I get the Silverlight vs. Ajax question all the time, whether it is at a conference, over email, or over on discussion forums. In the interest of seeding a broader discussion, and hearing what other people think, I thought this would be an interesting blog post, along with the side benefit of having a ready-made answer the next time the topic comes up.
There have been a number of blog posts pitching Ajax vs. RIA (whether its Flash or Silverlight) such as this one here. Personally, I think Ajax and Silverlight complement each other, and the "vs." is a bit misplaced. Furthermore, the way I see it, there is a continuum, with a number of sweet spots representing specific classes of applications. This perspective is perhaps directly reflected in the makeup of the UIFX team that I work on at Microsoft - the team is spread across ASP.NET, Ajax, Silverlight and RIA frameworks all at once actively working on cool stuff in each of these areas (i.e. lots to look forward to).
Reach and Rich
The diagram represents a spectrum of application development approaches and technologies/platforms with increasing reach on one end, and increasing capabilities on the other. Applications have distinct scenarios and correspondingly gravitate toward a sweet spot. Some apps lie squarely on the left, with the need to first and foremost prioritize universal reach. At the same time, some apps have experience or functionality as the high order bit, where it is necessary to leverage a more capable platform, even if it means somewhat reduced reach. Still, the best apps will probably be those that leverage multiple front-end options to follow the user, with a common back-end (sort of a software and a service model).
One thing is sure - users are expecting more, and apps are trying to differentiate by meeting them. For example, the Ajax hype has given way to broad mainstream and pragmatic use of the technology (hence I call the older style of Web apps as "Classic" in the diagram).
RIA Islands
At the same time, the reality is a number of applications are no longer "pure" Ajax, i.e. just HTML and Script-based. Ajax applications are increasingly relying on plugins such as Silverlight, Google Gears, and Flash to incrementally enrich the experience they can offer (ideally, in a manner such that they gracefully degrade). These plugins let Ajax applications do interesting things like use local storage, access user's files, integrate rich media and vector graphics, background processing etc. Just like ASP.NET server controls make it quite easy to incorporate Ajax functionality, they are also nicely positioned to simplify the "Islands of Silverlight" scenario. Imagine a data-bound server control that renders a Silverlight chart, and degrades to a static image dynamically rendered on the server without requiring the app developer to learn several new technologies. I've spoken on this at recent conferences, and will be blogging more on this end. Wilco blogged about Silverlight Interop to cover the use of Silverlight to implement HTML code-behind and creating a better file uploader for Ajax apps.
Trends
The second thing that is also interesting about the diagram are the trends in effect. The reach platform, starting to be referred to as the Open Web by some, is bound to get richer in terms of the execution engine, the presentation stack, and its framework capabilities. HTML 5 promises to improve some core pieces of the browser-based platform, and all the browsers (yes, that includes IE) are already stepping up to improving the state of the art in their next versions. The interesting question is when we will see ubiquity around the next batch of incremental improvements like the ubiquity of XMLHTTP that fueled the Ajax wave a couple or so years ago. RIA technologies are becoming more ubiquitous, and starting to become a viable or required choice for development in the next generation of Web apps. Over time as what is considered "rich" today gets commoditized by the reach platform, the platforms on the right need to constantly redefine themselves by finding new ways and value offerings in order to differentiate, which always keeps them interesting and in the forefront. It's a constant tug-of-war ... and it doesn't seem like either Ajax or the RIA approach is going to all out win any time soon.
A .NET Theme
So if you agree, the world isn't Ajax vs. RIA, but is rather Ajax and RIA (and Desktop), and there is room for them to co-exist, the final thing I'll point out is how the Microsoft platform plays out in this space. Clearly, the consistent theme across the board is .NET and managed code, which allows developer skills, as well as in many cases, common code that can be shared and leveraged as apps transition or grow. Ray Ozzie spoke to this when referring to connected development at MIX 08. We have .NET on the server providing that common backend, .NET on Web/Ajax front with ASP.NET and even . NET-flavored scripting with technologies like Script#, and of course, .NET on the client with WPF. Silverlight 2 brings .NET to the RIA space. In fact, the simple introduction of managed code into the browser is perhaps one of the most eagerly anticipated feature.
The fun, and simultaneously challenging thing, is working on the multiple sweet spots along the current application platform spectrum, balancing the feature set, and making sure we have messaging for how they evolve, complement, and differentiate to address specific scenarios at the same time.
Posted on Tuesday, 4/8/2008 @ 9:03 AM
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Silverlight