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Can an external entity be a data file? (1 Viewer)

MrBrightside

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I've done some research and I found these facts. By data file, I DON'T mean data store, I mean a particular file that communicates with the process.

Dos and Don’ts of external entity
· External entity never communicate with each other, this signify that there is no need for the process
· External entity should not communicate directly with data store because external entities can be identifier with the record of files and databases

http://oderog.hubpages.com/hub/What-is-a-data-flow-diagram

There was a MPC question in this years paper and it included a data file in the external entity box. I wanted to know if this is right or wrong. Thank you.
 

MrBrightside

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I know which question your talking about, I put 'A' as well, but I think it was foolish:

"Data stores are repositories of data in the system. They are sometimes also referred to as files."
http://www.smartdraw.com/resources/...sources/tutorials/Data-Flow-Diagram-Notations
Yes, I'm feeling exactly what you're feeling lol. I still don't know if BOS was trying to make a trick question and A was the correct one OR If they were hoping a lot of people would pick A as the incorrect choice due to it displaying more detail :(

"External Entity
External entities are objects outside the system, with which the system communicates. External entities are sources and destinations of the system's inputs and outputs." Hmmm from your website there, that could possibly mean it is a file, as the system communicates with it and it did give a Student ID to the file so that's input :/ omg it's a 1 mark question and I can't get it out of my head!!.

Right now I'm feeling that B (without the file) was 80% correct and A(with the file in the external entity) was 20% correct. lol I hate these questions, over my two years of IPT I had never seen a question like this or the knowledge behind to back it up. I learn something new every time I look at a context diagram.
 
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mathemalia

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Yes, I'm feeling exactly what you're feeling lol. I still don't know if BOS was trying to make a trick question and A was the correct one OR If they were hoping a lot of people would pick A as the incorrect choice due to it displaying more detail :(

"External Entity
External entities are objects outside the system, with which the system communicates. External entities are sources and destinations of the system's inputs and outputs." Hmmm from your website there, that could possibly mean it is a file, as the system communicates with it and it did give a Student ID to the file so that's input :/ omg it's a 1 mark question and I can't get it out of my head!!.

Right now I'm feeling that B (without the file) was 80% correct and A(with the file in the external entity) was 20% correct. lol I hate these questions, over my two years of IPT I had never seen a question like this or the knowledge behind to back it up. I learn something new every time I look at a context diagram.
Just the fact it said 'file', its a downer, but oh well man, hopefully we'll be all right :D

and lol i exactly know what you mean by caring about those little marks...!
 

splash_me

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The answer should be B.

A general rule about external entities is that they must be 'an intelligence', meaning that they represent people. A timetable file is a data store so it should not appear on a context diagram.
Entities don't store data like a data store, they just supply inputs and receive outputs from the system.
 

debragail

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Was the diagram a context diagram or a DFD? (Don't have the paper on me.)

I believe that it was an error in the paper.
 

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