1. Software Development Life Cycle (SDLC)

In today’s world, software has become an indispensable necessity for businesses of all sizes across various industries. Whether small or large, every company, regardless of its field, interacts with software processes. Software development is not just about coding; it is a highly complex process. Therefore, like any other project in a company, every phase of the software development process must be carefully and meticulously defined. The Software Development Life Cycle (SDLC) emerges as a standard for this definition process.

The Software Development Life Cycle, abbreviated as SDLC, is an approach that aims to plan all stages a software will go through during its production and use, step by step. As shown in Figure 1, SDLC typically consists of six main steps:

Requirement Analysis: This is the first and most critical stage of

the SDLC. In this phase, essential elements such as customer requirements, project objectives, budget, required resources, technical specifications, methods to be used, and delivery dates are determined.

Planning: Building on the requirements analysis, the project team

roles, programming languages, tools, and hardware requirements are determined in this phase.

Design: Based on the information gathered from previous stages, the

basic structure of the software is created. During this phase, the software’s interface is designed, and functionalities are defined.

Development: This is the phase where the features and functionalities

defined in the design process are implemented through coding. Developers make the design elements operational, resulting in a prototype of the software.

Testing: In this phase, it is evaluated whether the criteria

determined in the requirement analysis are functioning correctly and reliably. The software undergoes various tests such as performance tests, stress tests, usability, and security tests. Errors found are fixed, and improvements are made. After completing all testing processes, the software is ready for deployment.

Deployment: The software is made available to the end user. Feedback

from users plays a critical role in improving the software.

Additionally, it is crucial for solving any errors that may arise during the software’s operational life.

2. Roles in the SDLC Process

The Software Development Life Cycle (SDLC) covers all phases from the initial idea to the maintenance phase. Throughout this process, professionals with different expertise contribute critically to the correct development and successful delivery of the software. Below are the key roles in SDLC, their responsibilities, and the skills required for each role.

Business Analyst: The business analyst collects, analyzes, and

communicates customer and user requirements to the project team. Their primary responsibility is ensuring that the correct requirements are defined for the software development process.

Key skills for a Business Analyst:

• Proficiency in requirements gathering and analysis tools (e.g., Jira,Confluence, UML)
• Process modeling and documentation skills (BPMN, workflows)
• Basic data analysis, reporting, and visualization capabilities
• Strong analytical thinking, problem-solving, and effective communication skills

Product Owner: The product owner defines the vision for the software,

develops it, and drives the product development process. They prioritize and focus on developing the most valuable features, considering user needs, market requirements, and technical limitations.

Key skills for a Product Owner:

• Strategic thinking and decision-making ability
• Ability to analyze the market and understand customer feedback
• Creating and maintaining the product roadmap
• Leadership, team management, conflict resolution, and negotiation skills

Project Manager: The project manager oversees the operational aspects

of the project: schedules, budget, resources, risks, and quality. Their primary goal is to ensure the project is completed on time, within budget, and with the required quality.

Key skills for a Project Manager:

• Organizational, time management, and planning skills
• Risk management and problem-solving under crisis situations
• Resource planning, effective communication, and reporting skills
• Decision-making, working under pressure, and fast problem-solving skills

Software Developer: The software developer designs, codes, tests, and

maintains the software according to technical requirements. Their most important responsibility is to ensure the software is efficient, secure, and user-friendly.

Key skills for a Software Developer:

• Proficiency in programming languages and development tools (Python, Java, C++)
• Knowledge of software architecture and design patterns
• Testing, debugging, and code optimization skills
• Ability to be a good team player and learn quickly

Test Engineer (QA Engineer): The test engineer checks whether the software meets quality standards and plans and executes testing processes. They are responsible for ensuring the software functions correctly and reporting any errors.

Key skills for a QA Engineer:

• Knowledge of manual and automated testing processes
• Writing test scenarios, bug reporting, and using testing tools (Selenium, JUnit, etc.)
• Attention to detail, analysis, and problem-solving skills
• Patience and a meticulous working habit

Solution Architect: The solution architect designs the technical infrastructure of the software and leads the project. They ensure that the software components work together and that security and performance requirements are met.

