Systematic Literature Review of Trend and Characteristic Agile Model

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INTRODUCTION
Every engineer requires a so-called process model when developing software. The software development process is abstracted in the software process model. The stages and order of each process are established by this process model. Process models are constantly evolving with the times, and the Agile Model is one of the process models that has evolved into a container for many other process models.
Throughout the course of a project's lifespan, repetitive and incremental interactions are made as part of the agile conceptual framework for software engineering, which starts with the initial planning phase and continues until the deployment phase. The agile method's major objective is to reduce additional spending on software development while allowing for change without endangering the procedure or causing overwork [1].
It is not surprising that numerous researchers have raised research on agile approaches given the dependability they offer. According to studies by Aftab et al. [2] between Extreme Programming (XP) and the Feature Driven Development (FDD) approach. This study examines a number of indicators, including productivity, actual work effort, and design classes. According to the study's findings, FDD performs poorly when compared to XP in practically every significant statistic. Due to extensive development, challenging projects, and communication issues, FDD is made worse. However, this study claims that the FDD's heavy, inflexible structure and intricacy are its two most important factors.
Additionally, Puttida et al. [3] employing the scrum approach to research. This study uses the scrum method to evaluate team performance. According to the study's findings, the scrum methodology may be used to implement product management and working methods, enabling teams, products, and working conditions to be continuously improved. Additionally, this study explains how several elements, like bravery, commitment, focus, openness, and respect, have an impact on the effectiveness of the scrum technique.
In 2021, research employing the FDD approach will be conducted once more. This Research [4], In order to help the disaster response team conduct assessments in the impacted areas more efficiently and promptly, we must study and design a disaster emergency response assessment system. The investigation's finding is that larger and more significant software projects can use the FDD method. Consequently, it is anticipated that this research will be able to give advice that is pertinent to and in line with Indonesian laws and regulations.
There are several forms of agile methodologies besides those already mentioned, including Scrum Methodology, Scaled Agile Framework, Lean Software Development, Kanban, Extreme Programming (XP), Crystal Methodology, Dynamic Systems Development (DSDM), and Feature Driven Development (FDD). Each methodology has its own guiding principles, life cycle, constituent parts, benefits, and drawbacks. Therefore, before choosing to employ one of these methods, every engineer and researcher needs to be aware of its qualities and properties.
In order to make it simpler for researchers and engineers to decide which technique is best to employ on the project at hand, this study gives information regarding trend studies in agile methods as well as the characteristics of each agile approach. In order to determine whether the method is updated annually, articles from the last eight years, from 2018 to 2022, were gathered for this study.

LITERATURE REVIEW
An incremental approach to project software development is prioritized by agile software development in project management surpasses the specified phase [5]. This approach places a strong emphasis on three things: (i) ongoing software testing; (ii) collaboration between developers and consumers; and (iii) the human element of software development, which goes beyond methods and tools.
Software development operations can be made better and faster by integrating quality practices and systems that track benefits. This will raise customer satisfaction levels [6]. Agile Software Development enables firms to respond quickly to ongoing changes in business conditions because of this, with an emphasis on flexibility in the face of uncertainty and ongoing change. The most popular Agile Methodology techniques are listed below: a. Scaled Agile Framework Dean Leffigwell created the Scaled Agile Framework to modernize agile for large businesses [7]. The success that its customers have had in achieving enterprise-wide success has lately helped the Scaled Agile Framework gain widespread recognition. By integrating SAFe across the entire organization, other Agile methodologies like Scrum, Extreme Programming, test-driven programming, team focus, and project-level practices are improved. The Scaled Agile Framework (SAFe) methodology was created to aid big businesses in producing high-quality products more quickly and affordably while also increasing user happiness [8]. According to [9] SAFe in terms of human resources and project management practices is quite demanding and costly to implement SAFe, companies need to commit the time and resources they have and need for this method to be adopted properly. the individuals involved also need to receive specific attention and training so that this method can work effectively and deliver the best results.
It blends Scrum, Extreme Programming, Kanban, and Lean techniques at the team level. Value stream, program, portfolio, and team levels are available. Built-in quality, transparency, alignment, and program execution are the basic values of SAFe. Kanban Kanban is a method for displaying a manufacturing system's process. By focusing on the flow of production, Kanban employs queuing theory to regulate and enhance the flow of value. David Anderson, working with the Microsoft software team, introduced Kanban to software engineering for the first time in 2004. Anderson lists these five guiding concepts for Kanban: Create specific process policies, visualize workflows, limit work-in-progress, measure and monitor flow, restrict work-inprogress, use models to find expanding opportunities [10].
Implementing kanban can help businesses satisfy customer demands and coordinate multiple products by reducing overproduction. Kanban is useful for fostering both continuous improvement and overall production support. With Kanban, cycle times are shortened since the focus is on minimizing active development activity and visualizing the flow of development value [11], [12].
In practice, Kanban provides great flexibility and can be adapted very well to projects that have different needs and characteristics, for the success of kanban, a deep understanding of kanban principles and practices is required, as well as the participation of all members [13] .

