The pages in the Web are stored and retrieved in HTML. This is a fairly modest, but incredibly powerful extension to SGML.
A very modest example of HTML is shown:
<TITLE> HIPPARCH </TITLE> <H1>HIPPARCH </H1> <body> <H2>HIPPARCH: High Performance Protocol Architectures </H2> <img src=./ec.gif> <p> HIPPARCH is an ESPRIT Basic project investigating High Performance Protocol Architectures using Integrated Layer Processing (ILP) and Application Layer Framing (ALF) principles. <UL> <LI> <a href="http://www.cs.ucl.ac.uk/staff/jon/hipparch/cfp.html"> Call For Papers for Fall Workshop </a> <LI> Partners include: <a href="http://www.ee.uts.edu.au/dml.html"> UTS</a>, <a href="http://zenon.inria.fr:8003/"> INRIA </a> and <a href="http://www.sics.se/"> SICS </a> <LI> Staff at UCL are <a href="http://www.cs.ucl.ac.uk/people/atanu.html"> Atanu Ghosh </a> and <a href="http://www.cs.ucl.ac.uk/staff/jon.html"> Jon Crowcroft </a> </UL> <p> We will add publications and deliverables to this page as they become available. <p> <a href="http://www.cs.ucl.ac.uk/research.html"> Other Research @ UCL CS </a>
As you can probably guess, commands are enclosed in angle-brackets <>, so that the HTML command <TITLE> means that the following text is part of the title.
Commands beginning </ are the end of the equivalent command. For example to say that the text ``This is the Page Heading'' should be a level one heading (the largest type of heading), the complete sequence is:
<H1>This is the Page Heading</H1>A break between paragraphs is denoted <P>. There is no need for a </P> afterwards because the end of a paragraph is obvious from the start the next paragraph, list, heading or whatever.
Strictly speaking a page should start <HTML> and should end </HTML>, but the HTML specification also says that clients should perform correctly without them, and so many people omit them. Similarly the header of a document (the bit containing the title) should begin with <HEAD> and end with </HEAD> and the body of a document should begin with <BODY> and end with </BODY>, but in practice this isn't essential. The HEAD and BODY commands are newer additions to HTML, which allow some of the fancier features to be used, but if you're not using these features, you can safely omit both.
Documents written in HTML are not WYSIWYG
- Mosaic and other WWW
clients will re-arrange the layout of your text so it fits properly on
whatever size display you try and display it on. So if you really
want to break a line at a specific place, you should use <P>,
or <br>,
rather than a carriage return, as Mosaic will remove the carriage
return and replace it with a space, and then break your line of text
at a point that is convenient for the current page width. Hence the
text:
<P>
This is another paragraph,
with a sentence
that is split over several lines.
Will get formatted as:
This is another paragraph, with a sentence that is split over several lines.
The most interesting feature of HTML is the inclusion of hyper-references, via the HREF command which allows us to place links in a document to other documents, or to other sources of other media. For example, I can directly reference other work in the midst of a document so that a browsing user can follow the link, look at the other work, and then come back and continue through my document. The examples of HTML above have examples of such links. They look like: <a href="http://www-server.bcc.ac.uk/home.html"> The Orignal University of London</a> .
HTML is being enhanced to HTML+ (to be renamed HTML 3.0) as we write. It might be assumed that the work doesn't need another markup language, but HTML is based on SGML anyway, and the enhancements are necessary to make the hyper-media data more presentable, but will not generally be used heavily within a single element in a single medium.