Difference Between SDLC vs Agile: This article is not intended to be a complete, all-inclusive treatise on SDLC vs Agile methodologies. The purpose of this review is to highlight the major differences between each methodology and their relative advantages and disadvantages in order for developers to make an informed decision as to which approach best fits with their software development model; or, if they want to use some variation of the two methods.
What is SDLC?
SDLC is an acronym for Software Development Life Cycle. It is a set of steps, listed below, used to produce software that provides the highest quality possible within the time and budget constraints established by the business.
The SDLC follow-on Agile development has been suggested as one of the reasons why both are often confused with each other and why neither is clearly “better” than the other. The problem with this argument is that many of the steps in SDLC are performed even if Agile development is used; it might be more appropriate to say that both SDLC and Agile exist because they fill different needs.
There are a few popular models of SDLC are there, like:
- Waterfall Model
- Iterative Model
- Spiral Model
- V-Model
- Rational Unified Process (RUP)
What Is Agile?
Agile software development was created as a response to poorly performing software processes (SDLC) that were rigid, controlling, and costly.
Agile development is characterized by:
Individuals and interactions over processes and tools Working software over comprehensive documentation Customer collaboration over contract negotiation Responding to change quickly over following a plan That is not to say that Agile methodologies are devoid of any structure. There are several Agile frameworks that methodologies follow, the most popular being Scrum and eXtreme Programming (XP).
Benefits of Agile:
- Focus on customer satisfaction.
- Working software is delivered to the customer as soon as it is ready.
- Iteration (short development cycles) allows errors and deficiencies to be detected and corrected earlier in the development cycle.
- A sense of accomplishment motivates employees, who feel valued because they see their work having a direct impact on their customers.
- A lower cost-per-defect ratio reduces overall project costs due to the rapid delivery of higher quality products.
- The ability to respond to changing customer requirements is a competitive advantage, as customers no longer have to wait for an extended period (months or years) to receive the product they want.
Difference Between SDLC vs Agile
Here are some of the key differences between SDLC vs Agile.
1. Complexity
SDLC is a process-based approach to software development whereas Agile is about people and the interactions between them. This difference in perspective has profound effects on how each methodology manages complexity. In SDLC, solutions are built on top of existing code, which means that there’s a gradual increase in complexity as time goes on. On the other hand, Agile resolves complexity by throwing away code.
2. Commitment/Commitment vs Planning
In SDLC, contracts are signed and changes are prevented without management’s approval. There is room for negotiation on both the financial and functional sides of a project because of this commitment to an original plan. In Agile, the teams commit to delivering functionality on a regular basis and that is it. This freedom allows for changes in direction based entirely on customer needs.
3. Schedule/Time and Cost Estimates
Software development time estimates are very common in SDLC. They’re usually calculated using normal distribution techniques. Agile projects do not typically include time estimates, since they tend to underestimate the amount of work that is actually needed. Instead, Agile teams use a concept called “velocity” to calculate how much work can be done in a given period of time. Velocity is measured over an iteration and includes only the committed functionality or story points. An iteration might last between 2-4 weeks, depending on the team and product.
4. Programmer/Project Manager Ratio
Agile teams tend to organize in self-constituted groups called “distributed Agile teams.” These teams are usually made up of 3-5 people, including both programmers and project managers who have a special focus on the customer. In many SDLC environments, these roles are separated into individual jobs.
5. Product Owner/User Participation
In Agile environments, the product owner is a liaison between the customer and the Distributed Agile team. The product owner ensures that all customers’ needs are addressed, but also advocates for what’s best for business. In SDLC environments, user participation usually goes through a PM who represents the customer. The product owner combines business and technical knowledge to create valuable products that meet the needs of both parties.
6. Testing/Debugging Techniques and Metrics
In SDLC environments, testing is usually done after coding is complete, which means that bugs are found at the end of a project when it’s too late to fix them. Agile approaches testing and debugging in a different way. Unit Testing is done early and often throughout the project, ensuring that defects are caught before they become serious problems. Teams also use “Test-Driven Development” (TDD) where programmers write tests first, then code for those tests after. In addition, Agile teams use a concept from Lean PDCA called “Definition of Done” to define when the project is actually finished. In Agile, this includes not only code that works, but also includes documentation and automated tests.
