There are some caveats to this approach the reader should be aware of. First, in this retrofitting example the transformations were performed by the browser but executing the transformations server-side has a couple of advantages. Server-side transformation reduces the burden on mobile devices, which have less processing, power, and memory capabilities than the server.
Second, XSLT’s roots in functional programming make it inaccessible to the average Web developer. It isn’t simply a matter of learning a new syntax. The recursive processing model of XSLT requires a new way of thinking that is unfamiliar to developers of imperative languages, especially developers from a design background who do not have formal training in computer science.
Finally, a larger challenge is that this technique works only for Web pages that are in XHTML (a flavor of HTML that is XML-compliant), because XSLT can transform only XML, not HTML. According to W3Techs, 55% of websites are in XHTML. While this is a majority, it still leaves out a large number of websites. In fact, for this retrofitting example, I worked around this limitation by running Hacker News’ HTML code through an HTML to XHTML converter.
In the next section, we’ll explore how the Tritium transformation language was built to address these issues.
In the example above, we’ve used transformations in the browser to create a responsive experience for an existing website, but conceptually the two approaches overlap. Because responsive Web design is itself about changing presentation across multiple screen sizes, transformations can help in that process as well. Instead of simply pairing different CSS styles to the same fixed HTML as in typical responsive design, we can leverage transformations to change the HTML across devices.
As we explored earlier, the ability to manipulate the HTML (which is missing from CSS alone) not only creates flexibility but actually improves the separation between presentation and content. As a result, maintainability becomes easier because the content is more semantic and less tied to layout. In essence, think of this as moving the breakpoints in responsive design to the transformation layer.
At Moovweb, we’ve leveraged these insights about transformations to implement a technique called responsive delivery, which draws inspiration from responsive Web design, RESS and adaptive design. With responsive delivery, transformations are used to adapt an existing website to different touch points, such as smartphones and tablets.