[Year 12 SofDev] U3O2 module context diagram

[Esther Andrews]

So your issue is that you are producing a module that is part of a larger system.
The Context diagram for the larger system WOULD have the customer as an EE.
Your module would exist as part of that system and would appear as a single process in the level 1 DFD. You would have to expand that single process to a level 2 DFD to view the processes within that module, and that level 2 DFD would NOT have the Customer shown as a source of a dataflow.
That's too complex to explain to the students.
I'd simplify it for the students by drawing a context diagram for just that module (sans customer) or leaving them out all together as Adrian has recommended :)

From: sofdev-bounces at edulists.com.au [mailto:sofdev-bounces at edulists.com.au] On Behalf Of Mark KELLY
Sent: Monday, 9 May 2011 3:12 PM
To: Year 12 Software Development Teachers' Mailing List
Subject: Re: [Year 12 SofDev] U3O2 module context diagram

I'm tempted to use the simple version since dataflows between external entities (EE) is verboten.

The problem is that it implies that the customer directly provides data to the module, whereas the website and system pass the data on before the module becomes involved. The CD with the EE-to-EE flows would be more informative and accurate, but it breaks our rules...

It's a wrinkle I haven't faced before with context diagrams.
On 9 May 2011 14:31, Esther Andrews <ANDREWS.Esther at bssc.edu.au<mailto:ANDREWS.Esther at bssc.edu.au>> wrote:
Funny how the apparently simple can end up being complex.
Given your description I'd say the customer does not directly provide input into the system so should not be on the Context diagram.
Esther

From: sofdev-bounces at edulists.com.au<mailto:sofdev-bounces at edulists.com.au> [mailto:sofdev-bounces at edulists.com.au<mailto:sofdev-bounces at edulists.com.au>] On Behalf Of Mark KELLY
Sent: Monday, 9 May 2011 2:13 PM
To: Year 12 Software Development Teachers' Mailing List
Subject: [Year 12 SofDev] U3O2 module context diagram

Hi all. I',m adapting the detailed example of SD U3O2 from the study design for my own U3O2; I'm fiddling at the edges and not changing the overall shape of the example where the task is to create a specific module (cost calculator) in a larger ordering/accounting system that takes order data from a corporate website.


While getting into creating the SRS I thought the context diagram would be a doddle.  One external entity, the customer.  The system in the circle  is the cost calculator module.  One data flow from the customer with order information. One data flow to the customer with the invoice. Done.

Then I realised that from the module's perspective the rest of the ordering system might be seen as an external entity since the module has no control over the system's operation but must exchange data with it.

Then I realised that the system also would see the corporate website as an external entity for similar reasons. So the customer would interact with the website which would interact with the system, which would interact with the module that the students will be writing.

But if I showed the customer providing an order to the website, that would be a data flow between external entities which we are not supposed to show in a CD/DFD.

How would you guys interpret a situation like this?

--
Mark Kelly
Manager of ICT, Reporting, IT Learning Area
McKinnon Secondary College
McKinnon Rd McKinnon 3204, Victoria, Australia
Direct line / Voicemail: +613 8520 9085, Fax +613 9578 9253
kel at mckinnonsc.vic.edu.au<mailto:kel at mckinnonsc.vic.edu.au>
VCE IT Lecture Notes: http://vceit.com
Moderator: IT Applications Edulist

Want a good time? Call 0112358. Ask for Mr Fibonacci.

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--
Mark Kelly
Manager of ICT, Reporting, IT Learning Area
McKinnon Secondary College
McKinnon Rd McKinnon 3204, Victoria, Australia
Direct line / Voicemail: +613 8520 9085, Fax +613 9578 9253
kel at mckinnonsc.vic.edu.au<mailto:kel at mckinnonsc.vic.edu.au>
VCE IT Lecture Notes: http://vceit.com
Moderator: IT Applications Edulist

Want a good time? Call 0112358. Ask for Mr Fibonacci.
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