One of the benefits of an RIA is that the application can smoothly transition from state to state without having to fetch a new page from the server and refresh the browser. By avoiding the constant refreshing of pages, the end-user's experience is more fluid and continuous, and is much the better for it. However, a browser's page-oriented treatment of the interface refresh has the advantage that an application's navigational state is always clearly coupled to a URL that can be bookmarked, emailed, and accessed via the browser's Back and Forward buttons.

The optional browser-history mechanism that ships with Flex 2 attempts to address this shortcoming, but its URLs are automatically calculated from the internal state of various components in the application which are assumed to represent the application's overall state. This has a number of problems:

• The application has no control over either the generation of these URLs (as states change) or the interpretation of previously generated URLs to which the browser is directed

• URLs are only coupled to specific UI components and cannot be mapped to more abstract notions of state</li>

• Generated URLs are opaque hashes with no documented encoding. Because of this, they cannot be understood by humans or generated by other programs external to Flex.

Enter UrlKit, which adds URL-mapping or "bookmarking" capabilities to Flex-based RIAs. While numerous others have provided solutions to this problem, what’s different in UrlKit is that it leverages your existing application logic and provides a way to declaratively code the different URL states.

Supported Browsers: UrlKit has been tested with Firefox 1.x, 2.x, Internet Explorer 6, Opera and Safari 2. IE7 is still an unknown quantity at this point.