OOP – How to refactor a “pyramid architecture”

Unbeknownst to me while I was building it, I built a “pyramid” architecture. I did not realize this until I laid it out in my new Visual Studio 2013 Layer Diagrammer. Each layer depends on the layer below, and all the other layers below that.

Check permissions on top layer before going deeper

I’m building a four layer simple architecture with the following layers:

How to structure an ERP system in a modular way, with module hierarchy and where do application layers stand in this?

I built an asset management system (a web application) using C# ASP.NET in MVC structure. My project is built upon the ASP.NET Boilerplate template, which includes 5 layers by default. These layers are:

Understanding dependency inversion

According to the definition by Robert Martin, high level modules should not depend on low level modules, instead both should depend on abstractions.