“The concept behind the inverted pyramid format is relatively simple. The writer prioritizes the factual information to be conveyed in the news story by importance. The most essential pieces of information are offered in the first line, which is called the lead… The writer then provides the rest of the information and supporting contextual details in descending order of importance, leaving the least essential material for the very end.”
Robert A. Rabe.
The inverted pyramid writing style is used heavily in newspaper journalism as it allows the editor to cut from the bottom when they need to reduce a story to optimise a page layout. They intuitively know that the last paragraphs are the least important.
When planning an OSS, the inverted pyramid model helps to prioritise the elements of your implementation from highest to lowest. Then if you need to reduce scope for whatever reason during the course of an implementation, you know exactly what to de-scope… Start at the bottom of the pyramid because you’ve pre-determined that it’s the least important.