IGP:FoundationXHTML primarily represents document and content structure and semantic properties with a controlled class attribute value grammar and nested property inheritance. All styling requirements are carried by stylesheets or device default capabilities, except for a few presentation issues for tables that are difficult for stylesheets.
For accessibility and the ultimate presentation "dumb-down", IGP:FoundationXHTML must present itself to a user in a web browser in readable and presentable manner without any stylesheets applied. This addresses both accessibility and construction ease. This rule also applies to generated content such as Tables of Content and Indexes.
For consistency and where possible content should be tagged into its correct location in the default flow for the style-less online presentation, and without consideration of other formats that can, want, or need to reflow content to different positions for various reasons.
Using stylesheets for presentation ensures the XHTML core is relatively simple and easy to work with. Every class attribute is available for as both a structural/semantic definition AND a presentation/processing target. This contributes to ease of designing, building and maintaining processors, generators, harvesters and format translators.
For advanced processing the core FX works the class attributes very hard with multiple selectors, pseudo-selectors, extended inheritance, counters, and paged media. Obviously not all display technologies can handle all of this. In fact there is no one technology that can handle all of the CSS 1-3 features.
Aggressive use of the latest standards ensures that the content product is both now and future ready and not compromised by past or proprietary formats. This is a core strength of IGP:foundationXHTML, it's tomorrow ready today. It works on the basis that it is easy to “dumb-down”, it is easy to “move-across”, but is it impossible to make it smarter unless the smart genes (detailed expressive tagging) are all in place.
This approach ensures maximum flexibility in presentation across changing content usage scenarios. This can be seen in IGP:Digital Publisher where the Writer (authoring/editing/tagging), Reader (Online interaction) and Print stylesheets are all significantly different, delivering different optimized user experiences from the same XHTML instantly and always.
The XHTML structures can be moulded and changed in many ways. The styles can be generated to match abilities of various platforms, devices (especially portable viewers) and technology generations.
Note: As the reading device landscape changes quite rapidly, some comments in this section may age and become irrelevant.
It is a content ownership disaster to create XML content of any type for a specific device. Devices change. Handling device limitations is the responsibility of the FX structure insofar as it is designed to be processed down to the capabilities of simple devices. This means the core content XML is always the best it can be.
For normal usage there is generally no requirement for XSL processing with FX. Processed FX uses the processing power closest to the end user for most of the heavy processing. This is usually the browser on a Users workstation. However in the case of portable devices and eBook Readers, the available processing power is very limited. In this case a format processor "dumbs down" the stylesheet, minimizes the number of style selectors, and splits the XHTML into device consumable chunks.
We are still in a world where not all platforms are equal. Many portable devices have limited processing power and memory. To DOM parse a complex document and maintain it in memory takes multiples of the file size, and that memory will probably not be available in a small device (at present anyway).
Additionally there are still simple devices that do not have the environment to display even a reasonable number of styles, and other devices that virtually ignore stylesheets completely.
Complex CSS stylesheets can consume memory and CPU resource and possibly slow down the users reading experience. This occurs mainly when text has to be “reflowed” because of a text sizing event.
Some small devices do not handle extensive linking well, fully linked index content is an example. Options must be available to address these issues, while ensuring the master XHTML is ready for more complex presentation as well.
At the same time that we need to be able to address device and format limitations, a real market for eContent is Online and variable content. Here both publishers and end users have high expectations of excellence and do not readily accept device/format limitations.
The same production strategies need to easily deliver the gamut of expectations from resource deprived mobile devices to the most sophisticated workstations and server rendering farms.
CSS-3 is pushing ahead at a remarkable rate for Online content and even print content. The web look of only a few years ago has largely gone, and online limitations are constrained only by MS IE's backward approach to standards compliance. The two open source browser engine giants, Mozilla and Webkit are pushing their presentation environments forward in coordination. This includes HTML 5 (XHTML 5) and the powerful canvas element and WebGL. Publishers of all types can look forward to a new media future that does not take more effort in authoring and editorial functions, but brings in new content value just through flexible presentation technologies.
Just some of the technologies available now, but not generally used for web sites because of browser compatibility issues are:
If you are a publisher, and your organization has a locked in MS IE policy it is time to get busy and change that policy. CSS is a significant part of the future of publishing and no publisher can afford not to know what is going on.
A good reference to track CSS-3 advances is www.css3.info. It's a little opinionated but it is authorative and an excellent user-friendly view on the world of advanced CSS.