Business people and developers must work together daily throughout the project.

The responsibilities of the business owner are to do just-in-time planning, filling in the details in the backlog sufficiently that the team will be able to understand the work that needs to be done in the next sprint. They define what it means for a story to be completed. In addition, they are to serve the informational needs of the team, interfacing with the end users and the subject matter experts.

During the course of development, questions are bound to arise. Given a choice of going one way or another, if it is a technical question, then it is up to the team. But if it is a domain or a business choice, then the Business/Product Owner needs to make that decision. For that reason, the the business owner should expect to be working with the team on a daily basis. They should make themselves available to them, perhaps even co-locating with them. They should be proactive, cultivate a culture of questions and feedback from the team.

An all too common mistake is to have a business owner that shares his time between projects. The problem there is, all of the teams suffer as a result. While the company may be paying one less salary, they are getting less productivity out of 15 or more people. Not a wise trade-off.