(‘Definitive’? c’mon, really?)
Definitive is indeed a strong word, not to be taken lightly. It is used here because the pipeline risk assessment methodology described herein is more efficient (cheaper to set up and use), more intuitive, and more accurate than any competing approach. Since it emerges from first principles of science, it is also unlikely to be superseded—it should change only if our understanding of the underlying science changes.
The text, Pipeline Risk Assessment: The Definitive Approach and Its Role in Risk Management, adds more explanation surrounding the idea that this approach is indeed definitive.