Go with the Flow(Part 4)

3 Mar

Welcome back and I must say you are looking well today, well done! Now back to blog, so this week I will tell you technical side of DFDs. The bread and butter you might say. As you can imagine there’s a lot of crossovers between DFDS and flow charts but don’t worry I’ll explain everything

Again four symbols you need to know in order to make a DFDs.
• The external entity ( contains information from outside source that we could not have know prior to the DFD, represented by a oval)
• The logic flow ( The arrow, which shows the flow of Information from symbol to the next)
• The process ( where action is taking upon information that entered it )
• The Data store (the only symbol which isn’t in the flowcharts as you can guess where the data is …..)

The logic Flow arrow
DFD2

The Entity and Process
dfd1

And Finally the Data Store
dfd3

Processes “The magic box”
You must respect the rules of the processes otherwise you will have a very DFD. (I know the drama).
• All logic flow arrows must through the process box and out of it. Processes can mix with other symbols like external entities
Processes “The magic box” rules
You must respect the rules of the processes otherwise you will have a very DFD. (I know the drama).
1. All logic flow arrows must through the process box and out of it. Processes can mix with other symbols like external entities and data stores. But data stores can do not mix with other data-stores nor can entities, so only processes take and give out information.
2. DFD must have both internal and external relations. Other wise people will be mean and label these processes. Like if they have just inputs of information and no outputs, they call them a “black hole”, Ouch! Harsh. Or if the process has just if the process has no inputs but only outputs, “miracle”, now that’s just weird thing to call a process
3. This is why I call the process a magic box, it can transform data. When input goes in it comes out looking a bit more flash then when it entered e.g. input: new account status, goes into process box of memberships accounts then leaves as output: existing accounts
4. What you put in to a process you must get out evenly. No exceptions otherwise you must have to question whether the process took bribe or was threatened e.g. input: membership addresses, goes into process box of memberships accounts and then mysteriously comes out as a existing account?

And as usual you can’t cross data flow, but you can bring in more data stores and entities (you can’t bring in more of the same processes though, there one of kind!) . lastly, when using an entity all words inside them must be lower case as so not to confuse when the title of DFD which would be in Caps lock.

Wow this was my longest post to date. Tiring as you can imagine, but I couldn’t have done this without my Instructor notes http://cathaldoyle.com/ . Massive thank you instructor and stay tuned for part 5.


3 Responses to “Go with the Flow(Part 4)”

  1. sad111359681 March 5, 2013 at 10:24 am #

    thanks for the compliment, ur not looking too shabby yourself!

  2. sad111359681 March 5, 2013 at 10:25 am #

    oh and good post also!

  3. sad111490988 March 5, 2013 at 4:14 pm #

    Great Title and inspiring blog

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