[Year 12 SofDev] Resource flows in a DFD

[Mark Kelly]

Nor will I be including resource flows in DFDs, or even telling kids 
that non-data flows sometimes might appear.

Being bears of very little brain, they might be frightened by such 
complexities  :-)

Allan Barnes wrote:
> I agree, and I guess that is where theory merges with the realities of the
> real world. You have also alluded in other emails to the fact that there are
> often no exact definition of some areas such as the SDLC for example, so I
> think some of these concepts need to be explained to students not as the one
> and only explanation but as one possible solution.
> 
> I still believe that DFD's should not contain physical resources in them
> because then by definition it isn't a DFD, but that's just my opinion, but I
> do understand the difficulties and frustrations when opening up books and
> finding a variety of explanations for the one concept.
> 
> 
> 
> 
>    
> 
> Kind regards
>  
> Allan Barnes, CEO
> Australian Institute of Education and Training
> P.O. Box 171
> Brunswick West 3055
> Ph: (03) 9387 2051
> FAX: (03) 9387 3470
> Mobile: 0409 428 221
>  
> 
> -----Original Message-----
> From: sofdev-bounces at edulists.com.au [mailto:sofdev-bounces at edulists.com.au]
> On Behalf Of Mark Kelly
> Sent: Tuesday, 15 April 2008 10:45 AM
> To: Year 12 Software Development Teachers' Mailing List
> Subject: Re: [Year 12 SofDev] Resource flows in a DFD
> 
> Hi Allan.  Yes, I realise DFDs have usually only shown data flows, as 
> their name implies.  My concern was my research has found that physical 
> resource flows (such as real books) have been included in context 
> diagrams and DFDs.  That's the sticking point.
> 
> Allan Barnes wrote:
>> My understanding from Uni days is that DFD's are diagrams of logical
> systems
>> and represent flow of information. I don't quite follow what you mean when
>> you say a resource flow, Mark, but the DFD can in my opinion show things
>> such as book orders, for example, as this is a flow of information,
> however,
>> it would not show that it is Michael who has ordered the books, or that he
>> has ordered it over the phone, etc.
>>
>> The physical design provides information about how the processing takes
>> place. It may show who sends or receives the information, who manipulates
>> the data, where it is manipulated, what happens to it, what structure it
>> takes, whether the transaction occurs on the computer, the Internet, by
>> telephone, by cash register or by a paper-based method. The physical
> design
>> will also include details about the specifications of the hardware and
>> software that is to be used in the information system. It uses diagrams
> such
>> as hierarchy charts, structure charts and system flow charts to represent
>> the information.
>>
>>
>>
>>  
>>
>> Kind regards
>>  
>> Allan Barnes, CEO
>> Australian Institute of Education and Training
>> P.O. Box 171
>> Brunswick West 3055
>> Ph: (03) 9387 2051
>> FAX: (03) 9387 3470
>> Mobile: 0409 428 221
>>  
>> -----Original Message-----
>> From: sofdev-bounces at edulists.com.au
> [mailto:sofdev-bounces at edulists.com.au]
>> On Behalf Of Kevin Feely
>> Sent: Monday, 14 April 2008 4:49 PM
>> To: Year 12 Software Development Teachers' Mailing List
>> Subject: Re: [Year 12 SofDev] Resource flows in a DFD
>>
>> Hi mark,
>> In all of the exercises i have done with context diagrams (level 0) and 
>> DFD's (mainly level 1 and only discussion about level 2) i have always 
>> said only data (information) should be represented. That the DFD is not 
>> concerned with the actual goods ordered or purchased for example, but 
>> the information these transactions generate.
>> I suppose this is because we are modeling information systems using the 
>> DFD tool.
>> I suppose it is possible to model physical systems with the DFD as well 
>> ( obviously from your link!) but  iam not sure they should be intertwined.
>> That is if a student represents a physical transaction on my information 
>> DFD i would regard that as an error.
>> regards
>> Kev
>>
>> Mark Kelly wrote:
>>> I can't remember seeing a resource flow in an SD DFD, but apparently 
>>> they exist (e.g. 
>>> http://www.getahead-direct.com/gwba03-context-diagram.htm)
>>>
>>> Are they deliberately avoided in SD or are they not industry-standard?
>>>
>>> Cheers
>>> Mark
>>>
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-- 
Mark Kelly
Manager - Information Systems
McKinnon Secondary College
kel AT mckinnonsc.vic.edu.au
McKinnon Rd, McKinnon 3204, Victoria, Australia
Direct line / Voicemail: 8520 9085 Fax +613 9578 9253

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