Software Architecture Design: Transform Mapping

Instructor: Meghalee Goswami

Meghalee has a masters of computer science and communication engineering.

In this lesson, we are going to learn how Data Flow Diagrams will be converted into characteristics of a system using transform mapping. We will use symbols as well as various representations to transform a data flow diagram into system characteristics.

Transform Mapping

Transform mapping is a technique in which Data Flow Diagrams (DFD's) are mapped to a specific scenario. It is a data flow-oriented mapping technique that uses DFDs to map real life scenarios to a software architecture. These real life scenarios are converted to what we call DFDs which can be applied to a software architecture. This process of converting a real-life situation (termed as system in software engineering) with flow of data to a DFD is called transform mapping. In this lesson, transform mapping has been described using the scenario of an airline reservation system.

Data Flow Diagram

A Data Flow Diagram(DFD) shows the flow of data through the system. It is also used for modeling the requirements. DFD is often called as a data flow graph. The data flow diagram is created with the help of various symbols which represent a process, data repository etc.

Symbols used in DFD


This symbol denotes a process which transforms data input into data output
Circle



This symbol depicts the data flow, it shows flow of data into or out of a process or data store.
null



This symbol depicts a source or sink. It is an external entity that acts as a source of system input or system output
Rect



This symbol depicts a data repository, a place where collection of data items are stored.
Db



Alternatively used for data repository
data repo


Example of Transform Mapping

See the figure below. This is a depiction of DFD level 0 where an architecture of an airline reservation system has been shown. The customer supplies trip details and payment mode as an input to the Airline reservation system. Airline reservation is a process which provides flight availability as well cost as an output to the customers which is a source in this case. This is the level 0 hierarchy of the DFD's.


DFD level-0
DFD0


The next figure shows DFD level-1. You can see a repository named Flight database where the details related to seat availability are stored. This information is displayed on the website of the reservation system which informs the customer how many seats are available on the flight. Customer retrieves the details from the website after providing the specification of the trip details during the 'Retrieve and Display' process. 'Seat Reservation' is a process which is indirectly connected to another process called 'Total Cost Calculation'. This process helps in calculating the cost for the number of seats requested. The cost details are then provided to the customer based on the number of seats reserved which is indirectly provided by the process 'Seat Reservation'. 'Ticket Generation' is a process which generates tickets once the customer provides the payment details. The input for this process is payment and the output of this process is the E-ticket. 'Cancellation' is another such process which cancels the ticket of a customer when the customer provides the E-ticket, the output from the process being an acknowledgment sent back to the customer.


DFD level-1
DFD1


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