Database Reference
In-Depth Information
Hypertext Transport Protocol (HTTP): HTTP is the protocol used to transfer of
information over the WWW. It is characterized by a simply request-response structure
that represents interactions between a client (Web browser) and a Web server. It is
assumed that you are familiar with the Internet, basic Web page construction, Uniform
Resource Locators (URLs), domain names and other related issues.
Web Services Description Language (WSDL): The original authors of WSDL define
it as “an XML format for describing network services as a set of endpoints operating on
messages containing either document-oriented or procedure-oriented information”
[Ariba, 2001] WSDL can be construed as an interface definition language (IDL) with
bindings that clearly specify how the various components of a message are mapped.
WSDL messages are frequently transmitted as SOAP messages over HTTP.
Client-side Extensions: These add functionality to the Web browsers. Client-side
extensions are available in various forms. Following is a summary of the most commonly
encountered ones:
Plug-ins: A plug-in is an external application program that
is automatically invoked by the Web browser when required.
For example, a Web browser, upon receiving a PDF (portable
document format) document will invoke the available PDF-reader
on the host operating system.
Java : As you are no doubt aware, Java is a platform independent
programming language. Most operating systems have a Java
Virtual Machine (JVM), which allows Java code to execute on the
local machine (if there isn't a JVM in the operating system, this is
readily available from the Sun Microsystems Web site). Calls to Java
routines are often embedded in HTML pages. When a Web browser
encounters this, it invokes the local JVM to execute the code.
JavaScript: JavaScript is a Java-like scripting language (developed
by Netscape), but is much simpler. JavaScript code is often
embedded in Web pages. It is downloaded whenever the Web
page is activated, as well as on certain specific events (such as
loading of a specific page from the server, or a mouse-click, etc.)
Whenever the browser encounters this, it invokes the JavaScript
plug-in to execute this code.
ActiveX: ActiveX is Microsoft's alternative to Java. It works
perfectly in a Windows environment. Although possible in
other languages, C++ and Visual Basic are well known for their
facilitation of ActiveX controls.
 
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