TCP/IP Tutorial and Technical Overview - IBM Redbooks

computer, an AIX 5L or UNIX machine, or a mainframe, and the Web browser on
any client machine can understand the HTML tags and build the data stream to
display it on the target device. HTML tags describe basic elements of a Web
document, such as headers, paragraphs, text styles, and lists. There are also
more sophisticated tags to create tables and to include interactive elements,
such as forms, scripts, or Java applets.
After document writers and programmers have mastered HTML, those skills are
applicable to any operating system on any machine, provided that it has a Web
browser.
Because HTML supports hypertext, it allows document writers to include links to
other HTML documents. Those documents might be on the same machine as the
original, or they might be on a machine on another network on the other side of
the world; such is the power of HTML links.
Extensible Markup Language (XML)
Extensible Markup Language (XML) describes a class of data objects called
XML documents that are stored on computers, and partially describes the
behavior of programs that process these objects. XML is an application profile, or
restricted form, of SGML. The goal of XML is to enable generic SGML to be
served, received, and processed on the Web in the way that is now possible with
HTML. XML has been designed for ease of implementation and for
interoperability with both SGML and HTML.
16.4.2 Client-side dynamic content
The extension of functionality into the client has led to the development of
technologies to leverage dynamic content on the client’s side.
Programs and applets
When a Java program is started from inside an HTML (Web) page, it is called a
Java applet, as opposed to a Java program, which is executed from the
command line or otherwise on the local system. Applets are downloaded by the
Web browser from a server and, by definition, are somewhat limited in the way
they can use resources of the local system.
Originally, Java applets were not supposed to touch anything local (outside of its
Java virtual machine, or JVM), and could only communicate back to the server
from which it was downloaded. With Java 1.1, applets can be signed with
security keys and certificates and can therefore be authenticated. Therefore, an
applet can be authorized to access local resources, such as file systems, and it
can communicate with other systems.
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