Im studying about software architecture but Im with some doubts. Because for example if you dont have any or much experience in developing a application how can you build an useful architecture for a application?
For example if we already have the requirements phase for a web application like a ecommerce app where we have use cases like: buy product, create new product, login, etc, with a structure like the use case below for create a new product.
How we can go from these requirements use cases to build/describe an useful architecture before building the system if you only know that you will use a framework like codeigniter but you only know how to do basic things, but never created a complete app? That is, how to build/describe an useful software architecture for a system if you never build a complete app and therefore you dont know very well how you will build the app, so how can we build/describe that architecture before implementing it?
Example of use case: