Appendix E. Microformats: Extending (X)HTML

by Tantek Çelik

XHTML stands for the Extensible HyperText Markup Language. HTML 4 was also designed to be extended, albeit much more subtly. In the past few years, there has been a resurging interest in extending HTML and XHTML. XHTML was originally designed to be extended with other XML elements, in other namespaces. In practice, such extensions have yet to meaningfully materialize on the Web.

Instead, using extension mechanisms introduced in HTML 4, such as the class, id, and rel attributes, web designers, developers, and technologists have been extending the semantics of their HTML and XHTML documents. In the past couple of years, common patterns and conventions have emerged for using these mechanisms. Microformats are an effort to standardize these conventions and are specifically designed for ease of use by web authors and to leverage existing interoperable standards. By doing so, microformats have enabled the simple sharing of even more semantic content on the Web without having to learn a new language or duplicate content (either in comments or separate files).

This appendix introduces a few of the open microformats standards being developed by the microformats community. To learn more, visit the microformats.org community site.