Answer.

History of the question:

Complex requirements are often formulated at a high level of abstraction or contain multiple hidden conditions and exceptions. If such requirements are not decomposed and clarified, misunderstandings may arise between the client, developers, and testers.

Problem:

Ambiguous or insufficiently decomposed requirements lead to the team 'filling in' the details on their own. As a result, business value may remain unrealized or distorted, and fixing this becomes much more difficult and expensive.

Solution:

The system analyst conducts a detailed analysis of the requirements using decomposition techniques (Use Case Diagram, Activity Diagram, User Stories according to INVEST, Event Storming, decomposition tree). It is important to form scenarios (basic/alternative/exceptional flows), build decision tables and transition matrices, and finally verify each "node" through edge case examples together with the client. After decomposition, the analyst collects all parts, analyzing integration points and ensuring consistency.

Key features:

Detailing requirements to unambiguous specifications
Including alternative and exceptional scenarios
Creating artifacts that are transparent for testing and further support

Trick questions.

Is a textual description of a User Story scenario sufficient?

No, a user story alone is not enough: sequence diagrams, edge case examples, UI mockups, and decision tables for complex business logic are needed.

Does decomposition automatically ensure the absence of contradictions between requirements?

No, decomposition must be accompanied by the consolidation of conflicting requirements, regular review sessions, and dependency analysis.

Can decomposition be solely entrusted to developers or testers?

No, the analyst is responsible for completeness of detailing. If this is handed over to other roles, a multitude of interpretations and discrepancies may arise.

Typical mistakes and anti-patterns

Leaving complex requirements "as they are" without deep analysis and decomposition.
Skipping exceptional scenarios: describing only the "happy path".
Conducting decomposition alone without involving the client or team.

Real-life example

Negative case:

The business client wrote, "The system must calculate a discount for each client individually." The implementation went with a rigid discount scheme. During testing, it became clear that there were more than a dozen hidden parameters that were not identified at the formalization stage.

Pros:

Quick start

Cons:

Mismatch with business realities
Massive rework

Positive case:

The analyst conducted an Event Storming workshop, identified all parameters and conditions for the calculation. Built a decision table and sequence diagrams, coordinated edge case examples with the business. The requirement became clear and verifiable, and errors were discovered before the start of development.