Tools of Analysis (part 6 of 8) - Process & Data (DFD / Data Flow Diagram)

[mahinthan5]

External entity must be circle and process must be Rectangle..

[gvimontslice]

@mahinthan5 Dr. Langer is using the Yourdon/DeMarco method for data flow diagrams. In this case, the external symbol is a rectangle and the process symbol is a circle or ellipse.

[m33taphor]

i believe that when placing a data flow you must label the data flow

[gvimontslice]

@m33taphor The convention for Yourdon/DeMarco DFD symbols is to only name explicitly the flows between externals and processes and those that flow among processes. Notice that these types of flow are uni-directional, thus the name will be clear as to the aggregation of data elements within each uniquely named flow.

[gvimontslice]

@m33taphor The convention for data stores is to leave these un-named because these may be bi-directional (read/write) and the details of what is being read and written will be defined within the process specification.

[mogra671]

We need this tutor in Bolton uni ours is dumb and trying to show her self number one tutor. for system analysis. tnx ur lecture sud be awesome .

Thanks for this video

[CorporateG0th]

1:10 yes, but reading data rather than writing it can be a process too.

[gvimontslice]

@CorporateG0th -- It can be challenging to differentiate between business processes and intrinsic systemic services. DFDs are most useful in modeling flows of information (in the form of data elements) among processes and between their related sources (points of origin) and sinks (targets). The bottom line remains, if the data is not changed or manipulated in some manner, there really is no meaningful process.

[CorporateG0th]

@gvimontslice

Depends, the data read can be used for other functions down the line. An example is given in this video, with process "Send invoices" having read-only access to the "Invoices" datastore, as indicated by the arrow leading away from the datastore rather than to it.

I just felt I should comment on that dual nature given that he describes processes as entities that mutate data earlier on in the video.

[mogra671]

very,,,,, good explanation 

[JaxxDaemon]

This is very interesting :)

[standman007]

Really fantastic. Exactly what i wanted

[Faisdragon]

that one video was equivalent of around 100 slides, 2 chapters and a full lecture worth. Maybe I should make a DFD of that :D

Great video.

[parthasawant]

@Faisdragon I agree

[KernelThread]

Some consider the circle as an external entity and the rectangle as the process... 

[gvimontslice]

Langer is using the Yourdon / DeMarco data flow diagram (DFD) methodology that uses a very simple set of symbols in a consistent and easy to understand manner. On the other hand, process flow diagrams (PFD) often follow the symbol style you’ve referenced.

[KernelThread]

@gvimontslice Thanks, that is interesting..

[unclegholam]

thank you

[fatmamansour19]

very good video

[Qalkux]

that was a good vid this helps me alot with my exam 2moro thanks very much

[bubinhoballer]

nice vid

[dudel3ss]

he explained it in a very simple way..thank you so much

[daambassador1]

Art: I owe you a pint if I ever meet you ;)

[Hazuki192]

great videos, should help my exams :)

[Haidersr]

very well explained, thank you much... I though agree that the board would be a little clearer...

[Gal19new86]

agreeed. Board could be a little clearer but the delivery of the content was excellent. Well done.

[jetblack2]

Well done finally someone that can describe a dfd and not a flow bloddy chart lol, the board could be a bit clearer but well done !!!