10 Techniques and tools for system

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1 10 Techniques and tools for system development AQA Unit 3 Section 9 Over the years, various methods have been developed to help the creation of new information systems. Often, these methods have been developed and then improved as a result of mistakes and systems that fail to do what they should do. Investigating and recording techniques We saw in Chapter 9 that there are four main ways of investigating how a system works at present: interviews questionnaires observation document analysis. 136 Interviews It is important to interview key members of staff such as managers and users. The systems analyst should be a good listener. The information is flowing from the member of staff to the analyst not the other way round. There should be no leading questions, such as Why do you think your computer system is so bad? or Your computer system is rubbish, isn t it? Questions should be neutral, such as, Can you tell me what you use the computer for? The analyst should not ask, Do you think the work could be done more easily by a new computer? It is the analyst s job to find out! The analyst should take notes and show them to the interviewee to make sure that they have got the details right. Questionnaires Questionnaires are likely to be used where there are a very large number of users. There may not be time to interview everybody but it is still a good idea to interview the most important ones. Questionnaires can include: open questions: questions with no specific answers in mind closed questions: questions where the user chooses an answer from a list.

2 It is much easier to analyse the answers to closed questions but users may not always find a suitable answer on the list. Observation This simply involves watching users do their jobs, writing down what they do and looking for problems such as bottlenecks in the system. As the analysts are independent, they are not looking for something specific. Sometimes, someone seeing a situation for the first time can immediately spot something that the users have never considered to be a problem. Document analysis This means looking at existing documents such as business forms, reports, records, orders, invoices, diaries, etc. Document analysis helps the analyst to understand: what information is used who uses it where the information is stored how the information is stored how long the information is used for. Business process modelling tools As with observation, inefficiencies in the current system may be spotted straightaway by looking at documents. If a new system is to be developed, the new documents should be as similar as possible to the old ones so that users are comfortable with the new documents. Business process modelling tools Diagrams can be used in the modelling of business processes. Like graphs, they enable anyone looking at them to get a picture of what is happening. Diagrams are often much quicker and easier to understand than the same information in text format. You are probably familiar with Gantt charts and flowcharts. Gantt charts (named after their inventor Henry Laurence Gantt) are used to show project timetables and schedules. Flowcharts use lines and symbols to indicate the flow of data or the sequence of operations. Another example of a business modelling tool is Business Process Modelling Notation (BPMN), which is a graphical representation of workflow in a business. BPMN helps process management by representing complex processes in intuitive diagrams. You can use the Internet to download free software for the easy creation of BPMN diagrams (see Figure 10.1). Find out more about BPMN at: 137

3 TECHNIQUES AND TOOLS FOR SYSTEM DEVELOPMENT Travel reservation Credit rating approved? Yes Book hire car No Book flight Refusal letter Confirmation letter Figure 10.1 A BPMN diagram Project managers have for a long time used Gantt charts (see Figure 10.2) to represent a project plan specifying tasks, resources and dates. Today they are likely to use project management software such as Microsoft Project or OpenProj to produce the diagrams for them. Find out more about Openproj at SSADM and PRINCE2 are two commonly used methodologies for managing projects: Structured Systems Analysis and Design Methodology (SSADM) was developed to provide a standard methodology for developing UK Government IT projects. It uses a set of structured techniques and tools to study data flows, data models and lifecycles. PRINCE2 is a structured methodology aimed at the successful management of a project, using procedures to manage budget, time, risk and quality. 138

4 Time in months Preliminary study Feasibility study Produce draft designs Consult with client and prepare second designs Build prototype, show to client Finalise designs, get client approval Create solution Test solution Produce documentation Business process modelling tools Implement solution Monitor solution Figure 10.2 A Gantt chart case study 1 Reading Borough Council (Source: case_studies/reading.pdf) Reading Borough Council provides services for 144,000 residents and employs 5500 staff. From 2000, all councils had to make their services available electronically. For example, residents should be able to book a badminton court online. Providing such services electronically is known as e-government. Councils provide a large number of services, such as schools, roads, parks, housing benefit and recycling. So, introducing e-government was a huge task. As a result, the informal project management methods used previously would not have been suitable. Reading Borough Council decided to use formal project management methods and, in particular, the PRINCE2 methodology. The benefits of using PRINCE2 include: The methodology is flexible and allows iterative methods. There is a common approach which is easily understood and communicated to staff. The common approach means that staff can be swapped over easily and knowledge is not lost when people leave. Lessons learned can be passed on. Workloads can be better managed. Project documentation is easy to access. Risks can be identified and managed. 139

5 TECHNIQUES AND TOOLS FOR SYSTEM DEVELOPMENT case study (contd.) Data modelling tools Auditing is easier. Find out more about PRINCE2 from List the main features offered by PRINCE2. Diagrams are also used in data modelling. You will need to understand diagrams and tools used in the modelling of business processes, such as entity relationship diagrams and data flow diagrams. Entity relationship diagrams Entity relationship (ER) diagrams are used in designing relational databases. They show the relationships between the data in different tables (the entities). A booking system in a driving school may look like Figure The crow s feet indicate that a student can have many appointments but an appointment would normally only have one student. This is a one-to-many relationship. Similarly, an instructor can have many appointments, but an appointment would normally only have one instructor. This is also a one-tomany relationship. Appointment Instructor Figure 10.3 Entity relationship diagram for a driving school The relationships between tables and how they are linked is shown diagrammatically in Figure

