Contents
Introduction
“We’re Agile — we don’t need specs.”
That mindset sounds bold — until it costs you a six-figure rewrite.
Agile methodologies, such as Scrum, are designed for speed, adaptability, and continuous delivery. However, that doesn’t mean you should skip the planning stage, especially when building complex, regulated, or mission-critical systems. Clear requirements often mean the difference between a successful agile project and a chaotic one.
This article will explore how requirements specification and agile development fit together, why that matters, and how a hybrid approach can offer the best of both worlds.
Requirements
What is a requirement?
A requirement is a statement that defines a system’s function or behavior. It can describe:
- Business rules (e.g., “Only verified users can access premium content.”)
- Functional needs (e.g., “The user must be able to reset their password.”)
- Quality needs and constraints (e.g., “The system must respond within two seconds.” or “The system must provide a data exchange API with our current CRM system.”)
Requirements are not just technical instructions; they’re strategic. They translate business goals into actionable development work and define the direction and constraints of development.
What is a requirements specification?
A requirements specification is a structured document or artifact that captures and organizes all known requirements. It serves as:
- A contract between stakeholders and the development team.
- A blueprint for product owners, designers, developers, and testers.
- A reference for validating the final product.
There are two perspectives:
- Customer requirements (CR): High-level goals, expectations and mission-critical constraints formulated by the customer, often derived from a project’s business case (e.g., “The system must comply with GDPR.”).
- Requirements specification (RS): Detailed and extended items derived by the development team from analyzed customer requirements to provide a coherent requirements base for the project (e.g., “Encrypt user data at rest using AES-256.”).
Customers generally define the “what“, while the development team defines the “how“.
What are epics, stories, and tasks?
In agile, especially in Scrum, requirements are stored as epics, which are more high-level, and stories, which are more detailed. Finally, tasks are actionable items ready for implementation:
- An epic is a large, strategic feature or initiative (e.g., “User management.”).
- A user story is a small, user-focused requirement (e.g., “As a user, I want to change my email address.”).
- Stories are broken into tasks, which are the technical steps needed to implement them.
These items live in the product backlog, which is continuously refined and prioritized. Unlike traditional specifications, stories are lightweight and evolve over time.
Requirements in traditional development
Traditional software development (e.g., waterfall, V-model) builds on a strong foundation of requirements, which ideally describe the development project in detail from the outset:
- All requirements are defined upfront.
- Typically, each phase (design, development, and testing) must be completed before the next one begins.
- Changes are discouraged and often costly.
- This approach works well for stable, predictable projects and industries that demand strict requirements management due to safety-critical product development, such as automotive and aerospace.
Requirements in agile development
In contrast, agile development is based on the paradigm of continuously evolving insights from previous product increments and needs, so epics and stories can change at any time:
- High-level epics coexist with more detailed user stories while refinement occurs for items that will be implemented in an upcoming sprint.
- The emphasis is on working software (product increment) rather than documentation.
- It encourages frequent feedback and course correction.
- This approach is ideal for fast-changing or exploratory projects, such as startups or digital products.
Hybrid Approach
The problem with “just start building”
Agile methodology encourages teams to start small, iterate quickly, and adapt as they go. That’s great – until it isn’t.
In practice, many agile projects suffer from the following issues:
- Unclear scope: Teams begin development without a shared, mutually confirmed understanding of what success looks like. The absence of an expressly defined product vision and strategy can lead to ambiguity and confusion.
- Misaligned expectations: Stakeholders assume certain features are “obvious,” even though they were never discussed or documented.
- Technical rework: Early architectural decisions that do not support later requirements lead to costly refactoring.
- Interoperability and compatibility issues: A lack of clear system requirements may result in a system that functions properly but never achieves the desired outcome due to incompatibilities or unsupported third-party systems critical to the intended outcome.
- Compliance gaps: Legal and regulatory requirements (e.g., security and privacy) are often discovered too late, sometimes even after deployment.
Without an initial requirements specification, agile teams risk building the wrong thing quickly, which is arguably worse than building the right thing slowly.
For MVPs, this approach is fine and recommended. However, this is especially dangerous in projects where:
- Certain features are non-negotiable.
- There are external dependencies, such as APIs, plugins, or legacy systems.
- The product must meet compliance or certification standards.
Agile doesn’t eliminate the need for planning. It simply changes when and how planning occurs. The advantages of agility typically outweigh the disadvantages of uncertainty. However, for certain requirements, waiting is not an option.
Agile development with requirements specification
An effective solution to this dilemma is a hybrid approach that maintains the integrity of agile development while establishing a solid foundation of mandatory requirements, including high-level business needs and detailed constraints regarding compatibility, interoperability, and compliance. This requirements baseline, determined at the beginning of the project before development begins, is then used to derive epics, which are processed as typical agile items throughout the project. Of course, mandatory requirements must not change without expressed, agreed-upon change requests that follow a thorough impact analysis.
This hybrid approach could be applied in 5 steps as follows:
- Start with a “requirements phase” to:
- Review and analyze the customer requirements document, if available.
- Determine the mission-critical, high-level requirements. A proper product vision and strategy can help with this.
- Determine the mandatory, detailed requirements and constraints (e.g., those regarding compatibility, interoperability, and compliance).
- Lock these into a requirements specification baseline.
- Derive epics and stories from the complete requirements specification. Ensure that these items are traceable to the original requirements.
- Use these items as a starting point for an initial backlog to continue agile development.
- Control changes to the initial requirements specification regarding mandatory requirements during the course of the project. Traceability helps distinguish between mandatory and non-mandatory requirements derived later on.
This approach is particularly useful in the following situations:
- Applications that require regulatory compliance (e.g., HIPAA compliance).
- Software that relies on interoperability with other systems (e.g., specific APIs).
- Solutions with specific system requirements (e.g., operating systems, hardware drivers, and embedded target platforms).
- Any solution where the initial, high-level requirements are well-defined and unlikely to change. This is particularly relevant when a clear product vision and strategy are in place.
Example:
A logistics platform must integrate with a government customs API. That’s non-negotiable. But how the dashboard looks? That can evolve sprint by sprint.
This hybrid model allows teams to move fast without breaking the rules.
Benefits and limitations of the hybrid approach
✅ Benefits:
- Risk Mitigation: Critical requirements are locked in early.
- Fast delivery: Agile sprints maintain high momentum.
- Stakeholder confidence: Everyone knows which requirements are fixed and which are flexible.
- Better planning: Teams can estimate and prioritize more clearly when they have a clear direction.
- Improved traceability: It’s easier to map features to business goals and compliance needs.
❌ Limitations:
- Upfront effort: Requires time and alignment before development begins.
- Complexity: Teams must manage both fixed and evolving requirements.
- Risk of rigidity: Over-specifying can stifle innovation if not balanced carefully.
Summary
Agile doesn’t mean skipping the planning stage. Planning doesn’t mean locking everything down, either. A hybrid approach, anchored in clear, fixed requirements but executed with agile flexibility, can help teams deliver faster, safer, and smarter.
The key is knowing which aspects must stay fixed and which can evolve.
By combining the discipline of traditional requirements engineering with the adaptability of Agile, your team can build software that is fast, flexible, reliable, compliant, and aligned with business goals.
At entrepreneurboat, we build projects based on this hybrid approach to align with clients’ needs, mitigate risks, and maintain agile, fast development.
Have a project idea in mind?
Let’s find out how we can help you turn your vision into reality!