WORKED EXAMPLES ON DATA FLOW DIAGRAMS.

By -

DATA FLOW DIAGRAMS

WORKED EXAMPLES

5.1 What is the main merit of DFD?

The main merit of DFD is that it provides an overview of what data flows in a system, what transformations are done on the data, what files are used and where results flow.

5.2 What is the role of DFD as a documentation aid?

It is a good documentation aid which is understood by both programmers and non-programmers (i.e., laypersons). As DFD specifies only what processes are performed and not how they are performed it is easily understood by a non- programming user.

5.3 What is a context diagram?

A diagram giving an entire system’s data flows and processing with a single Process (circle) is called a context diagram.

5.4 What do you understand by levelling of DFD?

A context diagram is expanded into a number of inter-related processes. Each process may be further expanded into a set of inter-connected sub processes. This procedure of expanding a DFD is known as levelling.

5.5 What is a physical DFD?

A physical DFD specifies from where data flows and who processes the data and to whom the processed data is sent.

5.6 In what way is physical DFD useful?

It is easy to develop during fact gathering stage of systems analysis. Such a physical DFD is easily understood by a lay user who can verify the DFD drawn by an analyst and tell whether such a DFD corresponds to a particular operation taking place in an organization. Physical DFD is the starting point for developing the logical DFD.

5.7 What are the mistakes in each of the DFDs of Fig. 5.7(a)–5.7(e)? Correct these mistakes.

image

image

(i) To compute gross pay we need hours worked and hourly wage rate. This data flow is missing.

(ii) A data flow cannot have two arrows pointing in opposite directions. A separate data flow line should be drawn for “application returned”.

(iii) A data flow connects two distinct data stores without an intermediate processing step. (See also answer to Exercise 7.5)

(iv) Process P2 has all input data flow and no output data flow.

(v) The same data flow cannot be given two names.

Comments

Post a Comment

Popular posts from this blog

WORKED EXAMPLES ON PROCESS SPECIFICATION.

By -
Image
PROCESS SPECIFICATION WORKED EXAMPLES 6.1 A bank has the following policy on deposits: On deposits of Rs. 5000 and above and for three years or above the interest is 12%. On the same deposit for a period less than 3 years it is 10%. On deposits below Rs. 5000 the interest is 8% regardless of the period of deposit. Write the above process using (i) Structured English (ii) A decision table 6.2 An organization maintains an employee file in which each record has following data: { Employee No., employee name, employee gross pay}. It has been decided to increase the pay as per the following formula: For pay of Rs. 1000 or less increase 15%. For pay of more than Rs. 1000 but up to Rs. 2500 increase 10%. For pay over Rs. 2500 increase 5%. (i) Writ e a structured English processing rule corresponding to the above policies. (ii) Express the policies as a decision table. (i) While employee records left in file do Read Number, name , gross pay 6.3 An offshore gas company bills it
Read more

Why do we need information systems, management structure, requirements of information at different levels of management.

By -
Image
Why do we need information systems, management structure, requirements of information at different levels of management NEED FOR INFORMATION SYSTEMS Information systems are needed when timely processing for fast action is needed, same data has to be processed in different ways and when organizations require innovative processing. MANAGEMENT STRUCTURE Functional areas of management are as follows: •PRODUCTION • MARKETING • MATERIALS – purchase, stores • FINANCE –Accounts • HUMAN RESOURCE DEVELOPMENT(HRD) • RESEARCH AND DEVELOPMENT (R&D) INFORMATION FOR MANAGEMENT A Production Management The following type of information is needed in production management: Strategic Information: 1)Yearly and monthly production quotas and alternate schedules 2)Policies on machine replacement, augmentation and modernization. 3)Identifying best product mix. Tactical Information 1)Identifying and controlling areas of high cost. 2) Identifying critical bottlenecks in production. 3)
Read more

The User Interface:Establishing User Interfaces

By -
Image
The User Interface Establishing User Interfaces The success factors in analysis start with the established interfaces from day one. What does this mean? You must start the process by meeting with the right people in the organization. In the best projects, the process is as follows: 1. Executive interface: There needs to be an executive-level supporter of the project. Without such a supporter, you risk not being able to keep the project on schedule. Most important, you need a supporter for the political issues that you may need to handle during the project (discussed in detail later). The executive supporter, sometimes known as a sponsor (JAD reference), should provide a preliminary schedule advising the organization of what is expected and the objectives of the project. The executive supporter should attach a letter to the preliminary schedule and send it to the project team members. The letter must put the importance of the project into perspective. Therefore, it is strongly rec
Read more