Knowledge World: B.Sc. IT BT0078 (Semester 3, Website Design) Assignment

Spring 2012

Bachelor of Science in Information Technology (BScIT) – Semester 3

BT0078 – Website Design – 2 Credits (Book ID: B1005)

Assignment Set – 1 (30 Marks)

1. What are the requirements for an internet connection?

Ans.- You have to have a modem, a phone line / LAN cable wire/ and a wireless router (if you plan to use wireless connection). Make sure you have an ISP (internet service provider) If you would like to get access to the internet at home, you'll need an Internet Service Provider (ISP) and a modem to connect to the ISP. ISPs often provide a device called a router to let you share an internet connection over a local area network, which means more than one computer in your house can use the broadband connection at the same time. The devices are connected with cables and a hub or switch.
A good place to start looking for an ISP is the Internet Service Provider Association (ISPA). Although this is a voluntary body it's recognized by government for its knowledge and expertise. All ISPs listed on the ISPA site have agreed to certain rules and standards set by the ISPA. This means you can be confident an ISP listed by ISPA has good business practice.
Similarly, you might find it helpful to get recommendations from friends who have an ISP as there is no better substitute for getting a recommendation from someone you trust. If you are going to look for the ISP on your own try to get as much information as you can about what they offer.

2. Briefly explain the transparent graphics.

Ans.- Transparency is possible in a number of graphics file formats. The term transparency is used in various ways by different people, but at its simplest there is "full transparency" i.e. something that is completely invisible. Of course, only part of a graphic should be fully transparent, or there would be nothing to see. More complex is "partial transparency" or "translucency" where the effect is achieved that a graphic is partially transparent in the same way as colored glass. Since ultimately a printed page or computer or television screen can only be one color at a point, partial transparency is always simulated at some level by mixing colors. There are many different ways to mix colors, so in some cases transparency is ambiguous. In addition, transparency is often an "extra" for a graphics format, and some graphics programs will ignore the transparency.

Transparent Pixels: One color entry in a single GIF or PNG image’s palette can be defined as "transparent" rather than an actual color. This means that when the decoder encounters a pixel with this value, it is rendered in the background color of the part of the screen where the image is placed, also if this varies pixel-by-pixel as in the case of a background image.

Applications include:

· An image that is not rectangular can be filled to the required rectangle using transparent surroundings; the image can even have holes (e.g. be ring-shaped)

· In a run of text, a special symbol for which an image is used because it is not available in the character set, can be given a transparent background, resulting in a matching background.

The transparent color should be chosen carefully, to avoid items that just happen to be the same color vanishing.

Even this limited form of transparency has patchy implementation, though most popular web browsers are capable of displaying transparent GIF images. This support often does not extend to printing, especially to printing devices which do not include support for transparency in the device or driver. Outside the world of web browsers, support is fairly hit-or-miss for transparent GIF files.

3. Explain the various tags used in Table.

Ans.- The <table> tag defines an HTML table. A simple HTML table consists of the table element and one or more tr, th, and td elements. The tr element defines a table row, the th element defines a table header, and the td element defines a table cell.

Example:

<tr>

<th>Month</th>

<th>Savings</th>

</tr>

<tr>

<td>January</td>

</tr>

</table>

The <th> tag defines a header cell in an HTML table.

An HTML table has two kinds of cells:

· Header cells – contains header information (created with the th element)

· Standard cells – contains data (created with the td element)

The text in a th element is bold and centered.

The text in a td element is regular and left-aligned.

Example:

<tr>

<th>Month</th>

<th>Savings</th>

</tr>

<tr>

<td>January</td>

</tr>

</table>

The <tr> tag defines a row in an HTML table.

A tr element contains one or more th or td elements.

<tr>

<th>Month</th>

<th>Savings</th>

</tr>

<tr>

<td>January</td>

</tr>

</table>

The <td> tag defines a standard cell in an HTML table.

An HTML table has two kinds of cells:

· Header cells - contains header information (created with the th element)

· Standard cells - contains data (created with the td element)

The text in a th element is bold and centered.

The text in a td element is regular and left-aligned.

