How To Build Perfect Products (not what you think)
But…
Even if you only have 1 product line, you need to take a portfolio approach to manage your product roadmaps … as a portfolio of customer segments, and a portfolio of competing goals with various ways to realize them. At different time, your focus and allocation to these various aspects of portfolio changes responding to internal and external changes and needs.
This is why you need Responsive PPM (Portfolio Program Management) —to align, allocate and adapt how you make strategic product decisions.