[Year 12 SofDev] U3O2 module context diagram

[Esther Andrews]

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] 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
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Direct line / Voicemail: +613 8520 9085, Fax +613 9578 9253
kel at mckinnonsc.vic.edu.au<mailto:kel at mckinnonsc.vic.edu.au>
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