[Year 12 SofDev] DFDs

Mon Feb 25 11:29:37 EST 2013

I am with James on this with the DFD Entity question (and I did them at Uni too).
The system does not know or care what an entity is called as long as the data comes in from it - your label will not matter but you cannot have both entities as only one provides the data. "Order Entry Entity" - lol.
The data flow arrows labels do really matter as they represent the data.
David Dawson

From: sofdev-bounces at edulists.com.au [mailto:sofdev-bounces at edulists.com.au] On Behalf Of Vella, James
Sent: Monday, 25 February 2013 10:56 AM
To: sofdev at edulists.com.au
Subject: Re: [Year 12 SofDev] DFDs

Strictly speaking as someone who did DFDs at uni...

As Mark has said, we sometimes think in a human sense however DFDs don't allow us to see the interactions between two EEs.

As Selina has said, the waiter is just the input method - so we can leave it out. I think our students sometimes find it hard at this stage where they have to decide what should and shouldn't be included in our DFDs.

In terms of the DFD, you could argue either way for one or the other....but NOT BOTH! :)

That being said, in the UCD you can list both as actors because they both have roles in the system.

I have a whole text book on this stuff from my 2nd year at LaTrobe which I'm using with my kids at the moment...DFDs, UCDs, UML the whole kit and caboodle!

Regards

Mr James Vella

MacKillop College

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Today's Topics:

   1. Re: DFD question (Kent Beveridge)

   2. Re: DFD question (Mark)

   3. Re: DFD question (Selina Dennis)

----------------------------------------------------------------------

Message: 1

Date: Sun, 24 Feb 2013 21:57:28 +0000

From: Kent Beveridge <kbeveridge at stbc.vic.edu.au<mailto:kbeveridge at stbc.vic.edu.au>>

Subject: Re: [Year 12 SofDev] DFD question

To: "Year 12 Software Development Teachers' Mailing List"

                <sofdev at edulists.com.au<mailto:sofdev at edulists.com.au>>

Message-ID:

                <64FBC7D59E9D6B4DA547B82B7F07665C739FB287 at garlic.stbc.vic.edu.au<mailto:64FBC7D59E9D6B4DA547B82B7F07665C739FB287 at garlic.stbc.vic.edu.au>>

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Data flow to my understanding here..

Waiter to Customer ....Request for order

Customer to Waiter ....Food/Beverage order

Waiter and Customer both 'entities' send data back to the central part of the 'system' (restuarant system) via the waiter

Yep actors are waiter and customer.

I havent started UCD stuff with my guys just yet..focussing on DFD's ...ucd next.

Kent Beveridge

ICT Coordinator & Maths Teacher

kbeveridge at stbc.vic.edu.au<mailto:kbeveridge at stbc.vic.edu.au<mailto:kbeveridge at stbc.vic.edu.au%3cmailto:kbeveridge at stbc.vic.edu.au>>

________________________________

From: sofdev-bounces at edulists.com.au<mailto:sofdev-bounces at edulists.com.au> [sofdev-bounces at edulists.com.au] on behalf of Mark [mark at vceit.com]

Sent: Saturday, 23 February 2013 7:15 AM

To: Year 12 Software Development Teachers' Mailing List

Subject: Re: [Year 12 SofDev] DFD question

I had the same issue with the DFD and UCD for one of the programming outcomes.

The restaurant customer would be an obvious actor/external entity in a system that takes meal orders.

However since the waiter is the one interacting with the system, and the customer is interacting with the waiter, the customer does not appear at all in the system representation.

Sometimes what seems logical is not as it first appears.

On 22 February 2013 13:14, Simone Tynan <Simone.Tynan at shcy.vic.edu.au<mailto:Simone.Tynan at shcy.vic.edu.au<mailto:Simone.Tynan at shcy.vic.edu.au%3cmailto:Simone.Tynan at shcy.vic.edu.au>>> wrote:

Hi all,

I am having trouble with aspects of a DFD.

I have a DFD and context diagram in which shows a customer orders a service and it is quoted and carried out.

Similar scenario, except the service is being carried out for a beneficiary. (Think Ninja and assassins. ;-) )

The Customer is providing all details and payments. The beneficiary is not actually adding to or receiving from the system (that I can see).

Are they still added as an external entity? Is there any connection between them and the system?

Many thanks for any input/

Simone

************************************

Simone Tynan

eLearning Leader

LOTE Leader P-12

Simone.Tynan at shcy.vic.edu.au<mailto:Simone.Tynan at shcy.vic.edu.au<mailto:Simone.Tynan at shcy.vic.edu.au%3cmailto:Simone.Tynan at shcy.vic.edu.au>>

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Message: 2

Date: Mon, 25 Feb 2013 10:06:18 +1100

From: Mark <mark at vceit.com<mailto:mark at vceit.com>>

Subject: Re: [Year 12 SofDev] DFD question

To: "Year 12 Software Development Teachers' Mailing List"

                <sofdev at edulists.com.au<mailto:sofdev at edulists.com.au>>

Message-ID:

                <CACu=8Z0nWiAPpAFwtphqpdcGrduX+SbCYsErXimTjr9zZhX8OA at mail.gmail.com<mailto:CACu=8Z0nWiAPpAFwtphqpdcGrduX+SbCYsErXimTjr9zZhX8OA at mail.gmail.com>>

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Hi all. It's an interesting situation.  This is my take on it.