6 Data modelling tools Figure 10.4 Tables for a driving school D2 External entity Process Data store Flow of data Figure 10.5 Data flow diagram symbols Data flow diagrams Data flow diagrams (DFDs) show the movement of data through the whole organisation. DFDs are used in systems analysis to show how data moves through a system. The symbols shown in Figure 10.5 are used in data flow diagrams. External sources of information and external recipients of information are called external entities. They are usually people such as customers, suppliers and users of the system. In the driving-school system, there are two external entities: the student and the instructor. Level 0 context diagram The first diagram is the context diagram. This is very much a high-level overview of the system. Drawing a level 0 diagram starts with a rectangle in the middle of an A4 piece of paper. This rectangle represents the system. Next to it, oval shapes represent the external entitles (see Figure 10.6). 141

7 TECHNIQUES AND TOOLS FOR SYSTEM DEVELOPMENT Figure 10.6 Starting a level 0 context diagram membership number changes in test results lesson date and time Pass-It System Instructor Arrows show each of the data flows. It can help to make a list of all the data flows in the system. For example, when a new student joins the driving school, the external entity who is the source is the student. The arrow flows from the student to the system. For each of the data flows, an arrow in the data flow diagram shows where the data is flowing. The finished level 0 diagram looks like Figure The arrows should correspond to the data flows identified. Pass-It System changes in timetable lesson cost Instructor cancellation details Figure 10.7 Complete level 0 context diagram Level 1 diagram At level 1, the DFD is broken down by dividing the processes into individual, more detailed, numbered processes. The DFD shows incoming data flow, outgoing data flow and the associated processes. Each process refers to a separate part of the finished system. In the case of the Pass-It system, the four processes are student administration, lesson booking, instructor administration and general administration (see Figure 10.8). Note that an external entity may appear more than once in a DFD. The diagonal line inside the oval shape shows that the entity appears elsewhere. The data stores are labelled D1, D2, etc. in Figure Each data store represents a table in the final system. 142 As data will be both written to and read from each data store, there must be at least one arrow going into each data store and at least one arrow leading from it. Data cannot flow directly from a data store to an external entity, only via a process.

8 changes in test results 1 Administration student details D1 File Data modelling tools lesson date and time cancellation details timetable 2 Lesson Booking requirements availability booked lesson details instructor details D2 Lesson File Instructor changes in 3 Instructor Administration D3 Instructor File membership number lesson cost 4 General Administration updated prices prices D4 lesson Type File Figure 10.8 Level 1 data flow diagram It is possible to go further and create level 2 diagrams, breaking the system down further into the various processes involved. Each process has its own DFD. However, we do not need to go this far for this course. Data flow diagrams can be drawn in different ways. However you draw them, it is essential that the way you present your diagrams is consistent and that they have a key. 143

9 TECHNIQUES AND TOOLS FOR SYSTEM DEVELOPMENT Techniques for testing Rules for DFDs There should be a data store for every entity. Information flows show data and not physical items. Entities don t link directly to data stores. What goes in must come out. There is a range of different testing techniques available to software developers. Here we look at a few examples: A test harness is a collection of software and test data configured to perform specific tests on a module of a program by running it under different conditions, comparing actual outputs with expected outputs. Volume testing tests that the new system works with large volumes of data. After a long period of use, data files may become very large. Volume testing tests that this does not affect the performance of the software. Scalability testing tests that a system will still perform as required even if the system has to deal with an increased workload such as increased numbers of users, large numbers of transactions, increased numbers of files and large volumes of data. Prototyping means producing a scaled-down, simple version of the software which is used to show how the new system will work. The prototype can be constructed and tested in a short time. Multiplatform testing ensures that software can be used with a variety of hardware specifications and operating systems. For example, new browser software for a PC should work in both Windows XP and Windows Vista. Clearly, new software will need to be tested with a variety of hardware and software before it can be released commercially. Simulated environments with various inputs and outputs can be used to test software in as realistic an environment as possible. 144

10 SUMMARY The four main ways of investigating a system are: interviews questionnaires observation document analysis. Modelling tools can be used to illustrate: business processes entities and relationships data flow. Summary 145

11 TECHNIQUES AND TOOLS FOR SYSTEM DEVELOPMENT Questions 1. Southside College is going to implement a facilities booking system (see AQA-INFO3-W-SQP-07.PDF, page 4). One of the first tasks for the systems analyst is to produce a diagram of the context in which the facilities booking system will sit within Southside College. Draw a fully labelled context diagram for the facilities booking system, showing external entities and information flows. (8) Specimen paper 3 2. The systems analyst for Southside College has looked at the data required by the booking system and has found that the following rules apply: Any person or group can make a number of bookings. A booking is for one hall only (either the sports hall or the multi-functional hall). A booking may require many items of equipment. Each item of equipment belongs to one hall. Complete the entity relationship diagram in Figure 10.9 to show these relationships. Label all relationships. (8) 3. A company is introducing a new e-commerce system selling designer sunglasses over the Internet. Name and describe two testing techniques that would be appropriate. (4) 4. A friend of yours has ordered new software from a programming company. She has been told that the programmers will create a prototype. She has sent you an asking you what is meant by prototype. Compose an answer for her. (3) 5. What is meant by document analysis and what is its purpose? (3) Customer makes Booking Hall many Booked Equipment Equipment Figure 10.9 Incomplete entity relationship diagram 146