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Amazon SimpleDB is another service from Amazon that uses its Dynamo technology. With SimpleDB, Amazon has at last incorporated database as part of the company's web services. SimpleDB is currently available to the public as a beta service, with several technical limitations, including:
A single query will timeout after 5 seconds.
Only strings are available as data type.
Data query, write, retrieval are type casted into strings.
Strings cannot have more than 1,024 characters.
An item can have a maximum of 256 attributes.
In open beta testing, a SimpleDB domain is capped at 10GB capacity.

SimpleDB is not RDBMS (relational database management system), but it rather operates in a far simpler fashion. Amazon SimpleDB's data are stored as Domain → PKeys, PKeys → Attributes, and within each attribute, Key → Value. For instance:

Key:1
Attributes:
Category: Company
Name: Cellopoint
Website: http://www.cellopoint.com

Being a database, SimpleDB comes with its own querying API.

Installing the PHP Library for Amazon SimpleDB:
1. Download PHP Library for Amazon SimpleDB at Amazon Web Services (AWS) website.
2. Extract the file.
3. Request and retrieve Access Key ID and Secret Access Key from AWS.

Client connection testing:
1. cd to PHP Library for Amazon SimpleDB directory.
2. vim test_client.php
<?php
$AWS_ACCESS_KEY_ID = …
$AWS_SECRET_ACCESS_KEY = …

require_once('Amazon/SimpleDB/Mock.php');
$service = new Amazon_SimpleDB_Mock();

require_once('Amazon/SimpleDB/Client.php');
$service = new Amazon_SimpleDB_Client($AWS_ACCESS_KEY_ID, $AWS_SECRET_ACCESS_KEY);
?>
3. Run test_client.php

Inserting data:
1. PHP aplication
$domain= “MyDomain”;
$item = “Product01”;

$attr1 = new Amazon_SimpleDB_Model_ReplaceableAttribute();
$attr1->withName('Category')->withValue('Device');

$attr2 = new Amazon_SimpleDB_Model_ReplaceableAttribute();
$attr2->withName('Name')->withValue('D01');

$attrArr = array($attr1, $attr2);

$request = new Amazon_SimpleDB_Model_PutAttributesRequest();
$request->withDomainName($domain)->withItemName($item)->setAttribute($attrArr);

invokePutAttributes($service, $request);
2. Service response

Service Response
==============================
PutAttributesResponse
ResponseMetadata
RequestId
...
BoxUsage
…

Retrieving data:
1. PHP application
$request = new Amazon_SimpleDB_Model_QueryRequest();
$request->setDomainName('MyDomain');
$request->setQueryExpression(“['Category' = 'Device']”);

invokeQuery($service, $request);
2. Service response
GetAttributesResponse
GetAttributesResult
Attribute
Name
Category
Value
Device
…
ResponseMetadata
RequestId
…
BoxUsage
..

Google client products are capable of updating themselves to a newer version without end-user intervention. This is known as “auto-updating.”

Most of Google client products possess the auto-update feature, but with different implementation. Some has their own auto-update solutions, while others utilize the common auto-updater code and the common auto-updater server.

Google sought for client products to minimize code duplication and avoid maintaining multiple servers that essentially perform identical functionality. As result they considered unifying all client products under a single auto-update solution. This decision was influenced by the fact the evolution of Microsoft Windows, which made this unification almost mandatory. Window Vista has a strict security model that restricts the ability of most applications on a machine to perform system-changing activities, including: modifying the Windows registry, writing to the Program Files directory, and in some cases writing any persistent change to the system at all. The update of an installed program requires all these modifications, which would lead traditional auto-updating to fail on Microsoft Vista.

The lack of shared code brought another issue: each auto-update implementation had its own subset of desired features. Many of them failed to have multiple update tracks, or define a consistent versioning mechanism. Code unification allowed Google to deploy a rich set of auto-update capabilities to all its client applications.

As the number of Google applications increased, the improvement of the overall install user experience became increasingly desirable. Traditionally, the browser would prompt the end-user with a series of technical and confusing dialogs which encouraged the user to abandon their installation. Then the user was led to a wizard filled with choices that they did not need to know or know how to decide amongst. These result in a bad user experience during the product installation process.

In order to meet all the requirements and challenges mentioned above, Google developed a shared client infrastructure that handles all installation and auto-updating tasks for Google Windows client products. This client communicated with a single Google auto-update server. This server, together with the client, is named Google Update. And the project is known as Omaha.

jQTouch is a jQuery plugin with native animations, automatic navigation, and themes for mobile WebKit browsers such as iPhone, Nexus One, and Palm Pre. jQuery is a fast and concise JavaScript library that simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development. The combination of jQuery and jQTouch allows any web application developer with little experience in jQuery to build mobile applications.

As an example, consider a simple home panel. This is the HTML for Home panel:

<html>
<head>
<title>To-Do</title>
<link type=”text/css” rel=”stylesheet” media=”screen” href=”jqtouch/jqtouch.css”>
<link type=”text/css” rel=”stylesheet” media=”screen” href=”themes/jqt/theme.css”>
<script type=”text/javascript” src=”jqtouch/jquery.js”></script>
<script type=”text/javascript” src=”jqtouch/jqtouch.js”></script>
<script type=”text/javascript”>
var jQT = $.jQTouch({
icon: ‘todo.png’,
statusBar: ‘black’
});
</script>
</head>
<body>
<div id=”home”>
<div class=”toolbar”>
<h1>To-do</h1>
</div>
<ul class=”edgetoedge”>
<li class=”arrow”><a href=”#about”>About To-Do</a></li>
</ul>
</div>
<div id=”about”>
<div class=”toolbar”>
<h1>About To-Do</h1>
<a class=”back” href=”#”>Back</a>
</div>
</div>
</body>
</html>

The HTML is simple, its body composed of two divs as children. The integration with jQuery and jQTouch is in the HTML head. An analysis of the HTML document head:

• jqtouch.css is a required file, defining structural design rules specific to mobile devices, including animation handling, and orientation.
• theme.css is a CSS theme included with jQTouch.
• jquery.js is the core file of jQuery framework. jQTouch requires jQuery, and it comes with its own copy of jQuery.
• jqtouch.js is the core file of jQTouch.
• variable jQT is the jQTouch initiated object. Two properties are defined in the Home panel: icon and statusBar.

jQTouch has several properties that allow users to customize the behavior and look of their apps. In this case, icon indicated the custom Web Clip icon, and statusBar controls the color of the strip at the top of the app in full screen mode.

All in all, jQTouch is a framework that facilitates developers to add native-looking animations to a web app.