Question

1. Data Flow Diagram

The TOPCAR taxi company is developing a new computer system to be used to support taxi booking and corporate client credit accounts. This computer system aims to automate some manual processes and cut down on labour costs as TOPCAR has many customers from large corporate companies, e.g. CEO, and managers often need taxi trips to the airport. The following describes the activities that must be processed by the computer system:

A client company must first register and open a credit account with TOPCAR at TOPCAR’s website, in which case certain credit checks are made such as checking credit history of client company’s debt level. If the client company has no bad debt history, a credit account for the client company is set up.

At least 24 hours after successful account registration, authorized persons from such client company can request a taxi booking form TOPCAR’s website. When this happens, the availability of a taxi at the requested date and time is checked, as is the credit status of the client company checked. (Note that credit status in finance means a measure of a lender’s willingness to lend money to a particular person or organization, depending on their ability to repay).

If these two checks are successful, a booking is made, and a written confirmation is sent via SMS and emailed to client company. After the customer from the client company has used the taxi, the driver sends in a record of the work, including the cost, and this is added to client company’s account. (Note that driver is an outsourced worker from TOPCAR’s point of view.) At the end of each month, taxi bills are sent via SMS and emailed to client companies for settlement.

From the above description, draw a data flow diagram showing the flow of input information (and/or data) and output information (and/or data) to and from processes and database stores within this computer system and any external environmental elements that interact with this computer system. In this diagram, you must identify the following:

1. processes inside this computer system,                      
2. database stores, external environmental elements that interact with any of the processes identified

in (a)                                                 (5.5 marks)

3. input and output information (or data) to and from each of the processes, database stores, and external environmental elements identified in (a) and (b)        (7.5 marks)

(Hint: there are two environmental elements that interact with this computer system, and six main processes in this computer system)

Answer 1

can be automated by machines andfor computers as in business information systems:

In order to build and develop such automatic systems, these systems need to be designed properly by IT people (who know IT and computer knowledge, but not much about businesses) and business people (who know business operations in sales, finance, inventory, but not much in IT and computer).

Data Flow diagram (DFD) provides a graphical representation of how informationfdata moves between processes around a system, the way datafin‘formation is changed by processes and stored into databases. DFDs assist design and development of a system.

Objectives:

->to graphically document boundaries (main functions) of a system.

->to provide hierarchical breakdown of the system into smaller steps (or processes).

->I to show movement of information between a system and its environment (external entities) which interact (or exchange data and information) with the system.

->to document information flows within the system.

-> to aid communication between users of system and designers of system.

Components of a Data Flow Diagram [SSADM notation]:

We are now going to look inside the box and diagrammatically represent the processing of the inputs to the system to get the outputs from the system. We are going to use the following notation (this is SSADM notation - the most popular system development, it's used by the Government).

a) Information Flow :

A data flow can be thought of as a pipeline through which packets of data of known composition flow. Data flows must be an input or output of a Process Box. Physical flows are sometimes represented by a dotted line.

b) Process (performed by the CPU): Process Identifier (A Number) salaries Place Where Process Done, or Produce Person who does it (Only Used in Physical DFD) Payroll The Actual Process Process Symbol Each process transforms incoming data flows into outgoing data flows. Each process can / should be documented with a brief function description, a brief outline of the processing activity which is taking place.

An example DFD using all Components:After a service job is finished, a service engineer returns a service job description (either written on paper or typed on an electronic device via computer or phone) to the system for recording process and purpose, and this recording process checks any error in input and will store the service job description into the database.

Hints for Drawing Data Flow Diagrams :

#avoid detail initially.

#identify external entities - they provide the boundary.

#identify main processes, then concentrate on data flows.

#ensure enough data flows go into a process to perform the process.

#ignore timing, except for logical procedures.

# duplicate external entities and data store to improve clarity of diagram.

#use meaningful names.

#do not duplicate data flows.

#be prepared to modify and re-draw.

An example DFD in real life :Below is the data flow diagram for Electrical World. This shows the processes in the system.~ These processes reflect the basic operations in Electrical World, the data flow arrows into and out of each process show the necessary required data (or information) for each operation, and the resulting data (or information) from each operation.

a.)

Service job return work job desc Record Service service projection 2 service History engineer Allocate D1 service job sheet Maintain Time service equipment 3 DZ work schedule work time history Assign Maintain available Slot working day product supplier maintenance details request 4 sales product customer paybook product D3 product details contract details Maintain details confirm Product Details enquiry 5 sales despatch note credit despatch note request Agree Contract proform a delivery b stock despatch note despatch section credit details 6 warehouse note agency credit update D6 stk available customer Assign Item to stock Customer despatch details details stock D5 stock D4 customer details payment 10 warehouse Update Stock stock voucher Available Record 9 warehouse receipt details 7 accounts Add to stock Stock receipt Update h payment Account purchasing voucher goods received system note a accounts warehouse, clerk recovery customer notice note D4 customer 8 sales cancellation End Contract.

b.)

customer requested items Searching + Selection catalogue of catalogue items catalogue Selected items cdispatch Verify availability product availability letter of selected items information ainventor credit file checked order Process credit card credit cards pay ment request Bank Process payment confirmation approval of credit payment paid paid order items order warehouse.