OWIN: Open Web Interface for .Net. Before starting, keep in mind that owin is just a specification and not technology or framework. Owin in simple words is an standard interface between .Net web server and web application. Basically OWIN is designed with a goal to make web servers and application decoupled. It also heads towards encouraging developement of simple modules for .net web development.

Untill now decoupling was focused by developers through taking steps like creating multilayers in the application that interacts with use of interfaces, using SOLID principles , design patterns etc. Now owin doesn't aim to decouple in code. Its decoupling of application and web servers , where application is hosted.

Its advantages include :

1. Any middleware component can be added or replaced into the application without affecting other components.
2. Use of self hosting , removes the dependency on web servers to host .

KATANA :

Now question arises, what is Katana. As I already mentioned that OWIN is a specification and not technology , so Katana is a open source project by Microsoft that is built on Owin specifications. For example , Asp.net Web API which is based on self hosting concept of Owin. We will discusses this in more details later.

Any application having Owin specification is capable to talk with web server having owin compatible hosting layer. Katana has implemented Owin and could host ASP.NET Web API, ASP.NET SignalR and many third-party frameworks on several servers, including IIS (and IIS Express), Katana's self-host server and custom hosts.

I will come up with my new blog with more details about hosting provided by Owin.