7. Features/Functions and Acceptance Criteria
In SDLC approaches to software development, requirements are often described as a list of features or functions. This approach is good for making sure that the code fulfills specific needs, but doesn’t do much to address changes in direction due to customer needs. Agile approaches requirements more liberally and focuses on what customers want instead of how they get it. Acceptance criteria are used to specify when work can be considered done. Teams will use these criteria to define the “Definition of Done.”
8. Integration and Performance Testing
In SDLC environments, integration is typically done at the end of a project and testing is primarily focused on functionality. Agile teams integrate frequently to check for bugs early on in development and isolate issues as soon as they’re found instead of trying to find them all at the end. Performance testing is done more in Agile environments, where developers use metrics on previous iterations of a project to estimate how long it will take to complete new tasks.
9. Planning/Change Control and Requirements Traceability
Planning in SDLC environments can be very time-consuming and difficult since they can’t be changed as easily. Agile projects have a shorter planning cycle and change control is built into every iteration, which means that changes can happen easily with minimal impact. Agile teams use automated “Continuous Integration” (CI) tools to make sure that everyone has the current version of a project at any given time. This technique helps with requirements traceability because project history is visible to all concerned parties.
10. Standups and Retrospectives
In Agile environments, “Standup” meetings happen every workday at the same time for all teams in a group, often including programmers, PMs, testers, and customers. Standup meetings keep everyone up-to-date on what is happening in the project and allow for quick responses to issues. In SDLC environments, meetings tend to be more specific about what they’re about and are often subject-specific. Lastly, Agile Retrospectives happen at the end of each iteration. During a retrospective, team members talk about where they went right or wrong, then apply those lessons to the next iteration. This allows projects to go in the right direction without losing too much time if a development path needs to be changed.
SDLC vs Agile In Short Form
| Agile | SDLC |
|---|---|
| Agile uses self-organization | SDLC takes a top-down approach |
| Agile is focused on producing working software | SDLC is focused on producing a complete system. |
| Agile emphasizes change | SDLC emphasizes following a plan. |
| Agile is a philosophy | SDLC is based on proven methodologies. |
| Agile methods deliver working software in short development cycles | SDLC is a process that takes place over months and years. |
| Agile promotes collaboration between customers and developers | SDLC is more focused on the development team. |
| Agile methods are considered a lightweight process since it focuses on producing value sooner than later. | SDLC is a heavyweight process since it focuses on detailed documentation and control. |
| Agile methods are less costly because you can deliver working software to customers sooner than later. | SDLC is costly because it requires detailed analysis and documentation and control over the software development lifecycle. |
| Agile methods are less bureaucratic, because developers have more freedom to self-organize, and it does not require vast and elaborate documentation. | SDLC is bureaucratic because of the exhaustive planning requirements, control over the process, and detailed documentation. |
| Agile promotes higher employee morale since they feel valued and have a sense of accomplishment. | SDLC is considered less motivating because employees have little creativity and say in the process. |
| Agile is a more expedient approach to quality assurance since working software is delivered to customers within a short period of time. | In SDLC, quality assurance may take months or years. |
| Agile considers the economic landscape since it wants to deliver value quickly. | SDLC focuses more on technical issues than on customer satisfaction. |
In Short Form Comparison Between SDLC vs Agile
- Agile has a better chance of completing projects on time than SDLC, since it has shorter development cycles.
- Agile has a lower cost of defect ratio than SDLC.
- Agile is more customer-focused than SDLC.
- Agile is more iterative than SDLC since it uses short development cycles to deliver working software.
- Agile considers changing customer requirements since it is more flexible than SDLC.
- Agile has a greater chance of being completed on time than SDLC.
- Agile is better at managing customer expectations than SDLC.
- Agile has a greater chance of being completed within budget than SDLC.
