Contrary to what has already been written elsewhere, XML is not the successor of HTML. XML is not the future of HTML. XML is not a replacement for HTML. XML and HTML are two distinct languages!
There is only one similarity between the two: the SGML language. The only common point between HTML and XML is that they are both from the same mother or Standardized Generalised Markup Language (SGML). SGML is the language of choice in the workplace for all that concerns electronic document management.
They are thus both of markup languages. They also have common characteristics that are inherited from SGML such as carrying on the Web data in text mode (plain text), compatible with any software platform. In summary XML and HTML are both are derived from SGML with whom they share common characteristics, such as working with tags, being platform independent and being in text mode.
Regarding differences, there are many between HTML and XML. HTML and XML are different in very many points, some of which relate to the essence of language. XML describes, structures and exchange data while HTML only displays data. XML is extensible and allows users to create their own tags based on the processed data.
Whereas HTML tags are predefined and therefore fixed. Here are the main features of XML. XML describe, structures, stores and exchange data. XML is a language generator (a metalanguage).Besides PCs, XML is intended as an appropriate tool for mobile, tablets, etc. For XML, W3C has restarted with a blank page and set up a new highly structured language.
XML is a strict language whose writing must be rigorous. Next are HTML features. HTML displays data through a browser. HTML is a static normalized language for publication on the Web. HTML is designed primarily for PC type computers. HTML with version 4.0 has reached the end of its evolution and became a hybrid and finally unstructured language.
HTML became very permissive because of newer browsers Finally let’s talk about HTML, XML and XHTML. XHTML is itself the successor to HTML. But it is also one of the children generated by XML. In short, to do some cleaning in the excesses of HTML over the various versions, the W3C has developed the XHTML that is in fact a reformulation of HTML 4.0 agreeing with the syntax and rules of XML.