Executable Content - HTML and XHTML: The Definitive Guide - page 735

12.1. Applets and Objects
Applets represent a shift in the basic model of web communications. In
most other web applications, servers perform most of the computation-
al work, client browsers being not much more than glorified terminals.
With applets, web technology shifts to the client, distributing some or all
of the computational load from the server to the client computer and its
browser.
Applets also represent a way of extending a browser's features without
forcing users to acquire new browsers, as is the case when developers
implement new tag and attribute extensions to HTML. Nor do users have
to acquire and install a special application, as is required for helper or
plug-in applications. [*] This means that once users have a browser that
supports applets (all the currently popular ones do), you can deliver ap-
plets directly to the browser, including display and multimedia innova-
tions.
[*] Actually, Internet Explorer 6 users must download and install Java support. Read on for details.
12.1.1. The Object Model
Java-based appletsweb page-referenced programs retrieved from a net-
work server and executed on the user's client computerare an example
of what the HTML 4 and XHTML standards call inclusions . As with images,
the browser first loads the HTML document, then examines it for inclu-
sionsadditional, separate, and discrete content that the client browser is
to handle. A GIF image is one type of inclusion. A .wav sound file, an
MPEG movie, and a Java-based clock program are other types.
The HTML 4 and XHTML standards generally call the inclusion contents
objects . In fact, in your document you may identify and load nearly any
object file over the network through a universal <object> tag, discussed
in detail shortly in section 12.2.1 .
Once the object has been downloaded, the standards dictate that the
browser somehow render the object, by internal or external mechanisms.