[Year 12 SofDev] Exam discussion - Edited

Fri Nov 16 23:21:53 EST 2007

Hi Kevin,

It is humbly and respectfully also that I say we are in agreement I am sure.
Let me explain. Oh no there he goes again ..... I hear you sigh !

( I have to confess I am writing from home and the exam paper is not in 
front of me so forgive any oversights )

When constrained with only 1 remaining external entity on the context 
diagram and there is a case for both retail and wholesale customers to 
purchase products from the bakery, then drivers alone could not be deemed to 
be the link between ALL orders and the system.

Also, if the drivers were shown to do some processing such as when 
collecting the order form and validating all data entry as  then yes, 
absolutely, there would have to be a connection between drivers and the 
system and being INSIDE the system would not do as they have a role in a sub 
process called "validate order". However, I didn't see such a role for the 
drivers from my reading and when faced with one final external entity to 
include I went for the more general order source being "customer".

 Also, let me correct the "physical" process meaning. Buying flour, 
ingredients etc is a physical process but the DFD would concern itself with 
the "logical" aspect of these transactions. That is, " order ingredients" 
would be the process, data flow into the process would be "order details" 
and data flow out would be "invoice details" of the flour and/or ingredients 
orders.

 Finally , there can't be external entity to extenal entity data flows such 
as driver to customer unless there is a process or a file in the middle of 
the two EEs. Therefore, the process of "place order" would/could be taken by 
driver from customer, and then sent on to the system as "order details" and 
so on. But , with no room in the Context diagram for both customer and 
driver we have a problem in representing this version of events. All 
external entities and data flows from them to and from the system have to be 
identified at the Context diagram stage.

I use the same book as you for DFDs Kevin, and I tell my students there is 
more than one correct answer as long as it can be justified from the story 
given.

In all humility and respect

Kevork Krozian
Edulists Creator and Administrator
www.edulists.com.au
kevork at edulists.com.au

----- Original Message ----- 
From: "Kevin Feely" <feely.kevin.k at edumail.vic.gov.au>
To: "Year 12 Software Development Teachers' Mailing List" 
<sofdev at edulists.com.au>
Sent: Friday, November 16, 2007 1:12 PM
Subject: Re: [Year 12 SofDev] Exam discussion - Edited

> Hi Kevork,
> i wish to humbly and with the deepest respect hold a different point of 
> view
> i agree a DFD must strictly adhere to the principle of concerning itself 
> with DATA and not any physical transactions, eg the bread, flour etc
> In this case study the drivers pass the orders into the system and receive 
> the invoices.
> The transaction between the drivers and customers is another transaction 
> entirely -and so is concerned with a different "system". IE that system 
> would concern itself with errors, efficiency, etc between customers and 
> drivers.
> If you wish to have a customer in this system as an entity i would only 
> mark you correct if you stated that the drivers were part of the system, 
> that is inside the bubble that is the flip flop bakery "system". If you 
> have assumed they are then i could agree with a customer as an entity. but 
> i think (that is me myself i) upon looking at this would have "sebastian" 
> as the system and look at the DATA coming to and from him.
> kev
>
>
>
> Kevork Krozian wrote:
>> Hi Kevin,
>>
>>  I would expect ( IMHO ) that the missing entity has to be customers.
>> The drivers' role is really one of a physical one. The fact they
>> collect data and deliver it, deliver invoices, and deliver products is a
>> physical consideration and not a logical one. How the data comes in or
>> is sent out is a physical consideration good for a system flowchart but
>> not a context diagram or DFD.
>> To extend the argument, the orders data could be collected via a
>> portable device connecting to a web server or even online by customers
>> by logging on to the same web site for orders. They could also print off
>> receipts when they order.
>>
>> Hope that helps .
>> See you all on Monday .... or Tuesday  .... or Wednesday at the famous
>> race course for the conference.....!
>>
>> Take Care
>>
>>
>> Kevork Krozian
>> IT Manager , Forest Hill College
>> k.krozian at fhc.vic.edu.au
>> http://www.fhc.vic.edu.au
>> Mobile: 0419 356 034
>>
>>
>>>>> Kevin Feely <feely.kevin.k at edumail.vic.gov.au> 16/11/2007 9:51 am
>>>>>
>>>>>
>> Hi Everyone,
>> I have added in my response to Adrian's kick off - see below
>> regards
>> kev
>>
>> Adrian Janson wrote:
>>
>>> Hi everyone,
>>>
>>> A couple of comments:
>>>
>>> Section C, Q1.
>>>
>>> I know that there are *reasons* why the Bakers have been included
>>>
>> as
>>> an entity (which I don*t agree with * BTW). However, in talking
>>>
>> to my
>>> students, this has created some confusion regarding what the missing
>>>
>>
>>
>>> entity should be. Many of my students felt that *Customers* would
>>>
>> have
>>> been the correct answer under other circumstances, however, as *Drivers* 
>>> were also described in the case study as providing data
>>>
>> to
>>> the system (in a similar way to the Bakers), they felt that
>>>
>> *Drivers*
>>> was correct. What do others think about this?
>>>
>>>
>> Iam happy with Bakers as an entity - it can be justified, if I had to 
>> mark a student who had put them in as part of the system Iam sure they
>>
>> could argue that successfully.
>> I would have put drivers as the missing entity. they interact with the
>>
>> system. Customers interact with the drivers so for customers to be 
>> correct you would have to indicate that the drivers were inside the 
>> "system" - unfortunately there is no space in the answer to show what you 
>> regard as part of the system
>> BUT IMHO since the bakers were an entity it is not logical that then
>> the drivers would be. By putting bakers as an entity you can draw the 
>> conclusion that sebastian is "the system"
>>
>>
>>> Q3b.
>>>
>>> Using the 2D array was a good inclusion which I applaud, however, the
>>>
>>
>>
>>> question is incorrect * and has the indexes the wrong way around! Kayla 
>>> has decided to test 1 bread product and 3 ingredients * but
>>>
>> in
>>> the test data the array indexes are (1,1), (2,1) and (3,1) *
>>>
>> instead
>>> of (1,1), (1,2) and (1,3).
>>>
>>>
>>
>> Does it not just depend on how you define your rows and columns? Yes 
>> yours is more logical, but i can work with the way it is on the exam
>>
>>
>>> Cheers,
>>>
>>> Adrian
>>>
>>>
>>
>> cheers kev
>> a teacher
>>
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>>>
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