We all probably start by seeing it from a human point of view: the customer is dealing with the waiter, who deals with the system. So the customer is an integral part of the transaction and therefore appear in a DFD or UCD...

But the waiter is not a part of the system: he/she interacts with it as an external entity (EE).

So where does the customer fit in?  An EE to the EE waiter?  An EE once removed? We don't do that in DFD or UCD.

>From the system's point of view, the waiter is an EE. The customer is a

fictional character that the system does not see, hear, or believe in. Only the waiter exists to the system.  Everyone else is Santa Claus.

We could complicate it further and imagine that a child is giving her meal choice to her mother who gives it to the waiter... should the child be in the DFD/UCD now as an EE twice removed?

If a waiter were ordering his own lunch from the kitchen, would he be represented again in the diagram - this time as a customerless EE?

As I read it, the customer is not directly interacting with the system; the waiter is.  So the waiter appears as an EE.

So I would not include the customer at all in a DFD or UCD.

Anyone out there who did DFD/UCD at uni?

Cheers

Mark

On 25 February 2013 08:57, Kent Beveridge <kbeveridge at stbc.vic.edu.au<mailto:kbeveridge at stbc.vic.edu.au>>wrote:

>  Data flow to my understanding here..

>

> Waiter to Customer ....Request for order

>

> Customer to Waiter ....Food/Beverage order

>

> Waiter and Customer both 'entities' send data back to the central part

> of the 'system' (restuarant system) via the waiter

>

>

>

> Yep actors are waiter and customer.

>

>

>

> I havent started UCD stuff with my guys just yet..focussing on DFD's

> ...ucd next.

>

>

>  *Kent Beveridge*

> ICT Coordinator & Maths Teacher

> kbeveridge at stbc.vic.edu.au<mailto:kbeveridge at stbc.vic.edu.au>

>

>   ------------------------------

> *From:* sofdev-bounces at edulists.com.au<mailto:sofdev-bounces at edulists.com.au>

> [sofdev-bounces at edulists.com.au] on behalf of Mark [mark at vceit.com]

> *Sent:* Saturday, 23 February 2013 7:15 AM

> *To:* Year 12 Software Development Teachers' Mailing List

> *Subject:* Re: [Year 12 SofDev] DFD question

>

>   I had the same issue with the DFD and UCD for one of the programming

> outcomes.

> The restaurant customer would be an obvious actor/external entity in a

> system that takes meal orders.

> However since the waiter is the one interacting with the system, and

> the customer is interacting with the waiter, the customer does not

> appear at all in the system representation.

>

>  Sometimes what seems logical is not as it first appears.

>

>

> On 22 February 2013 13:14, Simone Tynan <Simone.Tynan at shcy.vic.edu.au<mailto:Simone.Tynan at shcy.vic.edu.au>>wrote:

>

>> Hi all,

>>

>>  I am having trouble with aspects of a DFD.

>>

>>  I have a DFD and context diagram in which shows a customer orders a

>> service and it is quoted and carried out.

>>

>>  Similar scenario, except the service is being carried out for a

>> beneficiary. (Think Ninja and assassins. ;-) )

>>

>>  The Customer is providing all details and payments. The beneficiary

>> is not actually adding to or receiving from the system (that I can see).

>>

>>  Are they still added as an external entity? Is there any connection

>> between them and the system?

>>

>>  Many thanks for any input/

>> Simone

>>

>> ************************************

>> Simone Tynan

>> eLearning Leader

>> LOTE Leader P-12

>> Simone.Tynan at shcy.vic.edu.au<mailto:Simone.Tynan at shcy.vic.edu.au>

>>

>>

>>    --

> --

> Mark Kelly

> mark AT vceit DOT com

> http://vceit.com

>

>

>     *St. Brigid's College *

>

> 97 Robinson Street, Horsham VIC 3400

>

> T 03 5382 3545   F 03 5382 0757

>

> ABN 72 749 438 155

>

> www.stbc.vic.edu.au<http://www.stbc.vic.edu.au>

>

>

--

--

Mark Kelly

mark AT vceit DOT com

http://vceit.com

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Message: 3

Date: Mon, 25 Feb 2013 10:30:44 +1100

From: "Selina Dennis" <selina at dennis.net.au<mailto:selina at dennis.net.au>>

Subject: Re: [Year 12 SofDev] DFD question

To: "'Year 12 Software Development Teachers' Mailing List'"

