Introduction There is more to computers and processors than simply PCs. In fact computers are ubiquitous in everyday life. This unit challenges how we view computers through the examples of processors in kitchen scales and digital cameras, as well as a work of art that, at heart, is a computer. This unit is from our archive and is an adapted extract from Computers and processors (T224) which is no longer taught by The Open University. If you want to study formally with us, you may wish to explore ot
6.2 Authority and the variety of information sources Technology has massively increased the number and variety of news sources that we have access to. We still have printed books, magazines and newspapers, while digital techniques have increased the number of broadcast radio and TV channels that we can get. On the Web we have access to online versions of many of these. This allows us access to media that previously would have been inaccessible. With traditional news sources such as these, we have some understanding of the authority that t
4.4.2 Battery parameters Now that we have covered some background on electricity, I will return to discussing batteries. What do you think would be the important characteristics of a battery for a portable ICT device such as a camcorder or a 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. This unit looks at the technologies used to acquire information about 4.3 Ethical and legal considerations You will need to be aware of privacy and confidentiality in relation to online communication. Email is generally considered private and should not be quoted without permission. Some conferences are not wholly public, so messages should not be copied outside the conference. Online discussion may be read by people from other cultures and backgrounds, so be careful to avoid giving offence. Although people are usually very tolerant, it is still possible that someone could sue for libel. 4.2.4 Make clear your perspective Try to avoid speaking impersonally: ‘This is the way it is…’, ‘It is a fact that…’. That will sound dogmatic and leaves no room for anyone else's perspective. Why not start, ‘I think…’? A common abbreviation is IMHO (in my humble opinion) – or even IMNSHO (in my not so humble opinion). If you are presenting someone else's views, say so, perhaps by a quote and acknowledgement. 2.2 Evaluating web resources One of the good things about the Web is also one of its drawbacks – anybody can publish anything. This means that the Web is an amasing source of information and is full of fascinating resources. However, in order to get to useful information you may have to work your way through lots of irrelevant material. Even when you think you have found something relevant, how do you know it is reliable, and how can you judge the quality, accuracy and bias of what you find? Most publicatio References 6.6 Modelling the relationships between use cases There are two situations when you would consider adding details to a use case diagram: to identify a common task (and its associated scenarios) that is shared between two or more use cases; to record any alternatives or additions to the main success scenario as separate use cases. In both situations, the new tasks are shown as new use cases (ovals) and, as you will see below, the UML provides a suitable notation (known as 6.4 Scenarios The purpose of a use case is to meet the goal of its associated actor(s), such as a guest making a reservation with a hotel. This implies that a use case should include everything that must be done to meet that goal. For example, if it is necessary to check the availability of rooms in the hotel for the desired length of stay before accepting a reservation, then we expect the use case to contain that check. In general, a use case contains a narrative about the flow of events that specifies a 7.2.1 E-shop This is the most ubiquitous form of commerce on the World Wide Web. It involves a company presenting a catalogue of its wares to internet users and providing facilities whereby such customers can purchase these products. Almost invariably such a site will contain facilities for ordering and paying for products by means of credit cards. The sophistication of sites described by this business model range from just the simple presentation of a static catalogue to the presentation of an interactiv 6.4 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. 6.3 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 6.1 The architecture of a typical e-commerce system Before finishing this unit 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. 5.6 Design Designing a distributed system can also be a problem, for example the fact that computers in a distributed system are joined by communication media which can stretch over thousands of miles provides an added dimension to the design process in that response time can be a problem. Another, equally serious problem is that of reliability, for example the fact that a hardware malfunction can bring down a poorly-designed distributed system. As an example of one design problem that a distribut 5.5 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 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 4.1 Legacy technology The aim of Section 5 is to examine some of the issues and problems which affect the devekopment of Internet, e-commerce and e-business applications. The World Wide Web was developed as a way of dispensing documentation within the large research laboratory at CERN in Geneva. I am sure that the originator of the technology, Tim Berners-Lee, did not realise at that stage how it would expand and become a major component of our economic infrastructure. Because many of the developers o 3.4 Newsgroups A newsgroup is a collection of internet users who are interested in a particular topic. The topic may be a technical one, for example the LINUX operating system, or a recreational one such as fly fishing. Members of a newsgroup send messages associated with a particular issue such as the date of release of the next version of LINUX or the efficacy of using certain fiies on certain rivers. Each message – known as a posting – will contain the user's thoughts on the topic. Once 1.6.3 Supporting users and user processes Use of a database involves user processes (either application programs or database tools) which must be developed outside of the database development. In terms of the three-schema architecture we now need to address the development of the external schema. This will define the data accessible to each user process or group of user processes. In reality, most DBMSs, and SQL itself, do not have many facilities to support the explicit definition of the external schema. However, by using built-in q
Activity 19
