DATA FLOW DIAGRAM (DFD)

Data flow diagram (DFD) is used to show how data flows through the system and the processes that transform the input data into output. Data flow diagrams are a way of expressing system requirements in a graphical manner. DFD represents one of the most ingenious tools used for structured analysis. It is also known as a bubble chart.

In the normal convention, logical DFD can be completed using only four notations.

The DFD at the simplest level is referred to as the ‘CONTEXT ANALYSIS DIAGRAM’. These are expanded by level, each explaining its process in detail. Processes are numbered for easy identification and are normally labeled in block letters. Each data flow is labeled for easy understanding.

Steps to Construct Data Flow Diagrams

Four steps are commonly used to construct a DFD

1. Process should be named and numbered for easy reference. Each name should be representative of the process.

2. The direction of flow is from top to bottom and from left to right.

3. When a process is exploded in to lower level details they are numbered.

4. The names of data stores, sources and destinations are written in capital letters.

Salient feature of DFD

Q The DFD shows flow of data, not of control loops and decision are controlled considerations do not appear on a DFD.

Q The DFD does not indicate the time factor involved in any process whether the data flows take place daily, weekly, monthly or yearly.

Q The sequence of events is not brought out on the DFD.

Behavioral feasibility

People are inherently resistant to change, and computers have been known to facilitate change. An estimate should be made about the reaction of the user staff towards the development of a computerized system. Computer installations have something to do with turnover, transfers and changes in job status. The introduction of a candidate system requires special effort to educate, sell and train the staff for conducting the business.

The candidate system was found to be technically, economically, and behaviorally feasible. The system was developed user friendly, needless training and improves the working environment. Justification for any capital outlay is that it will increase profit, reduce expenditure or improve the quality of service or goods, which in turn may be expected to provide increased profits. Disregarding the initial expenses, the candidate system was assessed to be feasible in all ways.

Technical feasibility

The assessments of technical feasibility centers on the existing system and to what extent it can support the proposed addition. This was based on an outline design of system requirements in turns of inputs, files, programs, procedures, and staff. It involves financial considerations to accommodate technical enhancement.

Economic feasibility

Economic analysis is the most frequently used method for evaluating the effectiveness of a candidate system. It is more commonly known as cost benefit analysis, the procedure to determine the benefits and saving that are expected from a candidate system and compare them with costs. If the benefits outweigh costs then a decision is made to design and implement the system. Otherwise make alterations in the proposed system.

FEASIBILITY ANALYSIS

Feasibility analysis is the procedure for identifying the candidate system, evaluating and electing the most feasible system. This is done by investigating the existing system in the area under investigation or general ideas about a new system. It is a test of a system proposal according to its workability, impact on the organization, ability to meet user needs, and effective use of resources. The objective of feasibility study is not to solve the problem but to acquire a sense of its scope. Feasibility analysis involves the following steps:

Ø Form a project team and appoint a project leader.

Ø Prepare system flow charts.

Ø Enumerate potential candidate system.

Ø Describe and identify characteristics of candidate systems.

Ø Determine and evaluate performance and cost effectiveness of each candidate system.

Ø Weigh system performance and cost data.

Ø Select the best candidate system.

Ø Repair and report final project directive to management.

Three key considerations are involved in the feasibility analysis:

R Economic

R Technical

R Behavioral.

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