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5.4 Structure and data

A problem that is being increasingly experienced by internet companies is the fact that they have to interchange a large amount of data and that such data inherently lacks structure. For example, HTML has proved to be an enduring markup language for developing web pages; however, there are no facilities within the language, for example, to indicate whether an item of data, say a three-digit number, represents the price of a commodity or some hourly rate charged by a company employee.

Th
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5.2 Programming and abstraction

In the early 1990s programming an application for the internet was a tough proposition. I remember that I once had an application which required a very simple form of communication with another application located at a remote computer. I used a technology known as Winsocks which required me to carry out some pretty arcane code development just to send a simple test message to another computer and to receive a reply from that computer.

Java, when it appeared in 1996, enabled developers t
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5.1 Security and privacy

The internet is not a particularly secure place. There are two aspects to this: the first is that information is widely published throughout the internet which can be used for criminal and near-criminal activities. The second aspect is that since the internet is an open system, details of its underlying technologies are freely available to anybody. This means that the way data passes through the internet is in the public domain; the consequence of this is that, theoretically, anyone with the
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6.1 What is a business model?

The aim of this section is to look at some of the business models which have been used to drive internet applications. A business model is a high-level description of an application type which contains all the common features which can be found in specific examples of the model. For example, one of the most popular business models is the e-shop which describes a website that sells products. The model is general in that it does not describe the item that is sold or the mechanisms that a
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5.4 The Sydney Olympic Games system

IBM was responsible for the computer systems which were used in the 2000 Olympic Games. There were a number of components to the system, these included:

  • A website which was publicly accessible and which contained features on the Games, the competitors and the results.

  • A Games management system which administered the logistics of the Games, for example arranging transportation, accreditation and accommodation for athletes.


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5.3 The architecture

The architecture of the system is shown in Figure 4. It consists of a number of components. The most important of these is the web server. This communicates with browsers used by customers.

There are two other computers that are used in the system which are directly connected to the web server: a mail server which sends and receives mail from customers and a mailing list server which administers the mailing lists of customers and their interests. Both these servers communicate with the
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5.2 The application

The first application I shall describe is that of an online bookseller. Such a book sales system would carry out a number of functions:

  • It would allow the user to browse through a catalogue of books.

  • It would allow the user to browse through a list of the most popular books, with the list being updated every hour.

  • It would provide the facility whereby a user can buy books and add them to a notional shopping basket.


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5.1 The architecture of a typical e-commerce system

Before finishing this course it is worth looking at the architecture of a typical e-commerce system in order to see some of the technologies. This is followed by details of a real application which I shall use to discuss some of the issues involved in distributed system development. The description used is closely modelled on the Amazon site.


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4.6 Problems with transactions

A distributed transaction is a sequence of operations applied to a number of distributed databases which form a single functional step. For example, a transaction which moves an amount of money from a customer's account to an account owned by the same customer is an example of a transaction. It consists of two operations: the operation of debiting one account and the operation of crediting another account. There are a number of problems associated with distributed transactions. This section w
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2.7.5 Email providers

These are sites which provide free email facilities; often they provide other facilities such as sending anonymous mail and constructing mailing lists. Such sites are valuable to users who are too impecunious to be able to afford conventional mailing software and to frequent travellers who can access such sites anywhere in the world. Their main disadvantage is that they tend to be slow compared with conventional mailing utilities such as Microsoft Outlook and Eudora.


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2.7.4 Change notification sites

These sites are a variation on link checking sites. Here, the customer is notified not when a web document becomes unavailable, but when the document is changed. For example, the customer might be interested in a particular page which advertises some holiday package offers to a particular destination and wants to keep abreast of any changes to the page which might signal the fact that a new improved offer has been added.


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2.7.3 Archive sites

These are websites which offer customers a facility for storing their files at a safe location. This guards against anything disastrous happening to the customer's computer and their losing valuable data. Often the files will be duplicated at a number of computers at different locations in order to guard against the possibility of one of the locations being affected by a natural disaster such as an earthquake, or a computer being affected by a catastrophic failure which results in its stored
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3.5.1 Anonymous remailers

An anonymous remailer is a website which enables you to send an email anonymously to some recipient. The main reason for this is to do with something known as spam. This term describes unsolicited email which tries to sell the recipient something.

Spam

Throughout the internet you can
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4.5 Structure and data

A problem that is being increasingly experienced by internet companies is the fact that they have to interchange a large amount of data and that such data inherently lacks structure. For example, HTML has proved to be an enduring markup language for developing web pages; however, there are no facilities within the language, for example, to indicate whether an item of data, say a three-digit number, represents the price of a commodity or some hourly rate charged by a company employee.

Th
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4.4 The speed of development

E-commerce consultants speak of a web year. This is the time which it takes to bring to implementation a conventional system that would normally take a calendar year to develop. Current estimates are that one calendar year is equivalent to seven web years. Nowhere is there more of an imperative for companies to develop products and services quickly, together with the computing infrastructure required to support them, than in e-commerce. In software engineering terms this has given rise to a n
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4.3 Programming and abstraction

In the early 1990s programming an application for the internet was a tough proposition. I remember that I once had an application which required a very simple form of communication with another application located at a remote computer. I used a technology known as Winsocks which required me to carry out some pretty arcane code development just to send a simple test message to another computer and to receive a reply from that computer.

Java, when it appeared in 1996, enabled developers t
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Learning outcomes

After studying this course, you should be able to:

  • detail what is meant by the term ‘e-commerce’

  • examine some typical distributed applications

  • detail some of the problems that are encountered when developing distributed applications

  • describe briefly some of the technologies that are used to support distributed applications

  • show how some of the technologies detailed in the course are used in concert to realise a typi
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Introduction

This unit examines the type of system which is described by the umbrella term ‘e-commerce’. A number of typical application areas are examined including retailing using the internet, supply chain management and online auctions. The unit also looks at some of the underlying technologies used to implement e-commerce applications, for example web technology. The final part of the unit looks at some of the problems which are encountered when developing distributed e-commerce systems, for exam
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Conclusion

Relational database systems underpin the majority of the managed data storage in computer systems. In this course we have considered database development as an instance of the waterfall model of the software development life cycle. We have seen that the same activities are required to develop and maintain databases that meet user requirements.


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1.8 Maintenance

Databases are one of the more enduring software engineering artefacts; it is not uncommon to find database implementations whose use can be traced back for 15 years or more. Consequently, maintenance of the database is a key issue.

Maintenance can take three main forms:

  • Operational maintenance, where the performance of the database is monitored. If it falls below some acceptable standard, then reorganisation of the database, usuall
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