Example:

<tr>

<th>Month</th>

<th>Savings</th>

</tr>

<tr>

<td>January</td>

</tr>

</table>

The <caption> tag defines a table caption.

The <caption> tag must be inserted immediately after the <table> tag. You can specify only one caption per table. Usually the caption will be centered above the table.

Example:

<caption>Monthly savings</caption>

<tr>

<th>Month</th>

<th>Savings</th>

</tr>

<tr>

<td>January</td>

</tr>

</table>

4. Explain the Domain Name System and DNS servers.

Ans.- The DNS translates Internet domain and host names to IP addresses. DNS automatically converts the names we type in our Web browser address bar to the IP addresses of Web servers hosting those sites. DNS implements a distributed database to store this name and address information for all public hosts on the Internet. DNS assumes IP addresses do not change (are statically assigned rather than dynamically assigned).The DNS database resides on a hierarchy of special database servers. When clients like Web browsers issue requests involving Internet host names, a piece of software called the DNS resolver(usually built into the network operating system) first contacts a DNS server to determine the server's IP address. If the DNS server does not contain the needed mapping, it will in turn forward the request to a different DNS server at the next higher level in the hierarchy. After potentially several forwarding and delegation messages are sent within the DNS hierarchy, the IP address for the given host eventually arrives at the resolver, that in turn completes the request over Internet Protocol. DNS additionally includes support for cachingrequests and for redundancy. Most network operating systems support configuration of primary, secondary, and tertiary DNS servers, each of which can service initial requests from clients. Internet Service Providers (ISPs) maintain their own DNS servers and use DHCP to automatically configure clients, relieving most home users of the burden of DNS configuration.

5. Explain the use of client-side image maps.

Ans.- Image maps aren’t as bad as they seem, at least if you use a client side image map using HTML rather than a CGI program. Now you need to put the image on the page. To do this, you use the image tag, but with a new attribute: usemap.

<img src="eximap1.gif" width="200" height="40" border="0" alt="image map" usemap="#mymap" />

The usemap="#mymap" command tells the browser to use a map on the page, which is named "mymap". Notice how it uses the "#" symbol in front of the map name. Also notice that we defined the width and height of the image. This need to be done so we can use coordinates later on when we define the map. Speaking of that, let’s see how to define the map. For this map, we would place the following code somewhere on the page.

Now you can see where the usemap="#mymap" from the <img> tag comes from. The name of the map is "mymap". Now, let’s look at what all of this means:

<map name="mymap" id="mymap">

This defines your image map section, and gives the map a name. This map is named "mymap" In XHTML, the id attribute is required rather than name. If you are using XHTML transitional, both the name and id can be used.

<area shape="rect" coords="0,0,99,40" href="table1.htm" alt="Tables" />

The area tag defines an area of the image that will be used as a link. The shape attribute tells the browser what shape the area will be. To keep it simple, I only used "rect", which stands for rectangle. The cords attribute is where we define the edges of each area. Since it is a rectangle, we will use two sets of coordinates. The first set defines where to start the rectangle, where the top-left edge of the rectangle will be. Since this rectangle starts at the top-left edge of the image, the coordinates are (0 pixels, 0 pixels). The second two numbers define where to end the rectangle. This will be the lower-right edge of the rectangle. Remember that the total image size was 200×40. We want the lower-right edge of this rectangle to be halfway across the image and at the bottom of the image. Going across, half of 200 is 100, but we use 99 here because 100 can only be used once. We will use it in the second rectangle here. Of course, 40 pixels take us to the bottom of the image. So the lower-right corner of this rectangle will be 99 pixels across the image, and 40 pixels (all the way) down the image. And now the easy part: The href attribute is used to tell the browser where to go when someone clicks someplace on that rectangle. Put the URL of the page you want to go to in there, and the first rectangle is set up! The alt attribute allows you to define alternate text for that area.

<area shape="rect" coords="100, 0, 200, 40" href="frame1.htm" alt="Frames" />

Basically the same as the previous area tag, but it is for our second rectangle. We start where the other one left off, but back at the top of the image. Since the right edge of the last rectangle was at 99 pixels across, we start this one at 100 pixels across. And since this will be the upper-left of the second rectangle, we start it at 0 pixels down the image (the top!). We end this rectangle where the image ends, so the lower-right coordinate here is pretty nice- (200, 40), the size of the image!

