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User interface language: English | Español

Date	May 2018	Marks available	3	Reference code	18M.2.SL.TZ0.9
Level	SL	Paper	2	Time zone	no time zone
Command term	Outline	Question number	9	Adapted from	N/A

Question

A web application (app) runs on mobile devices such as smartphones and tablets. It allows users to locate their position in real time on a map, as they walk around a city, as well as the surrounding attractions. The app uses icons to represent tourist attractions such as art galleries and museums. When the user clicks on the icon, further details are shown, such as opening times. The app includes some use of client-side scripting.

Many art galleries have websites that can be found by search engines. White hat techniques and practices allow website developers to optimize the search process. It is good practice to maintain the source code of websites up-to-date with actual information.

Outline the functioning of this app. Include specific references to the technology and software involved.

[3]

a.i.

With reference to the use on mobile devices, outline a feature of this application that may rely on client-side scripting.

[2]

a.ii.

State two metrics used by search engines.

[2]

b.i.

Explain why maintaining a clean HTML source code of a website by removing old information optimizes the search process.

[5]

b.ii.

The evolution of the web, architectures, protocols and their uses has led to increasingly sophisticated services that run on peer-2-peer (P2P) architectures.

Explain how a P2P network can provide more reliability than a client-server model.

[4]

Markscheme

Award up to [3 max].

Award [1] for showing understanding of the need of each of the following: GPS, mapping software, underlying distributed information.

The GPS of the device gives its current location (coordinates);

Coordinates sent out through the Internet (with 3G/4G/5G/Wifi/using the specific features of the mobile device OS);

Coordinates are linked to map software (e.g. Googlemaps) to retrieve current’s device position and neighbourhood information (using thematic databases);

And integrated with further annotations (relative to museums) that can be provided by third-party services;
OR by information incrementally gathered from users;
OR by further databases (GIS services);
OR by interrogating an (incremental) database accessible from the server where the app has been downloaded from, for its first installation;

a.i.

Award up to [2 max].

Award [1] for identifying a feature and award [1] for reasonable expansion of the feature up to [2 max].

Example 1:
The design of the front-end (the user interface) with the specific mobile device;
So that the commands are specific (and built-in) within the device, to support interactive use;
(With the effect that the app can be used across a range of devices and mobile operating systems;)

Example 2:
To personalize the app with a “history” on the client’s side, after the first use of the application;
So that only the new information added in the database (underlying sources used by the app) can be fetched by the client’s script;

a.ii.

Award up to [2 max].
Number of hits;
Popularity of linking pages;
Amount of links to the same page departing from the source page;
Trustworthiness of the linking domain;
Relevance of content between source and target page;
Time to download;
…(there are others).

b.i.

Award up to [5 max].
Old information is more likely to be retrieved by web crawlers;
But this requires time to crawl;
But this interferes with the response time for the current search;
And it may even be penalised by policies in search engines;
Without returning currently relevant information;
Example of old information are old or broken links/orphan pages/old text masked by comments in the HTML code, and it can be revised from time to time;
Cleanly written code allows for a more efficient search process;
Which facilitates correct indexing;

Note: Award [2 max] for a generic response.

b.ii.

Award up to [4 max].
In P2P all machines can interchangeably be client as well as server (no division of client-server);
Data and services can be replicated across sites, and be retrieved from them;
Services are virtualized/reside on virtual machines;

Therefore, if one node is unavailable the service can still be provided by resorting to other nodes;
OR
System updates can be made while not interrupting the provision of the service
OR
The failure of a node does not imply the failure of the entire network

Examiners report

[N/A]

a.i.

[N/A]

a.ii.

[N/A]

b.i.

[N/A]

b.ii.

[N/A]

Syllabus sections

Option C: Web science » C.1 Creating the web

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17N.2.SL.TZ0.8d:

A fragment of a script and a web form are provided below.
In the script some functions are not implemented, and only their specification is provided.

<?php
  //include a database of urls
  include('url_db.php');
  $url = $short = "";

  if ($_SERVER["REQUEST_METHOD"] == "POST")
  { $url = $_POST['url'];
    $short = make_short($url);
    function make_short($u)
    { $x = make_alpha_string($u);
      $y = first4_last4($x);
      $z = limits($x);
      $v = $y. ".".$z;   //string concatenation
      return $v;
  }

  function make_alpha_string($u)
  { // It removes, in this order: substrings corresponding to
    // protocol names, the substring www, and all characters
    // except for letters
  }

  function first4_last4($u)
  { // It returns the string made of the first 4 characters
    // followed by the last 4 characters of $u
  }

  function limits($u)
  { // It returns the string made of the first character and
    // last character of $u
  }

  mysql_query("
    INSERT INTO url_db(orig_url, short_url, url_ip) VALUES
    ( '".$_POST['url']."',
      '".$short."',
      '".$_SERVER['REMOTE_ADDR']."'
    )
  ");
 }
?>

<form method="post" action="">
URL:
<input type="text" name="url" />
<br><br>
<input type="submit" name="Submit" value="Submit" />
</form>

Describe the processing that occurs when the form is filled with the URL https://www.the2nd.org/bin.php?id=70 that the server discovers is associated with the IP address 172.16.254.1.

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Option C: Web science

Question

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