Bloggers have uncovered an application for Windows 8 that blurs the line between Windows, the web, and mobile using a new architecture from Microsoft.

The application is called Modern Reader, Microsoft's own version of PDF Reader. According to bloggers Rafael Rivera and Paul Thurrott, who've been combing through leaked Windows 8 code and screenshots, it will be included with the yet-to-launch Windows 8.

The pair said that Modern Reader utilizes Microsoft's new AppX application package type.

AppX – or .appx as it is likely be written by coders – was identified by Thurrott in January, who said the Windows 8 and Office team are betting "very heavily" on it.

AppX sounds like the enabler for one of two expected UIs for Windows 8: the UI codenamed Mosh for tablets, which will do at least two things. It will introduce a tiled interface, making Windows 8 on tablets look more like Windows Phone 7 on smartphones. It will also let users download apps from Microsoft's Windows Marketplace.

AppX seems related to the application model for Windows 8 codenamed Jupiter.

Here's how All-About-Microsoft's Mary Jo Foley described Jupiter in January:

Jupiter is going to be a new user interface (UI) library for Windows, built alongside Windows 8. It will be a thin XAML/UI layer on top of Windows application programming interfaces and frameworks for subsystems like graphics, text and input. The idea is Jupiter will bring support for smoother and more fluid animation, rich typography, and new media capabilities to Windows 8 devices.

Blogger Long Zheng blogged that AppX is inspired by Silverlight's .xap files and notes that developers will need to specify a long list of possible attributes - more than required by Windows Phone developers. He notes that AppX is universal enough that it appears to work for native Win32 applications, framework-based applications like Windows Presentation Foundation and Silverlight, web applications, and games.

Thurrott says that Microsoft is already adding .appx to Visual Studio 2012. The apps themselves can be written in C#, Visual Basic, and C++.

Meanwhile, Microsoft has said it will release a beta for the next version of Silverlight - it's media player browser plug-in now demoted for HTML5 - at its MIX conference in Las Vegas, Nevada, next week.

Microsoft announced the news here, complete with a long winded justification of why Microsoft built Silverlight and plenty of talk about how Microsoft remains committed to Silverlight despite changing its priorities for media and content in the browser.

According to Microsoft, it will continue to support "scenarios that require plug-in based capabilities", and it will use MIX to talk about Silverilght on Windows Phone - where it's now the development environment. ®