Key skills for a Solution Architect:

• Knowledge of system design, infrastructure, and integration
• Ability to perform performance and security analysis
• Knowledge of cloud solutions, distributed systems, and strategic thinking
• Analytical thinking, leadership, and excellent communication skills

DevOps Engineer: The DevOps engineer integrates software development and operational processes. They ensure that processes are automated, integrated, and efficiently managed during the deployment.

Key skills for a DevOps Engineer:

• Infrastructure management, system automation, and scripting knowledge
• Knowledge of CI/CD tools and cloud platforms (AWS, Azure, GCP)
• Knowledge of containerization, virtualization technologies, and security
• Team communication, collaboration, and crisis management skills

Release Manager: The release manager ensures the safe and smooth transfer of software updates to the production environment. They manage all stages of deployment and ensure that new releases reach users on time and without errors.

Key skills for a Release Manager:

• Integration of software releases and management of CI/CD processes
• Change management and version control processes
• Effective coordination with all stakeholders and risk management
• Process improvement and crisis management skills

Each role in the SDLC process plays a vital part in ensuring that software projects are completed successfully. The unique skills of each position contribute to the effective functioning of project teams and help deliver high-quality, secure, and user-centered software.

3. Example Scenario

Request: A Telecom Operator Developing a New Campaign Management System

A telecom operator wants to develop a Campaign Management System that offers personalized internet, talk, and SMS plans to its customers.

This system will automatically suggest campaigns based on customer segmentation and usage habits, and these suggestions will be displayed through a mobile application.

3.1.Analysis

• Business Analyst: Writes the user scenarios and business requirements.
• System Architect: Defines the technical requirements.
• Security Specialist: Ensures that customer data complies with data protection regulations (e.g., GDPR).
• Release Manager: Reviews the release scope.

The campaign will be automatically assigned based on customer usage data. It will be decided when and how the campaigns will be suggested to the customer. The release scope will be reviewed, and a decision is made to release the beta version to internal test users.

3.2.Planning

• Project Manager: Determines the project timeline, budget, and resources.
• Business Analyst: Gathers the business requirements for the campaign system.
• Product Owner: Defines the priority campaign types and customerexpectations.
• Release Manager: Creates the release schedule. The MVP (Minimum Viable Product) is defined.

The date for the initial version release is determined. The marketing team requests personalized campaigns, and the Release Management decides that only internet-related campaigns will be included in the first phase.

3.3. Design

• UX/UI Designer: Designs the user interface.
• Database Administrator: Determines how campaign data will be stored.
• System Architect: Designs the system architecture.
• Release Manager: Defines the strategy for the environments to be used.

The design for displaying campaigns on the “My Campaigns” page is created. MongoDB is chosen as the database. A pre-release version of the campaign will be available for a limited group of users.

3.4.Development

• Backend Developer: Codes the campaign engine.
• Frontend Developer: Develops the user interface.
• Mobile Developer: Integrates the mobile application.
• Release Manager: Tracks code management and decides which branch will be released in which version.

3.5.Testing

• QA Engineer: Performs functional tests.
• Automation Test Specialist: Writes tests using Selenium.
• Security Specialist: Tests data security.
• Release Manager: Reviews test results and adjusts the release date based on the error rate.

During the beta tests, if errors are found in campaign recommendations, the version 1.0 release may be delayed.

3.6.Deployment

• Release Manager: Manages when, how, and where the release will be deployed.
• DevOps Engineer: Manages CI/CD processes.
• System Administrator: Configures the servers.

The deployment is initiated with a 10% user base and can be expanded later. If a major issue is detected, the system can roll back to the previous version. The application is published on app stores.

3.7.Maintenance

• Data Analyst: Analyzes the campaign’s performance.
• Release Manager: Plans urgent fix releases.

A bug-fix version 1.0.1 is released, and based on customer feedback, version 1.1 can be developed.

4. Agile Methodology

Agile is a software development methodology that breaks projects into small, manageable parts, aiming to gather regular feedback at each stage of the process. Instead of delivering a single final product, Agile focuses on delivering incremental updates of the product throughout the project lifecycle, responding quickly to customer requirements, and continuously improving quality.

Agile methodology can be implemented with various frameworks, with Scrum and Kanban being among the most widely used.

4.1.Scrum

Scrum is a framework based on Agile principles, used for managing complex projects and product development. It uses short planning cycles, known as sprints, with the goal of delivering a working product at the end of each sprint. Teams work in small, self-organized, cross-functional structures, and at the end of each sprint, feedback from customers or stakeholders is gathered to continuously improve the product. The main objective of Scrum is to quickly adapt to changing market demands and project requirements.

Core features of Scrum:

• Short Sprints: Typically 1-4 week periods where targeted tasks are completed, and the product is reviewed at the end of each sprint.
• Customer Feedback: At the end of each sprint, the product status is reviewed and feedback from customers or stakeholders is incorporated into the next sprint.
• Team Collaboration: Team members work together to reach the set goals.
• Visualization: Workflow is tracked, and the status of tasks is monitored using tools like Scrum boards or digital tools.

Roles in Scrum:

• Product Owner: Responsible for the business goals of the project, defines requirements and priorities, and sets the vision for the project.
• Scrum Master: Ensures Scrum processes are followed correctly and helps the team work efficiently.
• Development Team: The team responsible for designing, developing, and testing the product.

4.2.Kanban

Kanban is an Agile methodology that focuses on visualizing tasks and improving workflow. The main principle behind Kanban is to display tasks on a board to track progress throughout the process. The board typically includes columns like “To Do,” “In Progress,” and “Done.” To balance the workload, specific Work In Progress (WIP) limits are defined, ensuring that the team does not overload any part of the process, preventing bottlenecks.

Core features of Kanban:

• Visualization: Tasks are displayed on a Kanban board, which is divided into columns like “To Do,” “In Progress,” and “Done.”
• Work In Progress (WIP) Limits: To balance workflow, tasks in each column are limited. This ensures that tasks are not started before previous ones are completed, preventing bottlenecks.
• Continuous Improvement (Kaizen): The process focuses on identifying and resolving bottlenecks to improve efficiency.
• Flexibility: Kanban doesn’t require fixed cycles or sprints; tasks are added as they become available, making it easy to adapt to changing priorities.

Roles in Kanban:

• Team Members: Individuals who perform tasks listed on the Kanban board.
• Kanban Leader: Person who supports the implementation of efficient processes.
• Product Owner: Responsible for prioritizing tasks on the Kanban board.
• Coordinator (Optional): In larger teams, a coordinator ensures proper team collaboration.

5. Comparison of Waterfall and Agile Methodologies

Waterfall and Agile represent two distinct approaches to software development. Waterfall is a traditional, linear approach, while Agile is a flexible and iterative methodology. Both methodologies aim to structure the software development process, but they have significant differences and advantages.

Waterfall offers a structured approach suitable for long-term projects with clearly defined requirements, while Agile is ideal for projects that require flexibility and rapid iteration. The success of a project largely depends on selecting the appropriate development method.

Waterfall and Agile Hybrid Models

In recent years, many companies have started using hybrid models that combine Waterfall and Agile approaches. A model like Agile-Waterfall provides flexibility and structured progress, particularly for large projects. In this hybrid approach, Waterfall is used for structuring the main phases of the project, while Agile’s iterative cycles are applied during the development phase. This allows for both control and flexibility to handle changes effectively.

Software Development Tools and Technologies

Both methodologies use various tools to improve the efficiency of the process. For Agile projects, tools like JIRA, Trello, and Asana are commonly used for task tracking and feedback management. For Waterfall projects, tools like Microsoft Project are preferred for comprehensive planning and scheduling. These tools help ensure that projects are completed on time and teams manage their tasks effectively.