Figure 2. Workflow of Kanban
According to research [14], The least prescriptive agile methodology is kanban, which only adds restrictions related to visualizing the workflow and limiting work in progress. c.
Scrum Scrum is a structured Agile methodology used for solving challenging problems in product development [15]. Scrum is intended to accelerate development, harmonize personal and organizational goals, and improve individual growth and quality. Although it is not always employed, the agile method known as Scrum has grown in popularity recently and is proving effective for software development [16].
In Scrum, there are three roles: Product Owner, Development Team, and Scrum Master [17]. The product owner is in charge of determining the plan as a product backlog. The development team is responsible for implementing the plans from the product backlog. The Scrum Master plays an important role in the entire Scrum process that occurs and ensures that all members of the developer are responsible for the entire process.
Scrum includes benefits like variable sprint requirement selection and no set procedures to follow, and it allows a tailored approach of working on various projects with varying requirements [1]. Despite being widely utilized, scrum still has a few key advantages over other approaches [18].
Scrum has proven to be effective for increasing productivity, transparency and engagement of each team member. Scrum's flexibility allows for good implementation in complex projects and changing environments [19]. Krafcik (1988) first used the term "lean" to refer to the Toyota Production System's operating procedure. Lean has four main methods: (1) Transparency; (2) Standardization and optimization; (3) Leading by key performance indicators (KPI) (4) Organizational culture [20]. In practice, lean has a positive impact on processes. Lean implementation can help increase efficiency, reduce waste, and improve accuracy in process execution. lean focuses on identifying and eliminating waste that occurs in processes thereby increasing productivity and effectiveness. companies/organizations that implement lean practices consistently and continuously have a better chance of achieving higher levels of process quality [21]. e.

Extreme Programming
The most popular and widely adopted Agile methodology is called "Extreme Programming" (XP), which emphasizes the virtues of "simplicity, communication, effective feedback, and courage to face hurdles". This method delivers superior quality products while satisfying customers, made in small teams and team members who value collaboration [22].
With XP, work is intended to begin with a smaller development team and fewer detail artifacts. The development cycle of XP uses an iterative and vertical methodology. The four fundamental XP principles for software development are planning, coding, designing, and testing [12], [23]. Crystal split into four labels: white, yellow, orange, and red. The more colors, the deeper and more difficult the problem [12], [24]. The crystal method emphasizes adaptability and flexibility in software development. Crystal can help improve project performance by considering the unique needs of each project. This method emphasizes the importance of communication and collaboration between team members in the project [25]. It is an iterative and incremental technique that unifies the project and product management life cycles into a single process [26]. Because DSDM focuses on strategic goals while managing time, money, risk, and quality, it has been demonstrated that it may assist deliver outcomes efficiently and rapidly. However, in practice, not all projects-such as those that are real-time or safety-critical-are appropriate for adopting DSDM [27].

Figure 6. Workflow of DSDM
In practice, DSDM may present obstacles and hurdles, such as a lack of understanding and awareness of DSDM, a lack of stakeholder involvement, and difficulties in managing rapid change. For this reason, in practice, DSDM needs strong management support, appropriate training, effective communication between team members and interested parties, and an organizational culture that supports agile practices [28]. h.
Feature Driven Development Peter Coad and colleagues created the concept of feature driven development in 1999, and Palmer and colleagues improved it in 2002 [29]. Large and complicated projects frequently adopt the agile paradigm known as "Feature Driven Development" (FDD) [2]. The five stages of FDD are: developing the overall model; building the feature; planning and designing by feature; and building by feature. FDD, on the other hand, concentrates on the design and development stages before emphasizing quality factors all across the process by meticulously tracking each process's development. Because each FDD process involves a number of activities and responsibilities, it depends on the developer's experience and is strict in its execution, making it only appropriate for usage on medium-to large-scale projects.

Figure 7. Workflow FDD
In practice, FDD takes a structured and systematic approach to identifying, planning and implementing key features. FDD implementation uses object oriented modeling which is key to FDD success. FDD is suitable for projects that have high complexity and require a clearly organized structure. FDD is relatively easy to understand and implement, making it suitable for learning approaches in educational contexts [30].

Research Question
A systematic literature review is a task that involves finding, assessing, and interpreting pertinent research utilizing a query connected to intriguing subjects and interesting phenomena to watch [15]. Therefore, it is essential to provide a study topic to guide what will serve as the emphasis for resolving the issues discovered.
The study's research questions are RQ1. What has been the recent trend in studies utilizing agile techniques in the last 8 years? RQ2. What are the characteristics of each process model in agile methods??

Library Initiation and Selection
The method of searching for literature reviews that will be used to respond to the research question is ; a. Choose keywords. Agile, Scale Agile Framework, Kanban, Scrum, Lean, Xtreme Programming Crystal, and Dynamic System Development Method were the keywords employed in this study's literature search. b. The publish or perish 8 application was utilized as the data source to get the literature. Additionally, it makes use of a number of websites, including Google Scholar, IEEE Xplore, Springer, Elsevier, ACM Digital Library, and related publications.

