“[A] good problem description had to satisfy everyone. If two people saw a problem from a different point of view, both people’s points of view were merged into the problem description, making the problem more complicated, and making solutions sometimes harder to achieve. But this was essential to addressing porting problems, for example. One couldn’t just solve how a file system operation would work on one operating system unless the solution was going to work on other operating systems, too. On the other hand, the “proposal” field was very different. If two people disagreed on a proposal, they each wrote their own proposal so that proposals could be internally consistent and coherent. This meant that a single problem often had several proposed solutions with different costs and benefits, and the committee had to decide which was the stronger proposal.”
From http://www.nhplace.com/kent/Papers/cl-untold-story.html