Strictly speaking, a project manager is responsible for keeping a project’s triple constraints (scope, budget, schedule) in control, regardless of what the scope of the project is. That’s already a big job. Should the project manager make the job more difficult by also acting as the “collect requirements” manager, including choosing requirements collection techniques and writing requirements documentation?
I think this statement undermine the authority of a project manager. Taking a simple example of our body, our body has many parts which have a different function. Similarly, in a project, each stakeholder whether internal or external everyone has their own function but project manager is the heart of a project. Apart from managing cost and time project manager must communicate with all bodies of the project.
PROJECT MANAGER MUST COLLECT REQUIREMENT, NOT CREATE THEM.
The collection of requirement come from the business case. Now sometimes project manager is assigned to develop the business case or assigned after business case is developed. Although as a project manager we must bear the burden to manage the triple constraint of the project. We also need to be involved in collecting requirement. Because there is a 4th hidden constraint that is the quality which provides flexibility to another constraint of the project and by collecting the requirement we can identify the quality of the project (it defines the signature management of the project manager).
2.1. Collecting Requirement technic:
The reason we need to choose the technic for collecting the requirement is because of the scope of any project is not clearly define or understood, estimates for cost and schedule is not clearly defined as far as my experience go this is due to improper input from the stakeholder. As a project manager to deliver the project in the triple constraint we need to take an extra effort to identify the requirement.The PMBOK defines a various and proven model to get accurate requirement. I would suggest using this model because it reduces the effort to collect the accurate requirement.
Documentation is necessary as it allows you to generate progress report and set cost and time estimate and in future if as a project manager we encounter similar project this document can be a way to reduce the effort to collect requirement.
Let me know your views,
I am your friendly PM!