A description  of the ACID properties of a transaction

According to Guilfoyle Warner (1994),” When a transaction processing system creates a transaction, it will ensure that the transaction will have certain characteristics. The developers of the components that comprise the transaction are assured that these characteristics are in place. They do not need to manage these characteristics themselves. These characteristics are known as the ACID properties. ACID is an acronym for atomicity, consistency, isolation, and durability.

Atomicity

The atomicity property identifies that the transaction is atomic. An atomic transaction is either fully completed, or is not begun at all. Any updates that a transaction might affect on a system are completed in their entirety. If for any reason an error occurs and the transaction is unable to complete all of its steps, the then system is returned to the state it was in before the transaction was started. An example of an atomic transaction is an account transfer transaction. The money is removed from account A then placed into account B. If the system fails after removing the money from account A, then the transaction processing system will put the money back into account A, thus returning the system to its original state. This is known as a rollback, as we said at the beginning of this chapter..

Consistency

A transaction enforces consistency in the system state by ensuring that at the end of any transaction the system is in a valid state. If the transaction completes successfully, then all changes to the system will have been properly made, and the system will be in a valid state. If any error occurs in a transaction, then any changes already made will be automatically rolled back. This will return the system to its state before the transaction was started. Since the system was in a consistent state when the transaction was started, it will once again be in a consistent state.

Looking again at the account transfer system, the system is consistent if the total of all accounts is constant. If an error occurs and the money is removed from account A and not added to account B, then the total in all accounts would have changed. The system would no longer be consistent. By rolling back the removal from account A, the total will again be what it should be, and the system back in a consistent state.

Isolation

When a transaction runs in isolation, it appears to be the only action that the system is carrying out at one time. If there are two transactions that are both performing the same function and are running at the same time, transaction isolation will ensure that each transaction thinks it has exclusive use of the system. This is important in that as the transaction is being executed, the state of the system may not be consistent. The transaction ensures that the system remains consistent after the transaction ends, but during an individual transaction, this may not be the case. If a transaction was not running in isolation, it could access data from the system that may not be consistent. By providing transaction isolation, this is prevented from happening.

Durability

A transaction is durable in that once it has been successfully completed, all of the changes it made to the system are permanent. There are safeguards that will prevent the loss of information, even in the case of system failure. By logging the steps that the transaction performs, the state of the system can be recreated even if the hardware itself has failed. The concept of durability allows the developer to know that a completed transaction is a permanent part of the system, regardless of what happens to the system later on.

Describe a TP monitor environment.

TeleProcessing monitor or Transaction Processing monitor) A control program that manages the transfer of data between multiple local and remote terminals and the application programs that serve them. It may also include programs that format the terminal screens and validate the data entered.

In a distributed client/server environment, a TP monitor provides integrity by ensuring that transactions do not get lost or damaged. It may be placed in a separate machine and used to balance the load between clients and various application servers and database servers. It is also used to create a high availability system by switching a failed transaction to another machine. A TP monitor guarantees that all databases are updated from a single transaction

Examples of popular TP monitors are CICS, a veteran TP monitor used on IBM mainframes and the Unix-based Tuxedo and Encina products.”

Reference:

C. Guilfoyle and E. Warner (1994) “Intelligent Agents: The New Revolution in Software” Ovum

1. Describe what software agents are.

Software agents are probably the fastest growing area of Information Technology (IT). They are being used, and touted, for applications as diverse as personalised information management, electronic commerce, interface design, computer games, and management of complex commercial and industrial processes. Despite this proliferation, there is, as yet, no commonly agreed upon definition of exactly what an agent is — Smith et al. (1994) define it as “a persistent software entity dedicated to a specific purpose”; Selker (1994) takes agents to be “computer programs that simulate a human relationship by doing something that another person could do for you”; and Janca (1995) defines an agent as “asoftware entity to which tasks can be delegated”. To capture this variety, a relatively loose notion of an agent as a self-contained program capable of controlling its own decision making and acting, based on its perception of its environment, in pursuit of one or more objectives will be used here. Within the extant applications, three distinct classes of agent can be identified. At the simplest level, there are “gopher” agents, which execute straightforward tasks based on pre-specified rules and assumptions (eg inform me when the share price deviates by 10% from its mean position or tell me when I need to reorder stock items). The next level of sophistication involves “service performing” agents, which execute a well defined task at the request of a user (eg find me the cheapest flight to Paris or arrange a meeting with the managing director some day next week). Finally, there are “predictive” agents, which volunteer information or services to a user, without being explicitly asked, whenever it is deemed appropriate (eg an agent may monitor newsgroups on the INTERNET and return discussions that it believes to be of interest to the user or a holiday agent may inform its user that a travel firm is offering large discounts on holidays to South Africa knowing that the user is interested in safaris).

