Documenting Requirements - Is it old-fashioned?

With the advent of Agile approach, one school of thought strongly believes that documenting the requirements (specially detailed version) is not needed any more. As per that school of thought, only A high-level requirements description is needed. As collaboration amongst the team members can compliment it.

Other school of thought believes that we still need to have a detailed requirements document, just the team collaboration is not enough.

We need to consider a few factors before taking a decision on the documentation approach. This will also help you in making the right decision about documenting requirements.

Complexity and Size of the project

A large project has many dimensions to consider. Many teams will be involved (even though using Agile approach), managing dependent functionalities. Without detailed documentation having details of interfaces and agreement between the requirements, it would be next to impossible to ensure everything is taken care of by the design and dev teams.

A complex project has its own set of challenges. The complexity can be related to certain domains like AML and that requires precise description of the work to be done.

Nature of the project

A project in the highly regulated field, like medicine, healthcare, taxation, government policy, financials, GDPR applicable fields, must have detailed and specific documentations to avoid legal or any regulatory issues.

Data-intensive projects

All the data-driven projects whether an analysis and reporting project or an AI project requires to capture detailed business rules, simple to complex data mapping needs and so on. We cannot avoid detailed documentation in this case as well.

These are some of the factors which makes the case for having a detailed requirements documentation. It has nothing to do with being Agile or non-agile, its more about the need and the context.