Web guide
Frightened of the internet? This free course, Web guide, will help you make effective use of the internet, giving you the basic skills required for using web-based resources. Useful tricks and tips are provided as well as information on web browsers, the main features of a browser window, how to look at websites, using hyperlinks, searching for information on the internet, copying text, avoiding computer viruses, and using PDFs.Author(s):
Systems thinking and practice
What is systems thinking and practice? The essence of systems thinking and practice is in 'seeing' the world in a particular way, because how you 'see' things affects the way you approach situations or undertake specific tasks. This free course will help you to learn about the problems of defining a system and meet some of the key concepts used in systems theory: boundary, environment, positive and negative feedback, etc.
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Acknowledgements Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Licence Course image: Author(s):
Conclusion This free course provided an introduction to studying Computing and ICT. It took you through a series of exercises designed to develop your approach to study and learning at a distance and helped to improve your confidence as an independent learner.Â
9.1 What is a state machine? An event is an occurrence of a phenomenon at a certain moment in time. The occurrence of the event itself is assumed to have no duration. Typically, when an event occurs, it affects the state of an object. A state machine is a model of the behaviour of a single object over time and helps you to understand how that object's state affects its reactions to events. Figure 18 shows a state machine diagram (known as a statechart diagram in the UML) relating to the occupancy of a room in a hot
8.2 Example of a university registration data model Here is a statement of the data requirements for a product to support the registration of and provide help to students of a fictitious e-learning university. A UK-based e-learning university needs to keep details of its students and staff, the courses that it offers and the performance of the students who study its courses. The university is administered in four geographical regions (England, Scotland, Wales and Northern Ireland). Information about each student should be initially
8.1 Introduction One type of data model is an entity–relationship data model. Experience has shown that data can be best described by relationships between entities. An entity is anything of interest about which data is recorded, such as roads, weather stations, trucks and weather station readings in the IceBreaker project in the book MRP. In general, there will be many relationships (or associations) linking the entities. A trivial example is the fact that a given weather reading
7.2 Exercises Draw an activity diagram for the main success scenario for the check out guest use case. 6.13 Exercises Write down a textual description (using the format of Table 2, reproduced below) of the use case check in guest, shown in Figure 3, also below. As part of your deliberations, identify any exceptions t 6.11 Issues with use cases There can be a tendency to make diagrams too complex. You can reduce the complexity of your use case diagram by: redrawing it at a higher level of abstraction; splitting it up into smaller modules, which the UML calls packages. In the case of the hotel chain, we might partition our model into the following three packages: reservations; checking guests in and o 6.10 To extend or include? Whatever kind of system you intend to develop, you will need to consider its security. Usually, we allow only trustworthy people to use a new system. Therefore, in a software solution we can envisage a log-on use case, which describes how a user gains access through some authentication procedure. How should such a requirement be included in the example of the hotel chain? By analogy with natural languages, the UML allows a number of ‘grammatically correct’ options each of which will 6.5 More about actors In the hotel example, you saw two actors in the use case diagram shown in Figure 3 (reproduced below). Why is the actor Guest associated with the use case for making a reservation but not associated with the use cases for checking in and out? The answer comes from an understanding of what happens when someone, a guest, arrives at a hotel. Hotels are service oriented. That is to say, they offer certain services to their guests with the intention of earning money for the business. A hote 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 6.2 Actors Iteration is a natural part of the modelling process. It does not matter whether you start by looking for the actors or the use cases. We have chosen to begin with the actors, since it is a way of expressing the system boundary implicitly and identifying the different views that need to be taken into account. In practice, you are likely to find that the actors are to be found in the roles that people play as employees in the problem domain, such as the hotel's receptionist or manager. A 6.1 Use case modelling In this section, we take a closer look at use case modelling, and show you how it can be used to model the requirements for a product that includes the development of a software application or, simply, a system. Use case models act as a discussion tool between the requirements analyst and stakeholders, and offer a common language for agreeing the functions of a proposed system. In this discussion, we shall use the Unified Modelling Language (UML) notation (diagrams) for use cases to re 5.1 More information about modelling techniques The four remaining diagramming techniques are described in separate sections below, which you should now study:
Exercise 5
Exercise 1