Inclusion and Exclusion Criteria
Inclusion criteria are criteria used to identify existing subjects in existing research to later be included in the research to be done [20]. Criteria that are used as a cue in one or more scholarly journal articles, conference papers, and journal articles. The exclusive criteria are the study topics that don't relate to the active research topics. Here are some hints and details found in this literary work:

Data Extraction
Data extraction is done in order to take into account the restrictions on the types of data that will be examined in a systematic literature review. The following data were extracted for this study: 1. Title 2.
Year 3. Type of Publisher 4. Process Model used 5. Characteristics

RESULT AND DISCUSSION
The important difference that exists between the use of the agile method and the traditional method lies in the adjustment of the criteria for the project to be worked on, where software development with the agile method is carried out by considering various things that suit the needs of the user. In the agile method, software development does not immediately produce a design until the end of the system, but gradually, according to the method you want to use. Each method will make a design to find out the errors and deficiencies of the development process. Developers will also adapt to the topics or ideas that users want and in what areas the software will be applied. as in the study conducted by Aftab et al. [2], who compared productivity, actual work effort, and design class of XP with FDD. The study found that FDD performed poorly when compared to XP in almost every significant statistic due to its heavy and inflexible structure and complexity.
Another study conducted by Puttida et al. [3] using the Scrum approach to evaluate team performance found that the Scrum methodology can be used to implement product management and work methods, making it possible for teams, products, and working conditions to continue to be improved. Therefore, this literature will present an overview of which agile methods are popularly used for software development, along with explaining the criteria for each method based on the results of research that has been conducted by previous researchers. We offer the findings from the analysis and comprehensive literature review in this part. In addition to addressing the research question posed in section III, the objective is to describe the extracted data. Table 1 displays the findings of data extraction performed on 52 papers acquired over the course of 8 years, from 2018 to 2022.
The purpose of the next section is to provide an answer to the research question posed in part III using the data extraction findings shown in table 1.

No
Year Type of Publisher Method 1 2022 Conference Scaled Agile Framework 2 In this section, we present the results of the analysis and systematic literature review. The aim is to describe the extracted data and to answer the research question described in section III.

RQ1: Trend Studi
Agile study methodology publication trends are seen in Figure 8. Over 52 pieces of literature from the years 2018 to 2022 are cited in the bibliography. As seen in Figure 8, the highest percentage for the use of the agile methodology in trend publications is using scrum, at around 31.4%, followed by extreme programming, at approximately 27.5%. In contrast, the two methods that are most frequently used are the Crystal with a percentage of 2.0%, and DSD with a percentage of 3.9%.

RQ2: Characteristic
This study outlines a number of the traits of each model before tabulating them in accordance with the traits of each process model. Table 2 shows various criteria for each agile method. To make it easier to review the topics to be discussed, we group each character into topic discussions. From the study literature obtained, the criteria will be defined into 13 sub-criteria, which include development approach, recommended iteration time period, team communication, project size, project documentation, design, workflow approach, project coordinator, role assignment, coding, and nature of testing customer interaction: and team collaboration.   Based on the results of trend studies, Scrum is the most widely used method. This is in line with its characteristics, which are quite easy to apply for both users and developers because it is suitable for all types of projects, requires a relatively short duration of time, there are no coding standards to follow, can be done in a cross-functional team, and the resulting design is complex. Furthermore, there is the XP method, which occupies the second position for the trend of using Agile methods. XP has slightly different characteristics from the Scrum method. Based on its characteristics, XP is more suitable for projects with a small scale but has good risk management due to refactoring to simplify coding and accommodate unexpected design changes so that it has certain standards for coding. In its implementation, XP is carried out by self-organizing teams.
Furthermore, the scale method is the least used Agile method. Based on its characteristics, scale is indeed a method that is only suitable for projects with a large scale and requires a long time (8-12 weeks). While other methods are suitable for all types of projects, such as lean, kanban, crystal, and DSDM, it doesn't take that long to work on one project. Each agile method has its own advantages and disadvantages. So that the selection of Agile methods to develop software can be adjusted to the needs and pay attention to the characteristics of the method to be used,.

CONCLUSION
The most pertinent studies for each research topic were selected for this systematic literature review by developing and using inclusion and exclusion criteria. Only eight process models-the Scale Agile Framework, Kanban, Scrum, Lean, Xtreme Programming Crystal, and Dynamic System Development Method-are covered in this study, which focuses on agile approaches. Based on 52 literatures discovered between 2018 and 2022, the results suggest that scrum is the most popular approach, with up to 26.4% of usage, while the Scale Agile Framework is the least popular, with 3.9% of usage. According to a number of criteria, including the development approach, recommended iteration time period, team communication, project size, project documentation, design, work flow approach, project documentation, design, work flow approach, project coordinator, role assigned, coding, testing, and the nature of customer interaction, this study also examines the various characteristics of each process model. However, some attributes cannot be precisely described because of the limits of the many sources used to construct some models.