1、It's defined by which horizontal or vertical slice of the world you connect yourself with.
2、The vertical slice can then be refactored until the final system requirements are met.
3、The vertical slice does not necessarily cover every possible contingency; for example, a vertical slice may not provide error checking or may "stub out" various pieces of the technology.
4、However, a migration effort is not concerned with building a vertical slice; it is concerned with migrating an existing one.
5、At the very least, an "unsuccessful" vertical slice migration will identify the hard problems and allow you to adjust your development schedule accordingly.
6、If it is possible, migrate your configuration as vertical slices, measure the time required to migrate a single slice and use that information to estimate the entire effort.
