IT Assignments paper for IT Students and readers

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Website Design
BT0078 Part-2
By Milan K Antony

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Explain the architecture of the web page contents.
The basic web architecture is two-tiered and characterized by a web
client that displays information content and a web server that
transfers information to the client. This architecture depends on
three key standards: HTML for encoding document content, URLs for
naming remote information objects in a global namespace, and HTTP
for staging the transfer.
The common representation language for hypertext documents on the
Web. HTML had a first public release as HTML 0.0 in 1990, was
Internet draft HTML 1.0 in 1993, and HTML 2.0 in 1994. The
September 22 1995 draft of the HTML 2.0 specification has been
approved as a standard by the IETF Application Area HTML Working
Group. HTML 3.0 and Netscape HTML are competing next generations
of HTML 2.0. Proposed features in HTML 3.0 include: forms, style
sheets, mathematical markup, and text flow around figures. HTML is
an application of the Standard Generalized Markup Language (SGML
ISO-8879), an international standard approved in 1986, which specifies a
formal meta-language for defining document markup systems.
An IETF addressing protocol for objects in the WWW ("if it’s out
there, we can point at it"). There are two types of URIs, Universal
Resource Names (URN) and the Universal Resource Locators (URL).
URLs are location dependent and contain four distinct parts: the
protocol type, the machine name, the directory path and the file

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name. There are several kinds of URLs: file URLs, FTP URLs, Gopher
URLs, News URLs, and HTTP URLs. URLs may be relative to a
directory or offsets into a document.
An application-level network protocol for the WWW. Tim Berners-
Lee, father of the Web, describes it as a "generic stateless object-
oriented protocol." Stateless means neither the client nor the server
store information about the state of the other side of an ongoing
connection. Statelessness is a scalability property but is not necessarily
efficient since HTTP sets up a new connection for each request, which
is not desirable for situations requiring sessions or transactions. In
HTTP, commands (request methods) can be associated with particular
types of network objects (files, documents, network services).
Commands are provided for
· Establishing a TCP/IP connection to a WWW server,
· Sending a request to the server (containing a method to be applied
to a specific network object identified by the object’s identifier, and
the HTTP protocol version, followed by information encoded in a
header style)
· Returning a response from the server to the client (consisting of
three parts: a status line, a response header, and response data),
and
· Closing the connection.

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2.What are the requirements for internet connections?
Since Internet is a composite network of more than thousands of
discrete networks, each having its own rules and procedures, there
could be many different ways by which you can connect to the
Internet. To use the Internet you need three things:
1. A Computer
2. Client programs to run on your computer (one client for each
type of service you want to use).
3. A way to connect your computer to the Net so your clients can
service your request.
To start with, we need to go over the different types of Internet
connections. There are essentially three different types of connections
for accessing the services and resources of the Internet:
· Dialup Connections
· ISDN, ADSL, and Leased Line Connections
· Satellite Connections
To access the Internet via a phone line, the concept is: Connect your
computer to the telephone system using either a regular phone line
(with a modem) or an ISDN line (which requires special equipment).
To start work, you run a communication program to dial the phone
and establish a connection with a remote Internet host. Once the
connection is established, you log in to the server by typing your user
name and password. At this point, there are three possible types of

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dial-up connections:An alternative to a regular phone line is ISDN
(Integrated Services Digital Network) and Asymmetric Digital
Subscriber Line (ADSL) – a type of telephone service. ISDN and
ADSL allow the user to connect to another computer at a speed which
is much faster than even the fastest modem because it is digital.
Thus, if you are using a phone line connect your computer to the
Internet, you are better off with an ISDN or ADSL (not all phone
companies offer them) connection because it is digital and it is a lot
faster. These services can be run as fast as 128 kbps.If you have a
shell account type of access, what you all need is to become a
terminal on the computer of your ISP, thus the minimum possible PC
configuration with a VT-1 00 or equivalent type of terminal emulation
software can server your purpose well. In fact you may have a simple
dumb terminal to access such an account. The terminal emulation
software on PC is also widely available such as PROCOMM, etc. Please
choose emulation software which has KERMIT and ZMODEM file
download capability. A modem with error correction capabilities 9.6
kbps or better, and telephone line with capability to dial service
provider Local/STD are also required.It is the power of software
available for TCP/IP account which has made Internet so popular
these days. It is highly desirable that you have a GUI operating
system such as Windows on your desktop, if you are a TCP/IP
account holder. Typically, you would require a TCP/IP connection
establishing software and a Web-Browser to access this type of
account.