<area shape="default" href="http://www.pageresource.com"
alt= "Home">
The default is not really a new shape; it just covers anything that may have been left out. We didn’t leave out anything in this map, but if we had, this would be the URL someone would go to if they clicked on any area we did not define earlier.

</map>
This ends the map section!

Now, you can use other shapes besides rectangles, but those are a lot tougher to code by hand.

Spring 2012

Bachelor of Science in Information Technology (BScIT) – Semester 3

BT0078 – Website Design – 2 Credits (Book ID: B1005)

Assignment Set – 2 (30 Marks)

1. Explain the architecture of the web page contents.

Ans.- The World Wide Web has succeeded in large part because its software architecture has been designed to meet the needs of an Internet-scale distributed hypermedia application. The modern Web architecture emphasizes scalability of component interactions, generality of interfaces, independent deployment of components, and intermediary components to reduce interaction latency, enforce security, and encapsulate legacy systems.

Web Architecture

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

HTTP for staging the transfer.

HyperText Markup Language (HTML)

HyperText Markup Language is the predominant markup language for web pages. HTML is the basic building-blocks of webpages. A markup language is a set of markup tags, and HTML uses markup tags to describe web pages.

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. 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.

HTML is written in the form of HTML elements consisting of tags, enclosed in angle brackets (like <html>), within the web page content. HTML tags normally come in pairs like <h1> and </h1>. The first tag in a pair is the start tag, the second tag is the end tag (they are also called opening tags and closing tags). The correct structure for an HTML document starts with <HTML><HEAD> (enter here what document is about) <BODY> and ends with </BODY></HTML>. All the information you'd like to include in your Web page fits in between the <BODY> and </BODY> tags.

HTML Example

The purpose of a web browser is to read HTML documents and compose them into visual or audible web pages. The browser does not display the HTML tags, but uses the tags to interpret the content of the page. HTML allows for embedding of images, sounds, video streams, form fields and simple text formatting.

Universal Resource Identifier (URI):- In computing, a Uniform Resource Identifier (URI) is a string of characters used to identify a name or a resource on the Internet. Such identification enables interaction with representations of the resource over a network (typically the World Wide Web) using specific protocols. Schemes specifying a concrete syntax and associated protocols define each URI.

One can classify URIs as locators (URLs), or as names (URNs), or as both. A Uniform Resource Name (URN) functions like a person’s name, while a Uniform Resource Locator (URL) resembles that person’s street address. In other words: the URN defines an item’s identity, while the URL provides a method for finding it.

Uniform Resource Identifier (URI)

A URL is a URI that, in addition to identifying a network-homed resource, specifies the means of acting upon or obtaining the representation: either through description of the primary access mechanism, or through network “location”. A Uniform Resource Name (URN) is a URI that identifies a resource by name, in a particular namespace. One can use a URN to talk about a resource without implying its location or how to access it. The resource does not need to necessarily be network homed.

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.

HyperText Transfer Protocol (HTTP)

The Hypertext Transfer Protocol (HTTP) is a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web.

HTTP functions as a request-response protocol in the client-server computing model. In HTTP, a web browser, for example, acts as a client, while an application running on a computer hosting a web site functions as a server. The client submits an HTTP request message to the server. The server, which stores content, or provides resources, such as HTML files, or performs other functions on behalf of the client, returns a response message to the client. A response contains completion status information about the request and may contain any content requested by the client in its message body.

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).

2. Explain the usage of internal and external DTDs in XML.

Ans.- A Document Type Definition (DTD) defines the legal building blocks of an XML document. It defines the document structure with a list of legal elements and attributes.

A DTD can be declared inline inside an XML document, or as an external reference.

