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2.2.2 Drawing the boundary

Deciding where to place the system boundary is an important consideration in that we have to think about what to include and exclude. This isn't always an easy decision to make and it often depends on the perspective of the person viewing the system.

The system maps in Figures 1
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2.2 A system map

One way of explaining and analysing a system is to represent it in a graphical form, known as a system map. I'll use the example of a system for making an appointment with a doctor in a health centre to illustrate this point. In this example, the health centre uses a computerised booking system and the patient may phone or visit the health centre to make an appointment. Therefore, the system includes a patient, a receptionist, a doctor, and a computerised booking system. The example sh
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Introduction

This unit is from our archive and it is an adapted extract from Networked living: exploring information and communication technologies (T175) which is no longer in presentation. If you wish to study formally at The Open University, you may wish to explore the courses we offer in this curriculum area.

Many governments across the world are moving towards the use of infor
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References

Eyewitness Travel Guide (1997) Amsterdam. London, Dorling Kindersley. pp. 120-1.
Götz, V. (1998) Color and Type for the Screen. Berlin, RotoVision (in collaboration with Grey Press).
Hartley, J. (1994) Designing Instructional Text. 3rd edn. London, Kogan Page.
Michaelis, P. R. and Wiggins, R. H. (1982) ‘A human
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1.6.5 Using speech to good effect

Speech output is a powerful way of communicating information. It has particular benefits for the visually impaired. For those whose eyesight is good, speaking lifts may seem a novelty, but they provide useful information and reassurance for the visually impaired. Some applications of the technology have less obvious benefits, such as supermarket checkouts that read out the product and prices. These were found to breach the customer's sense of privacy and to be noisy. Again, good design depend
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7.5 Active and passive tags

Activity 30: exploratory

Read the extracts below. Using the information they contain, make notes about the main differences between active and passive RFID tags. You will get more out of this exercise if you make a serious attempt to d
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3.1 Introduction

This section starts by broadly classifying different types of network, first by the nature of the communication links used to connect devices and then by a network's geographical spread. It then examines in more detail a network which uses a cabled communication link.

A networked device is often referred to as a node so we shall use this term in the sections that follow. A node is any device (for example, computer, printer, server) connected to a network, either as an end point (
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2.8 Attenuation and distortion

As a signal travels from one device to another it has two problems to overcome. The first is that it gets weaker the further it travels, because some of its energy is absorbed by the transmission medium. This effect is known as attenuation. The extent of attenuation depends on the distance it has to travel and on the type of medium it is travelling through. An amplifier can be used to boost the signal power at the transmitter and receiver, and if necessary at various points in the tran
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4 The eBay phenomenon – what it means

Writers on e-business group Internet processes into four categories, using this grid:

Figure 13
Figure
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6.7 Stereotypes

In the UML, a stereotype is a way of adding detail to any part (element) of a model. It is a way of expressing variation or a usage distinction that tells you more about the original element. For example, the line drawn between an actor and a use case indicates that there is an association between them. We could add the stereotype «communication» to such a line to emphasise the communication that takes place between the two. In practice, this stereotype is left out because it is the
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2.7 Other commercial websites

So far I have detailed e-commerce applications which are connected with very large organisations; to conclude this section it is worth looking at a number of smaller applications, many of which are distinguished by the fact that they are novel. They are in contrast to the applications discussed in previous subsections which mainly consist of standard functions such as order processing.

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1.7 Testing

The aim of testing is to uncover errors in the design and implementation of the database, its structure, constraints and associated user and management support. Testing is usually considered to involve two main tasks – validation and verification. Without adequate testing users will have little confidence in their data processing.

Validation answers the question: has the right database been developed to meet the requirements? It attempts to confirm that the right database has been co
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Acknowledgements

Grateful acknowledgement is made to the following sources for permission to reproduce material within this product.

Figure 1 The National Gallery, London;

Figure 3 NOAA-AVHRR image provided courtesy of the Canada Centre for Remote Sensing, Natural Resources Canada;

Figure 4(a) Map extract produced by FWT and reproduced with the kind permission of the Association of Train Operating Companies;

Figure 4(b) Reproduced from multimap.com. Ordnance Survey map with permission
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5.2 Art and the common computer

Art is difficult to define. But all art involves the Exercise of human skill. A natural object, such as a piece of driftwood, a flower, a bird song, can move us to admire it as beautiful or intriguing or comforting, but it isn't art. Artists (be they photographers, painters, sculptors, actors, musicians, authors or dancers) use their skill to transform natural objects, materials or signs (paint, clay, their own body or voice, the sounds of musical instrument, words) into somethi
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5.1.2 The human genome

All life is ‘encoded’ chemically in genes. What this means is that the structure of an organism, the organs it possesses, its colouring, and so on are all determined by different genes. A very simple organism may have just a few genes, and a complex one tens of thousands. The ‘map’ of an organism's genes is referred to as its genome. It shows, in essence, which genes give rise to which characteristics or traits of the organism. The word ‘template’ would describe the
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4.1 Where am I and how do I get to … ?

Computers can be used to find things and the obvious thing they can find is information. The World Wide Web (WWW or just the web) is just one example of a vast store of information which can be searched to find what you want using computers (The web consists of linked data which is accessed via the internet using a browser). But computers can also ‘find’ things in the sense of locating them geographically, either by generating maps that can be used for navigation or by locat
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1.1 What this unit is about

Each venture

Is a new beginning, a raid on the inarticulate …

T. S. Eliot, ‘East Coker’

Some years ago I was playing with my nephew. ‘Guess what’, he said. ‘My gran remembers before there was television!’ He was clearly thinking about the past in terms of ‘before there was television’.

At that time, I was working in computing, and most people couldn't really un
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Learning outcomes

After studying this unit you should be able to:

  • identify some of the instances in daily life where a computer is, or is likely to be, involved;

  • given a simple scenario, list most of the obvious information or data required by the parties in that scenario, and give some examples of how the information or data might be used;

  • explain briefly what perceptual data is, and how it is turned into a form that can be used by a person for reasoning or by a co
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3.11.3 Maths, sciences and technology

The additional points we would want you to be aware of as you plan your revision in these subjects relate to the different ways in which you are called upon to present your answers. These might be:

  • short reports

  • multiple-choice answers

  • dif
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5.1.6 Are the conclusions justified?

Though I was interested in the idea of treating high incomes as ‘pollution’, I did wonder whether taxing people to pay for the pollution caused by their rising incomes would work. In general though I was reasonably convinced by the conclusions Layard drew. On the other hand, if I was studying the subject more seriously, I might find that wider reading and further thought would make some of the conclusions seem less convincing.


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