                <sofdev at edulists.com.au<mailto:sofdev at edulists.com.au>>

Message-ID: <002d01ce12e6$f902a040$eb07e0c0$@dennis.net.au<mailto:002d01ce12e6$f902a040$eb07e0c0$@dennis.net.au>>

Content-Type: text/plain; charset="us-ascii"

Hi Mark,

I'd disagree with your argument in regards to the Customer not playing a role in interacting with the system. To me, the waiter is simply the input method - much like a keyboard - and the information is coming from the customer. So in a DFD/UCD scenario, I wouldn't include the waiter in the process of ordering food - that would come from the customer. However, if the waiter had some other interaction with the system, such as collecting tips at the end of the day, then they would become more than simply the input method, and thus would be shown.

Hope that makes sense! Just my take on it.

Selina Dennis

Strathmore Secondary College

From: sofdev-bounces at edulists.com.au<mailto:sofdev-bounces at edulists.com.au> [mailto:sofdev-bounces at edulists.com.au]

On Behalf Of Mark

Sent: Monday, 25 February 2013 10:06 AM

To: Year 12 Software Development Teachers' Mailing List

Subject: Re: [Year 12 SofDev] DFD question

Hi all. It's an interesting situation.  This is my take on it.

We all probably start by seeing it from a human point of view: the customer is dealing with the waiter, who deals with the system. So the customer is an integral part of the transaction and therefore appear in a DFD or UCD...

But the waiter is not a part of the system: he/she interacts with it as an external entity (EE).

So where does the customer fit in?  An EE to the EE waiter?  An EE once removed? We don't do that in DFD or UCD.

>From the system's point of view, the waiter is an EE. The customer is a

fictional character that the system does not see, hear, or believe in. Only the waiter exists to the system.  Everyone else is Santa Claus.

We could complicate it further and imagine that a child is giving her meal choice to her mother who gives it to the waiter... should the child be in the DFD/UCD now as an EE twice removed?

If a waiter were ordering his own lunch from the kitchen, would he be represented again in the diagram - this time as a customerless EE?

As I read it, the customer is not directly interacting with the system; the waiter is.  So the waiter appears as an EE.

So I would not include the customer at all in a DFD or UCD.

Anyone out there who did DFD/UCD at uni?

Cheers

Mark

On 25 February 2013 08:57, Kent Beveridge <kbeveridge at stbc.vic.edu.au<mailto:kbeveridge at stbc.vic.edu.au>>

wrote:

Data flow to my understanding here..

Waiter to Customer ....Request for order

Customer to Waiter ....Food/Beverage order

Waiter and Customer both 'entities' send data back to the central part of the 'system' (restuarant system) via the waiter

Yep actors are waiter and customer.

I havent started UCD stuff with my guys just yet..focussing on DFD's ...ucd next.

Kent Beveridge

ICT Coordinator & Maths Teacher

kbeveridge at stbc.vic.edu.au<mailto:kbeveridge at stbc.vic.edu.au>

  _____

From: sofdev-bounces at edulists.com.au<mailto:sofdev-bounces at edulists.com.au> [sofdev-bounces at edulists.com.au] on behalf of Mark [mark at vceit.com]

Sent: Saturday, 23 February 2013 7:15 AM

To: Year 12 Software Development Teachers' Mailing List

Subject: Re: [Year 12 SofDev] DFD question

I had the same issue with the DFD and UCD for one of the programming outcomes.

The restaurant customer would be an obvious actor/external entity in a system that takes meal orders.

However since the waiter is the one interacting with the system, and the customer is interacting with the waiter, the customer does not appear at all in the system representation.

Sometimes what seems logical is not as it first appears.

On 22 February 2013 13:14, Simone Tynan <Simone.Tynan at shcy.vic.edu.au<mailto:Simone.Tynan at shcy.vic.edu.au>>

wrote:

Hi all,

I am having trouble with aspects of a DFD.

I have a DFD and context diagram in which shows a customer orders a service and it is quoted and carried out.

Similar scenario, except the service is being carried out for a beneficiary.

(Think Ninja and assassins. ;-) )

The Customer is providing all details and payments. The beneficiary is not actually adding to or receiving from the system (that I can see).

Are they still added as an external entity? Is there any connection between them and the system?

Many thanks for any input/

Simone

************************************

Simone Tynan

eLearning Leader

LOTE Leader P-12

Simone.Tynan at shcy.vic.edu.au<mailto:Simone.Tynan at shcy.vic.edu.au>

--

--

Mark Kelly

mark AT vceit DOT com

http://vceit.com

St. Brigid's College

97 Robinson Street, Horsham VIC 3400

T 03 5382 3545   F 03 5382 0757

ABN 72 749 438 155

www.stbc.vic.edu.au<http://www.stbc.vic.edu.au> <http://www.stbc.vic.edu.au/>

--

--

Mark Kelly

mark AT vceit DOT com

http://vceit.com

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