Internal DTD Declaration

If the DTD is declared inside the XML file, it should be wrapped in a DOCTYPE definition with the following syntax:

<!DOCTYPE root-element [element-declarations]>

Example XML document with an internal DTD:

<?xml version="1.0"?>
<!DOCTYPE note [
<!ELEMENT note (to,from,heading,body)>
<!ELEMENT to (#PCDATA)>
<!ELEMENT from (#PCDATA)>
<!ELEMENT heading (#PCDATA)>
<!ELEMENT body (#PCDATA)>
]>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend</body>
</note>

Open the XML file above in your browser(select "view source" or "view page source" to view the DTD)

The DTD above is interpreted like this:

!DOCTYPE notedefines that the root element of this document is note

!ELEMENT notedefines that the note element contains four elements: "to,from,heading,body"

!ELEMENT todefines the to element to be of type "#PCDATA"

!ELEMENT fromdefines the from element to be of type "#PCDATA"

!ELEMENT headingdefines the heading element to be of type "#PCDATA"

!ELEMENT bodydefines the body element to be of type "#PCDATA"

External DTD Declaration

If the DTD is declared in an external file, it should be wrapped in a DOCTYPE definition with the following syntax:

<!DOCTYPE root-element SYSTEM "filename">

This is the same XML document as above, but with an external DTD (Open it, and select view source):

<?xml version="1.0"?>
<!DOCTYPE note SYSTEM "note.dtd">
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

And this is the file "note.dtd" which contains the DTD:

<!ELEMENT note (to,from,heading,body)>
<!ELEMENT to (#PCDATA)>
<!ELEMENT from (#PCDATA)>
<!ELEMENT heading (#PCDATA)>
<!ELEMENT body (#PCDATA)>

Q3. Explain <frameset> tag and its attributes.

Ans.- Hyper Text Markup Language (HTML) is composed by a set of elements that are the basis of its structure. Elements are designed to provide tools to authors and give special information that will be used to compute the final representation of it. This means that where a tag is defined in the HTML code, something will happen in the representation of that document, that may be visual or not.

Attributes give certain characteristics to a tag (e.g., height, width, color, etc.), sometimes very important, that will finally set how the tag must be interpreted. For example, the HTML a tag inserts a link in an HTML document (a way to go from the actual document to another resource, usually with a click), but the real attribute establish which is the relationship between the actual document and the destination resource.

Frame:

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. The HTML frame is a powerful feature that enables a web page to be broken into different unique sections that are related but can be operated independently without depending on each other.

The <frameset> tag

The HTML frameset tag divides the available space in rectangular subspaces, where an individual HTML document can be loaded for each through the HTML frame tag.

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 is supported in all major browsers like Internet Explorer, Firefox, Opera, Google Chrome & Safari.

<frameset> tag attributes

Attribute	Value	Description
cols	pixels % *	Specifies the number and size of columns in a frameset
rows	pixels % *	Specifies the number and size of rows in a frameset

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 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:

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.

A simple example is dividing the screen in two columns, the first with 250 pixels of width and the second with all the remaining space.

There are unlimited possibilities to divide the screen in frames. Frames can be nested which allows authors to subdivide each one of the frames. Frames are subdivided by replacing a single frame by a frameset.

And there are more possibilities of nesting frames. For example if the "index.html" file in the example above is a frameset document, this will make new divisions to the "content" frame.

Frame Construction

Consider the following example.

<html>

</frameset>

</frameset>

</html>

This example creates totally 4 frames. First 2 vertical frames will be created.

Within first vertical frame two horizontal frames will be created. Within second vertical frame two vertical frames will be created.

Standard Attributes

The <frameset> tag supports the following standard attributes:

Attribute	Value	Description
class	classname	Specifies a classname for an element
id	id	Specifies a unique id for an element
style	style_definition	Specifies an inline style for an element
title	text	Specifies extra information about an element

Event Attributes

The <frameset> tag supports the following event attributes:

Attribute	Value	Description
onload	script	Script to be run when a document load
onunload	script	Script to be run when a document unload

4. With an example explain the need for CDATA section in XML.

Ans.- CDATA, means character data or (Unparsed) Character Data, is used for distinct, but related, purposes in the markup languages SGML and XML. The term indicates that a certain portion of the document is general character data, rather than non-character data or character data with a more specific, limited structure.

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. All tags and entity references are ignored by an XML processor that treats them just like any character data. CDATA blocks have been provided as a convenience measure when you want to include large blocks of special characters as character data, but you do not want to have to use entity references all the time.

