I think application types, verticals, and scenarios are a helpful backdrop for product-line engineering. You can use it to organize policies and requirements. It’s a way to increase precision. For example, it’s one thing to build a Web application. It’s another to build a Web application for a financial institution. How you implement security, performance, and other quality attributes has a lot to do with the application type and the scenario or context you are in.
App Types, Veriticals and Scenarios Conceptual Framework
Here’s a simple model I use when I think about product line engineering.