Recently there have been comments floating around the internet and around conferences that Microsoft's Silverlight needlessly uses XAML as its mark up language where it should have used SVG (Scalable Vector Graphics). The argument here is based on the idea that since SVG is a vector technology accepted in all web browsers except IE, Microsoft should have used it instead of XAML and then simply added support for SVG to IE. While this seams to some to be a valid criticism and a good point to some of the web standards world, it is absolutely groundless and carries no weight.
Silverlight can be viewed as a web extension of the Windows Presentation Foundation (WPF), a .NET 3.0 technology and not simply as a new web technology. As such, it makes sense that Silverlight uses XAML, not SVG. If Silverlight were based on SVG, then there would be a chasm between Silverlight and the .NET Framework, but as it stands Silverlight's use of XAML makes it part of the .NET family. In fact, it’s important to note that elements in XAML usually represent objects in the .NET Framework; this would simply not be possible in SVG. Therefore, by choosing to use XAML over SVG, Microsoft kept SVG pure by not add proprietary technology to it.
Standards advocates should be very satisfied with Microsoft's decision to start from scratch on this one. Standards, as they are normally referred to as, deal with standardization and thereby allow everyone to talk about the same technology without proprietary terminology or technology. If Microsoft sets an explicit syntax on a well-defined language, publicly states the specification for the language, and makes it a multi-platform language, then the world has basically the same result that a standard would have (this point will be hit again in a moment.) While it's true that "popular" doesn't make things right (something most people learn early in high school) and that statements about "most people" do not mean a single thing, having a well-defined technology set with a set specification does make it a first class technology.
Lastly, it should be noted that one of the primary purposes of using the web as a platform is to make something more accessible. People should be able to use any sufficiently advanced web browser to access a web page or web application anywhere on the entire Internet. Truly, even if an application is created in a corporate environment, if the technologies used are proprietary to any one specific web browser, the primary purpose of using a web browser is defeated and using a smart client would probably give a much richer experience and result. So, while it is true then that the use of proprietary technology, such IE specific content, defeats the entire purpose of using the web as a platform, if a technology is spread enough, is on enough platforms, and allows integration into their current environment (i.e. Firefox, Safari, Opera), it doesn't need to be a standard because it would achieve the same result as a standard. Flash is probably the best example of this.
In conclusion, there should not be much fuss about Microsoft's new "Flash-killer" using what some would view as private corporate technology. As long as there is support for Silverlight in Firefox, Opera, Safari on Windows, Mac OS X, and Linux and a seamless installer experience, there shouldn't be any problem with a rapid world wide adoption of this new technology. Hopefully Silverlight's adoption into the web as a de-facto standard will silence many forms of critisism about it and help prompt developers to do a better job of creating intranet and Internet solutions for muliple platforms and multiple web browsers.