In an XML document or external parsed entity, a CDATA section is a section of element content that is marked for the parser to interpret as only character data, not markup. A CDATA section is merely an alternative syntax for expressing character data; there is no semantic difference between character data that manifests as a CDATA section and character data that manifests as in the usual syntax in which "<", ">" and "&" would be represented by "<", “>” and "&", respectively.

Characters like "<" and "&" are illegal in XML elements.

"<" will generate an error because the parser interprets it as the start of a new element.

"&" will generate an error because the parser interprets it as the start of a character entity.

A CDATA section starts with "<![CDATA[" and ends with "]]>"

For example, instead of using the line “The last word of the line is >>> here <<&lt” the following line could be used:

<! [ CDATA [The last word of the line is >>> here <<<] ] >

All characters enclosed between these two sequences are interpreted as characters, not markup or entity references. For example, in a line like this:

<sender>John Smith</sender>

the opening and closing "sender" tags are interpreted as markup. However, if written like this:

<![CDATA[<sender>John Smith</sender>]]>

then the code is interpreted the same as if it had been written like this:

<sender>John Smith</sender>

That is, the "sender" tags will have exactly the same status as the "John Smith"— they will be treated as text.

Some text, like JavaScript code, contains a lot of "<" or "&" characters. To avoid errors script code can be defined as CDATA. Everything inside a CDATA section is ignored by the parser.

In the example above, everything inside the CDATA section is ignored by the parser.

Example:

Writing a tutorial about XML would contain:

"In XML you need elements which have a starting tag <song> and end tag </song>"

The markup for this sentence would be:

<div> In XML you need elements which have a starting tag <song> and end tag </song></div>

In order to avoid this inconvenience, XML has a method to treat markup as text (or CDATA). This is done by simply enclosing the text with markup that we want to be displayed (not interpreted) in a CDATA element.

"<!CDATA[In XML you need elements which have a starting tag <song> and end stag </song>]]>"

Between the start of the section, "<![CDATA[" and the end of the section, "]]>", all character data is passed directly to the application.

A CDATA section cannot contain the string "]]>". Nested CDATA sections are not allowed.

The "]]>" that marks the end of the CDATA section cannot contain spaces or line breaks.

Comments are not recognized in a CDATA section. If present, the literal text "" will be passed directly to the application. CDATA does not work in HTML.

All text in an XML document will be parsed by the parser. But text inside a CDATA section will be ignored by the parser.

5. Explain the various WSDL elements.

Ans.- WSDL is an XML grammar for describing web services. The specification is divided into six major elements:

Definitions:- The definitions element must be the root element of all WSDL documents. It defines the name of the web service, declares multiple namespaces used throughout the remainder of the document, and contains all the service elements.

Types:- The types element describes all the data types used between the client and server. WSDL is not tied exclusively to a specific typing system, but it uses the W3C XML Schema specification as its default choice. If the service uses only XML Schema built-in simple types, such as strings and integers, the types element is not required.

Message:- The message element describes a one-way message, whether it is a single message request or a single message response. It defines the name of the message and contains zero or more message part elements, which can refer to message parameters or message return values.

PortType:- The portType element combines multiple message elements to form a complete one way or round-trip operation. For example, a portType can combine one request and one response message into a single request/response operation, most commonly used in SOAP services.

Binding:- The binding element describes the concrete specifics of how the service will be implemented on the wire. WSDL includes built-in extensions for defining SOAP services, and SOAP-specific information therefore goes here.

Service:- The service element defines the address for invoking the specified service. Most commonly, this includes a URL for invoking the SOAP service. In addition to the six major elements, the WSDL specification also defines the following utility elements:

Documentation:- The documentation element is used to provide human-readable documentation and can be included inside any other WSDL element.

Import:- The import element is used to import other WSDL documents or XML Schemas. This enables more modular WSDL documents. For example, two WSDL documents can import the same basic elements and yet include their own service elements to make the same service available at two physical addresses. Note, however, that not all WSDL tools support the import functionality as of yet.

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B.Sc. IT BT0078 (Semester 3, Website Design) Assignment

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