The inside-out engine is the product or program lifecycle. Even with only a handful of offering each will have its own lifecycle with hold ‘em or fold ‘em decision for each.
The outside-in engine is the MCPESTEL engine. MC who? Market, Competition, Political, Economic, Social, Technology, Environmental, and Legislative/Legal are segments that different members of your enterprise watch, and that’s a good thing. On average every 8 days something of significance to your project changes among these segments. Stakeholders keeping you informed about changes in their purviews also keep changes in course small and manageable.