Document developers and user agent designers are constantly discovering new ways to express their ideas through new markup. In XML, it is relatively easy to introduce new elements or additional element attributes. The XHTML family is designed to accommodate these extensions through XHTML modules and techniques for developing new XHTML-conforming modules (described in the XHTML Modularization specification). These modules will permit the combination of existing and new feature sets when developing content and when designing new user agents.
If your document is just pure XHTML 1.0 (not including other markup languages) then you will not yet notice much difference. However as more and more XML tools become available, such as XSLT for tranforming documents, you will start noticing the advantages of using XHTML. XForms for instance will allow you to edit XHTML documents (or any other sort of XML document) in simple controllable ways. Semantic Web applications will be able to take advantage of XHTML documents.
The old HTML behaviors would be achieved by XML stylesheets, rendering into HTML4 or XML events.
There were then a plethora of standards planned to augment XHTML with application level.
Quote (http://www.w3.org/TR/xhtml1/#why)
Document developers and user agent designers are constantly discovering new ways to express their ideas through new markup. In XML, it is relatively easy to introduce new elements or additional element attributes. The XHTML family is designed to accommodate these extensions through XHTML modules and techniques for developing new XHTML-conforming modules (described in the XHTML Modularization specification). These modules will permit the combination of existing and new feature sets when developing content and when designing new user agents.
Quote (http://www.w3.org/MarkUp/2004/xhtml-faq):
If your document is just pure XHTML 1.0 (not including other markup languages) then you will not yet notice much difference. However as more and more XML tools become available, such as XSLT for tranforming documents, you will start noticing the advantages of using XHTML. XForms for instance will allow you to edit XHTML documents (or any other sort of XML document) in simple controllable ways. Semantic Web applications will be able to take advantage of XHTML documents.
The old HTML behaviors would be achieved by XML stylesheets, rendering into HTML4 or XML events.
There were then a plethora of standards planned to augment XHTML with application level.
http://www.w3.org/standards/xml/components
Bindings in XForms for example, http://www.w3.org/TR/2009/REC-xforms-20091020/#ui-binding-ex...