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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Me again. Sorry.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>A data store is where data is stored (sounds silly doesn’t
it?).<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>A data store is therefore worthless if data is not written to it
and taken from it, but it can still exist as a data store. There just is no
point to it and it would be considered poor design. Consider – if no ‘new’
or ongoing data is written to a data store then you can only take limited
information out of it as no new information will be sent to it. If you don’t
take information out of it then what is the point of saving information to it? In
this example, you can’t take customer orders from the data store if the
waiter does not save the orders to the system. So the data store needs data to
be saved to it in order for the chef to retrieve it.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If it is written to system 1 and then read from system 2, the information
would therefore need to be sent from 1 to 2 (begging the question why?). <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I would have thought that as the text file holds data it
therefore needs to be displayed as a data store in the DFD. Or two. At level 1
DFD I think you can only show 1 system by definition (?), if you go to a Level
2 DFD which I don’t think is required at Year 12 level, you would show
the 2 systems.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Kind regards<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Allan Barnes, CEO<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Australian Institute of Education and Training<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>P.O. Box 171<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Brunswick West 3055<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Melbourne, Victoria<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Ph: (03) 9387 2051<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>FAX: (03) 9387 3470<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Mobile: 0409 428 221<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> sofdev-bounces@edulists.com.au
[mailto:sofdev-bounces@edulists.com.au] <b>On Behalf Of </b>Mark KELLY<br>
<b>Sent:</b> Friday, 29 July 2011 9:37 AM<br>
<b>To:</b> Year 12 Software Development Teachers' Mailing List<br>
<b>Subject:</b> [Year 12 SofDev] A DFD theory challenge!<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'>Hi all. As I ponder the Mexican
Cantina detailed example of SD U4O1 in the study design, I find the DFD
increasingly interesting.<br>
<br>
The case study says that the student's mobile software (call it system 1)
writes an order to a text file.<br>
The other software (call it system 2) reads the text file and transmits it to the
kitchen.<br>
<br>
The question is: Is the text file a 'data store'? What constitutes a data
store? <br>
Does it need to be both written to and read to qualify as a data store?<br>
Does it need to be written/read by the <b>same</b> system?<br>
Or can it be read/written by 2 systems?<br>
If it's only written by system1, and then left somewhere to be read by system
2, does it still count as part of system 1?<br>
<br>
Therefore: Should the text file be shown as a data store in the DFD?<br>
Should system 2 be shown as an external entity getting input from the text
file?<br>
Will Saint Kilda get into the final 8 this season?<br>
<br>
Draft DFD attached.<br>
-- <br>
Mark Kelly<br>
Manager of ICT, Reporting, IT Learning Area<br>
McKinnon Secondary College<br>
McKinnon Rd McKinnon 3204, Victoria, Australia<br>
Direct line / Voicemail: +613 8520 9085, Fax +613 9578 9253<br>
<a href="mailto:kel@mckinnonsc.vic.edu.au" target="_blank">kel@mckinnonsc.vic.edu.au</a><br>
VCE IT Lecture Notes: <a href="http://vceit.com" target="_blank">http://vceit.com</a><br>
Moderator: <a href="http://www.edulists.com.au/" target="_blank">IT
Applications Edulist</a><br>
<br>
Want a good time? Call 0112358. Ask for Mr Fibonacci.<o:p></o:p></p>
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