If you are writing middleware components to share with others please read the middleware development guide.
If you are writing an OWIN application and want to consume components and configure your OWIN pipeline please read the application development guide.
Note that there is a comprehensive Wiki for this project.
OWIN represents a great leap forward in standardizing the interface bewteen the hosting environment and the web application. It allows any web application to run on any hosting platform, and this standardization is helpful to everyone involved in web development.
Another great thing about OWIN is that it defines only one very straightforward interface that does not place any constraints on the shape of the application or the hosting platform, constraining only those things that absolutely have to be constrained to make OWIN possible.
I wanted to extend these great OWIN concepts up to the next layer, and define a set of interfaces that place no unnecessary constraints on the shape of the middleware components whilst at the same time allowing middleware components to be switched out transparently in the same way that you can switch out the hosting service.
Using only the OWIN specification I can't use any session or authentication middleware I like and have it work with any output rendering framework I like because these things don't know how to talk to each other. In addition as a developer I have to understand all the dependencies bewteen middleware components from different sources to be able to configure a working application.
I think we can do much better than this. I want to be able to choose any middleware I want, and have something else build me an OWIN pipeline that will work. If I am missing something that is essential then tell me what I am missing and tell me what my options are.
Consider the following scenario: I have a UI and API way of accessing the functionallity of my web site. The UI and the API share functionallity at the model and business logic level and need shared caching, but they use different rendering frameworks. I want to build this with OWIN because OWIN is great! The problem is that I want forms authentication for the UI, and I want certificate based authentication for the API. I want the UI and the API share the same session mechanism. Each UI component and each API endpoint specifies whether it needs session or not, it also specifies the user permissions required to access the functionallity it provides. My UI is a composition built from multiple UI components.
Katana can do this I hear you say! But for me Katana missed the whole point of the open architecture that OWIN promised. Katana is an evolution of ASP.Net and as such is a huge suite of middleware components that work together but do not work with anything else. Sure Microsoft provided specific points of extensibility like creating your own view engine, but these things are extremely complex and it takes many hours to understand enough about the Katana ecosystem to extend it in any meaningful way. I don't think Katana is a good platform for everyone to use as a model for writing interoperable middleware components becuase it is full of details specific to the Microsoft implementation. In short I don't think Microsoft designed Katana to be the foundation of an open architecture for building middleware components, and I see that as a missed opportunity.
This project set out to define an open architecture for building middleware components that work together, and in the spirit of the original OWIN design it comprises mostly interfaces that do not place constraints on the shape of the middleware components.
Using this framework I can source UI components from other developers that know how to specify session and authentication without knowing which session provider or authentication provider I chose, and the session provider knows whether it needs to establish session or not without knowing anything about the middleware downstream. This is just one example of the class of problems that this framework solves.
This project mostly consists of interface definitions. These interfaces extend the original OWIN concept of not restricting the building blocks of the application by enforcing constraints on what their shape should be, whilst at the same time providing enough structure to allow different implementations of the same functionallity to be switched out without having impact elsewhere.
The areas of standardization covered by this project are: Configuring the OWIN pipeline to satisfy dependencies between middleware Defining routes and splitting/joining the OWIN pipeline Communication between OWIN middleware components
Note that this is a work in progress, and I would welcome contributions from as many other developers as possible. The more people who use this framework, the more useful it will be to everyone so please join in.
ExampleUsage.csproj is a project that demonstrates some of what is possible with this framework. It is by no means trying to be an exhastive list of what can be done, but just a few variations to give a flavour.
OwinFramework.Net40.csproj compiles to the DLL that gets installed from NuGet. This is the core framework itself and consists mainly of interfaces but also has an OWIN pipeline builder that resolves dependencies and provides routing. There is also a Net45 version of this project.
OwinFramework.Configuration.ConfigurationManager.csproj is distributed as an optional extra NuGet package that provides middleware configuration via the web.config file using the ConfigurationManager class. I only built the .Net45 version so far.
OwinFramework.Configuration.Urchin.Net40.csproj is distributed as an optional extra NuGet package that provides middleware configuration via the Urchin rules based configuration management system. There is also a Net45 version of this project.
UnitTests.csproj contains what you would expect!
OwinFramework.Mocks.Net40.csproj contains mock implementations of the OWIN Framework interfaces. You can use these mocks in your unit tests to mock the framework itself. There is also a >net 4.5 version of this project in the solution.
These are the next batch of NuGet packages that are in the pipeline: