Question

What are the guidelines to be followed when you draw a context diagram and other data flow diagrams (DFDs)?

Answer 1

Context digram

The context digram contain the single high level process it used to show the relationship that the system has with other external entities.context diagram also known as data flow digram as level-0.context digram is created for the system analysis and design.it can showing system as whole and its input and output form.it used to show the interaction between a system and other factors with the system.

The below picture contain the example of context digram

Show this the context digram for the online food ordering system

The main imports things are in the digram are contain the notation that they are simply contain the boxes and lines.it is developed using 2 types that conatin one conatin the circle this conatin in the center and it is the main representing the system in the image online food order system system it shows the system representing.after that it conatin the multiple boxes for each external factors and relationship.and other is conatin the labeled line between the entries and the system.the circle known as processes and other contain the external entities  that it conatin in the rectangle which shows you a given process or activity.this can be used to receive the output from the process.so in this digram contain the three external enties that three modules admin,hotelowner and the last one is user.and the other contain the data flow that is arrow they are conatin the connector between main process and various entities. The arrow indication is import it showing the process.so in this digram user can going to login into the system.he can select hotel he can make the payment for his food.in the other case you can see on the admin entities the arrow are towards the eneties .that means that he has rights to view all the detail.he conatin main modules for the system.the direction of arrow are showing the flow of system.see as you seen the digram where this shown overall process of system.

DFD

dfd stand for data flow digram.it is used to show flow of information for any process or system.

The below picture of dfd for specific for user module

When going to draw a dfd we need keep in mind that one process needs at least one input and output as in digram user is conatin the process so this conatin the multiple input and output shown by using dataflow symbol.each data stored should have at least one dataflow and one dataflow out in the digram datastore is contain  the database table where it have multiple dataflow like login details,hoteldetails..data stored in the system must go through a process you can see in the picture all dataflow goes through the system..all processes in dfd need to go on another process or data store.

.on this defined symbol that rectangle circle and arrow.contain external enties means rectangle in this digram the user conatin the entries that shows the system that send or receive the data and it communicate with system because here user can sending and receiving the data.. Process contain the circle.process that changes the data and producing an output here process contain in the image that login,shopping cart it providing some activites on that were the user is performing. .a short label used to describe the process like you can see select hotel,select hotel details..data stores that hold that data for after use this conatin tha table as you can say database table were you can acess the information from that here provided in the digram that hotel details,menu details, and other one symbol is conatin the data flow that is arrow where it used that route the data take between external enties ,process. In the digram user going to login first to the system after that he can select the hotel.after he can select which menu he want.after he can add it to the cart and makes the payment this contain the process where shown in the digram It conatin goes specific user modules.