al., A222014)(Lom et al., A232016)(Aguilar and A24Zapata, 2017)(Alqudah and A25Abdulsalam,2013)The Process of Hybrid Development Approaches: We found that most of the reviewed HybridDevelopment Approaches were based on traditional development methods. That maybe sinceconventional development methods can be considered as a stable process, but practitioners maintainthat this stability will make the development process rigid. Introducing agility to the processes isintended to make those processes more flexible. Scrum and Extreme Programming are the mostusually used agile elements that were integrated into traditional methods. These outcomes are notextraordinary, since surveys dealing with agile approaches recognized Scrum and ExtremeProgramming as the most popular agile elements. However, regarding some Hybrid DevelopmentApproaches it was not specified which agile methods were used. The most common benefit of agiledevelopment is that customers can quickly see a prototype of a product and a validation can be made,because Scrum focuses on managing iterative development, and Extreme Programming focuses onincremental progress. Both bring higher productivity. Other purposes are optimizations for agile582DESIGN ORGANISATION AND MANAGEMENT

development, such as reduce risk during the development process. Another example is establishingcatalogue management for agile development because agile development focuses on thecommunication within teams but ignores the importance of documents. Agile development isgenerally considered to be suitable for small teams or small projects. To make its application moreextensive, some articles propose optimization methods that can be applied to, for example, globaldevelopment, or large projects and multinational corporation.The Aims of Hybrid Development Approaches: Keeping the customer involved and activelycollaborated in the development process, is most often mentioned aim. Next is trying to improve thecost-efficiency of the project and then accelerating development process. There are some other ones,like increases adaptability and universality for product manufacturing.The Application Domain: The most familiar domain for Hybrid Development Approaches wasSoftware development. Other fields include Manufacturing, web applications, game development, andtelecommunication. The most of approaches were targeting a single domain. Nevertheless, few studiesexplicitly stated that they could be implemented more-ordinarily for large size projects such as A18.5. Benefits and challenges of the identified approachesWithin the identified contributions, the benefits of combining plan-driven and agile approaches werereported in many aspects. Figure 2 displays the coverage of hybrid approaches with regard to theadvantages identified by Schmidt et al. (2019) that companies hope to gain from integrating agileelements into their processes. It was found that only the approaches marked in bold were sufficientlyempirical to make robust statements about the benefits of the approaches. For the remainingapproaches, the classification is based on the literature - which in turn is partly based on assumptions.Figure 2. Overview of the benefits of Hybrid Development ApproachesDESIGN ORGANISATION AND MANAGEMENT583

We made the assignment on the basis of the identified literature. Besides the aspect, that it is difficult toquantify the communication improvements which came from the adoption of the respective hybridmodel this benefit is one of the most discussed. A3, A5, A9, A11, A18, A21, A23, and A24 all claim thatcommunication in the team has improved because of the agile elements. A5 assumes that excellent teamcommunication will bring more control and better management of project progress. A11 mentioned thatone of the biggest problems facing global multinational companies in the software development processis the communication of staff in different regions. Agile development practices have received a lot ofattention for their flexibility, this remarkable feature has also been retained in A5, A6, A10, A12 andA24. A5 explains this in the way that the development should be based on early feedback fromcustomers and on important product features, rather than focus working on rigid plans. A24 supposesthat agile can enhance UCD through higher frequency usability assessments, enabling customers’ earlyfeedback to be better integrated into the product. In terms of productivity, A3 noticed a threefoldincrease in code output. Similar to that aspect, A15 observed an improvement in productivity. Here itwas based on the shorter turnaround times due to continuous focus on the deliverables. A3, A11, A14,A20 and A22 mentioned reducing the risk in the project. For example, A22 defines bad behaviour andrisk, and what measures can be taken to reduce these risks. A1, A3, A9, A12, A14, A18, A20, and A22highlighted that the time to market for the product has been shortened.Articles containing the following hybrid approaches mention their problems. A3 mentioned that, lackof understanding in middle or top management and isolation of agile teams from the rest oforganization are the most common challenges they find. A20 mentions that agile development canaccept quick feedback from customers to guarantee that valuable products are implemented as quicklyas possible. But the agile development team’s company does not have a flexible and dynamicstructure. Instead, they mostly have cumbersome processes. Adopting agile development does notchange the underlying corporate structure of the company itself. Many articles have this assumption,and all work is based on a short-cycle form of a small self-organizing team. This means that the usageof hybrid development in large companies or large projects is also a huge challenge. There are alsoseveral common challenges as described following: Frequent customer feedback request, conditionalsuitability for distributed development and chaotic approach in the project.6. Discussion & conclusionIn this paper, we have presented details of a Systematic Literature Review on Hybrid DevelopmentApproaches. In total we have identified 1628 contributions by a search string and reduced them by theSystematic Literature Review to 101 papers published between 2003 and 2019. The main characteristicsof Hybrid Development Approaches were investigated, and the observed benefits identified. The resultsshow that there is still much confusion about what Hybrid Development Approaches are and how thetwo different approaches of agile and plan-driven development can be effectively integrated. While theresearch method used enabled us to identify 25 different approaches that are the result of a combinationof agile and plan-driven development, we must admit that we could only find literature that explicitlyaimed to create a hybrid development approach

AGILE MEETS PLAN-DRIVEN – HYBRID APPROACHES IN PRODUCT DEVELOPMENT: A SYSTEMATIC LITERATURE REVIEW J. Heimicke , R. Chen and A. Albers Karlsruhe Institute of Technology, Germany [email protected] Abstract More than 15 years after the publication of the agile