Reference:J. L. Alty, D. Griffiths, N. R. Jennings, E. H. Mamdani, A. Struthers, and M. E. Wiegand (1994)
“ADEPT – Advanced Decision Environment for Process Tasks: Overview & Architecture” Proc.
BCS Expert Systems 94 Conference (Applications Track), Cambridge, UK, 359-371.

C. Guilfoyle and E. Warner (1994) “Intelligent Agents: The New Revolution in Software” Ovum
Report.

http://www.csc.liv.ac.uk/~mjw/pubs/iee-review96.pdf

What is meant by a location based service?

A location-based service (LBS) is an information and entertainment service, accessible with mobile devices through the mobile network and utilizing the ability to make use of the geographical position of the mobile device.

LBS services can be used in a variety of contexts, such as health, work, personal life, etc.  LBS services include services to identify a location of a person or object, such as discovering the nearest banking cash machine or the whereabouts of a friend or employee. LBS services include parcel tracking and vehicle tracking services. LBS can include mobile commerce when taking the form of coupons or advertising directed at customers based on their current location. They include personalized weather services and even location-based games. They are an example of telecommunication convergence.

This concept of location based systems is not compliant with the standardized concept of real time locating systems and related local services (RTLS), as noted in ISO/IEC 19762-5  and ISO/IEC 24730-1.

References:“Foundations of Location Based Services”, Stefan Steiniger, Moritz Neun and Alistair Edwardes, University of Zurich

“Permanent Reference Document SE.23: Location Based Services“

The difference between WAP and SMS services

This diagram illustrates the essential elements of WAP push . There are several ways that messages can be sent to mobile terminals: via PPG using PAP, via a provided access point to the SMSC using a protocol such as SMPP, or via the SMS-enabled terminal using the Mobile Application Part. In WAP push terminology, the sender of the message is called the push initiator.

In terms of the infrastructure provided, the mechanism used by the sender may cause the message to be routed to an SMSC or a push proxy for onward delivery. The PPG is capable of communicating directly to the recipient or using SMS as a delivery mechanism (either as plain text or as WAP push content). The recipient is either a push-capable terminal or a terminal with short messaging capability.

A major advantage of WAP push is the ability for the developer to send “active” content. In other words, depending on the type of content being sent and the application being addressed in the mobile terminal, the content will be presented to the recipient and can be automatically viewed. Even more powerful, the user may “take action” by using a developer-defined soft-key to immediately activate an application to accomplish a specific task, such as downloading a picture, making a purchase, or responding to a marketing offer. Indeed, WAP push may also be used to initiate activity without user intervention.

The Push system provides a superior level of service and features that build upon the experience of SMS. It provides for active content that can be used, in its simplest form, as a novel way of introducing new services, and in its more sophisticated form, to deliver the service itself. Push via the Openwave Push Proxy Gateway provides all the capabilities necessary to communicate to the widest possible group of users, while facilitating the development of applications by providing a single, open-standard push access point.

Reference:http://developer.openwave.com/docs/wappush_vs_sms.pdf

Scrapbooking is a hobby that has been growing in popularity. The underlying goal is to preserve memories in a unique and creative way. A scrapbooker starts with a scrapbook and a set of memories that they want to preserve for the future

A growing and maturing online shopper base. Roughly 5 million new U.S. households will shop online each of the next five years, creating a total of 63 million U.S. online shopping households in 2008. And as a growing percentage of these households use broadband, they’ll research more products and shop online more than their dial-up counterparts. Experienced shoppers will also continue to diversify their online purchasing, keeping sales on a steady climb: For the next five years, food and beverage, sporting goods, and home products will grow the fastest, outpacing more mature categories like books and travel.

First assessment elevator pitch.—Audio

<?php

$subject = “ITC382″;

switch ($subject) {
 
 case “ITC254″:
 echo “I am in ITC254 class”;
 break;
 case “ITC382″:
 echo “I am in ITC382 class”;
 break;
 default:
 print “I must have gotten lost again, I am suppose to be in $subject”;
 break;
}
?>

<?php
$lecturers = array(“Yann”, “Sam”, “Ven Yu”, “Tony”, “Anitha”);
echo $lecturers[1] ; // This will print Sams name
?>

<?php
// Adding two numbers together

$num1 = 88;
$num2 = 100;

echo “The first number is”, $num1;
echo “The second number is “,  $num2 ;

echo ” The total is “, $num1 + $num2;

?>