Next Generation Internet:
The "Fourth Tier" Is Born - Internet/Web/Online Service
Information
Solving the
problem of disparate content types
Web content
began as static HTML pages and evolved to include client-side scripting,
proprietary content technologies, and application programming interfaces.
HTML has
remained the basis of all Web content-until now. We are about to witness the
revolutionary move of content from HTML to XML (Extensible Markup Language).
XML is a set of
rules for defining a document using tags in a self-described vendor- and
platform-neutral manner.
XML has
numerous advantages over HTML. It is easily transformable and can describe any
type of content.
Most
RecentTechnology Articles
HTML is a
rendered presentation of data for a specific set of clients (namely HTML-based
browsers), while XML can be data, its presentation, or a combination of both.
Metaphorically
speaking, HTML is a picture of a 3D object (Data, Presentation, and Flow Logic)
while XML is the 3D object itself.
Viewing an HTML
object from a different perspective will produce a fuzzy picture at best
because the object's entire data set is unavailable.
Cell phones,
PDAs, or embedded devices may have problems with HTML, which often has
extraneous or missing data.
Content in XML
can be transformed into a wide range of other content (like voice based
content) and made available to a wider range of devices (like digital cell
phones).
XML content can
be rendered in one way for cell phones (like WML for WAP) and in another way
for PC-based browsers (like XHTML).
The Complexities Of
Content
Content, more
complex than ever before, is currently provided by a variety of servers. It
exists in three distinct formats: data, audio (including voice), and visual
(including video).
Each content
type requires different mechanisms and systems for storage, processing, and
serving.
Content
combinations depend on user specifications, device capabilities, and available
content. Configuring the combination correctly is a complex process and is not
accounted for in the current development model.
Today's systems
solve only one problem: data. Audio and visual components must be integrated
and content mixtures served to clients must be synchronized.
The variety of
Internet clients has multiplied considerably.
Five years ago,
users only expected to access content from different PC browsers.
Today users
expect to tap into the same content from multiple devices with vastly different
capabilities.
These devices
range from cell phones to PDAs to web browsers. Each client can process
different amounts and combinations of each type of data. Web browsers, for
example, typically have a keyboard/mouse/monitor interface while cell phones have
a phonepad/voice interface. Hybrid devices combine the capabilities of devices:
PDAs have cell phones integrated into them and cell phones possess many PDA
capabilities.
When building
today's systems, future requirements must be considered, including content
form.
Most audio and
video systems have switched from analog to digital. Most digital, visual, and
aural based content is served in proprietary formats.
There has been
no equivalent to non-proprietary HTTP until recently, with the development of
XML.
Audio, data,
and video content can be described by metadata in XML.
Clients can
easily process data if video or audio streams are wrapped inside XML with some
meta data about the stream.
VoiceXML, for
example, allows voice-based content to be described by XML, encapsulating the
data concerning the content.
This data can
then be used to "introduce" the content to any client wanting to use
it.
Content can be
customized at run-time using an XML description of the client, user settings,
and content structure.
Approaching
content in this way gives birth to a new software layer separating the user
interface and the application server (the middle-tier).
This layer
enables us to author content once using the new presentation layer: then the
formats and logical flows required for various clients can be created. This new
system will separate the data, presentation, and logic of the user interface.
The Move From Three-Tier To Four-Tier
Architecture
Three-tier
architecture has been the prevailing design for Internet systems during the
past few years. In this design, there are three primary components:
- Database,
- Application server, and
- Client.
Three-tier
architecture was considered an evolutionary step over the client server model.
It removed
business logic from the client and the database and placed it into an
application server.
It became
responsible for the processing work that implemented the business logic in the
system.
It enabled
systems to scale larger and become more reliable by implementing various forms
of fail-over at a lower cost.
By clearly
defining an API (Application Programming Interface) at each tier in the
architecture, it allowed for a more sophisticated development cycle.
System
development could now be broken down and distributed among three groups:
database engineers, software engineers, and user interface developers. New
features could be added in a faster, more methodical way.
No comments:
Post a Comment