Some of the most common relationships are represented in Figure 2.1.
Fig. 2.1 SGML and its derivatives—an example
Figure 2.1 shows an example of what the inheritance structure looks like. There are various other derivatives that have evolved and are still evolving, aligning with the World Wide Web Consortium (W3C) principle of being evolving and open. For example some of the specialized XMLs are MathML, CML (Chemicals XML), X3D (3D Graphics ML), etc.
HTML is the most common means of browser-based communication. The web as it exists today—being vibrant and open—is predominantly due to HTTP and HTML. We will focus on HTML ...