Pragmatics of Declarative Programming in Web Development

In contrast to traditional imperative approaches to scripting and Ajax, there is an emerging trend to provide declarative interfaces to user interface components. Currently, rich internet applications are built,for the most part, with open standards such as JavaScript, CSS and HTML. New HTML based technologies such as XForms, SVG and more are great examples of declarative approaches to RIA’s yet have not had much up take in the short time they have been around. Moreover, new proprietary declarative RIA frameworks from large companies such as Adobe’s Flex or Microsoft’s WPF/E and even Microsoft’s Ajax Framework (formerly Atlas) are increasingly trying to take market share from these open and standards based approaches.

However, rather than adopting a new technology into the Ajax stack or replacing it all together with with a proprietary solution, we can achieve rich, declarative approaches to Ajax that involve only the current Ajax stack and available frameworks. Undoubtedly, the benefit of a declarative approach to Ajax is huge – not only does it mesh well with the current HTML (definitive declarative programing) based sandbox, but it further removes the developer from any and all JavaScript, CSS and DOM browser inconsistencies. We will take a pragmatic look at the advantages and, importantly, drawbacks of declarative programming and compare and contrast declarative with imperative approaches.

Furthermore, we will discuss which approach has been adopted by the various frameworks and what the options are for developers both today and in the near future. Finally, we will demonstrate a practical approach to declarative Ajax by stepping through a complete code example that will identify many of the pitfalls associated with declarative Ajax in XHTML and across different browsers.