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A modem which best suits your pocket and is fastest to its class is
the right choice. Typically a 28.8 kbps modem is found to perform
best with Indian ISPsSuch software is now bundled with new operating
systems such as which are also called TCP/IP sockets. If you do not
have it along with your OS you can have third party socket software
such as Trumpet Winsock. It is important to run this software to get
connected to your ISP before you can do the browsing part.Web
browsers are the Client software (your machine is a client to ISP’s
server) which has various graphics capabilities to access the information
from the Internet. Modem Web Browsers are capable of browsing
WWW, Gopher sites, FTP sites and also provide facilities for e-mail.
Initially NCSA’s web browser Mosaic hit the market which actually made
the browsing popular. Now web browsers from Netscape and from
Microsoft are the user’s choice. You can get hold of any such browser
and start browsing the Net.
3. Explain <frameset> tag and its attributes.
The browser display window can be used to display more than one
document at a time. The window can be divided into rectangular
areas, each of which is a Frame. Each frame is capable of displaying
its own document.

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The content of a frame is specified with the <frame> tag, which can
appear only in the content of a frameset element. The content of a
frame is specified as the value of the src attribute in the <frame>
tag.
Example:
<frame src = “apples.html” >
If the <frame> tag has no src attribute, the browser displays an
empty frame. If the content of a frame doesn’t fit into the given
frame, scroll bars are implicitly included. If you want a frame to
have scroll bars, regardless of the size of its content, the <frame>
attribute scrolling can be set to yes. If a <frame> tag includes a
name attribute, the content of its associated frame can be changed
by the selection of a link in some other frame that specifies that
name.
The <frameset> tag and attributes
The number of frames and their layout in the browser window are
specified with the <frameset> tag. A frameset element takes the place
of the body element in a document. A document has either a body or
a frameset but cannot have both.
The <frameset> tag must have either a rows or a cols attribute, and
they often have both. The rows attribute specifies the number of
rows of frames that will occupy the window. There are 3 kinds of

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values for rows: numbers, percentages, and asterisks. Normally, two
or more values, separated by commas, are given in a quoted string.
When a number is used as a value, it specifies the height of one row
in pixels. A percentage is given as a number followed immediately by
percent sign. When used, a percent value specifies the percentage of
the total browser window height that a row should occupy. When an
asterisk is used as the value of rows, it means the remainder of the
window height.
Examples:
<frameset rows = ”200, 300, 400”>
<frameset rows = “22%, 33%, 45%”>
<frameset rows = “22%, 33%, *”>
The cols attribute is very much like the rows attribute, except that it
specifies the number of columns of frames. For example, the
following tag specifies that the window is to have six frames in three
equal-height rows and two columns.
<frameset rows = 33%, 33%, 33%” cols = “25%, *”>
4. With an example explain the need for CDATA section in

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XML.
CDATA Sections are used to escape blocks of text containing
characters which would otherwise be recognized as markup. The
content of a character data section is not parsed by the XML parser,
so it cannot include any tags. The form of a character data section
is as follows:
<! [ CDATA[content ] ] >
For example, instead of using the line “the last word of the line is
&gt;&gt;&gt; here &lt;&lt;&lt” the following line could be used:
<! [ CDATA [The last word of the line is >>> here <<<] ] >
5. Explain the Union and List data types in XML.
List datatypes are special cases in which a structure is defined within
the content of a single attribute or element. The xs:list element is
used to define list of items. The definition of a list datatype can be
done by embedding an xs:simpleType element:
<xs:simpleType name="myIntegerList">
<xs:list>
<xs:simpleType>

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<xs:restriction base="xs:integer">
<xs:maxInclusive value="100"/>
</xs:restriction>
</xs:simpleType>
</xs:list>
</xs:simpleType>
This datatype can be used to define attributes or elements that
accept a whitespace-separated list of integers smaller than or equal
to 100.
List datatypes have their own value space that can be constrained
using a set of specific facets that is common to all of them. These
facets are xs:length, xs:maxLength, xs:minLength, xs:enumeration and
xs:whiteSpace. The unit used to measure the length of a list type is
always the number of elements in the list.
Derivation by union allows defining datatypes by merging the lexical
spaces of several predefined or user datatypes. The xs:union element
is used for defining the union of different types. The definition of a
union datatype can be done by embedding an xs:simpleType element:
<xs:simpleType name="myIntegerUnion">
<xs:union>
<xs:simpleType>
<xs:restriction base="xs:integer"/>
</xs:simpleType>
<xs:simpleType>
<xs:restriction base="xs:NMTOKEN">
<xs:enumeration value="undefined"/>
</xs:restriction>

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</xs:simpleType>
</xs:union>
</xs:simpleType>
Now the myIntegerUnion has the merged type of meaning given in the
example.