After your requirements are defined—including goals and objectives, diagrams and models of pertinent information, business processes, and the business events that organize data and processes—it is time to communicate your requirements to your selected vendors.
Requirements are communicated on an ongoing basis. That's right, you don't just tell them once and walk away; you have to stay with the process:
First you transmit your requirements documents. It is often useful to set up a face-to-face meeting to review the requirements and make sure you are communicating effectively.
Next, you'll need to confirm that your audience, the vendor, understands what you need, and feels able to deliver it. It's important ...