Eiffel's Single Product Software Development Model

It is important to understand that developing software with 
Eiffel is fundamentally different from developing using any 
other method and toolset. This is because Eiffel supports a 
single product development model. 

This means that throughout all stages of development, there 
is only one product ... and there is one notation in which 
this product is expressed. This means you never have to switch 
notations or modeling mechanisms during the course of a 
project. And, of course, it also means that all your efforts 
go directly into what will eventually become your final 
product -- a running software system or a library of software 
components.

Of course, as you work toward a finished software system or 
library, your role changes according to your current activity. 
If Eiffel only provided a one-dimensional view of your software 
product like most other methods and languages do, then this 
single product model really would not be workable. But the 
elegant design of Eiffel comes to the rescue. It allows you to 
express and record the products of all phases of development 
in a single product, plus it empowers EiffelStudio to provide 
you with many different views of your single product. You 
choose to see your software using a view that is appropriate 
to the lifecycle phase and your current role.