[Year 12 SofDev] Oliver's Mexican Cantina

Fri Jul 29 15:07:16 EST 2011

The study design example was doing its best to curtail the scope of the
student's software: a wise and noble ambition. 
I can appreciate why the example wanted to exclude the need for complex
wireless data transmission from the student's scope, but the unrealistic
repercussions in the CD/DFD (as you described) don't sit well either.

>>>>> Agreed, but I would still point out that a CD / DFD is not concerned
about how the data is transmitted, whether by wireless or donkey, so this
should not have ever been a part of the solution at this level.

I don't know what the official definition of a data store is, or even if
there is one at all.

>>>>> Unfortunately there is no agreed convention on what a data store is,
no. Same as what shape a data store should be, etc.

If a program writes data to a file, but never reads it back again, is it
still a data store?  

>>>> Yes it is, although it would be a very poorly designed system, because
the data in the store would be essentially worthless.

It's a handkerchief dropped by the roadside waiting for the other software
to come along and pick it up.
Most of the time our DFD data stores are read/write. 

>>>>> As they should.

This rare exception in the Cantina example is unusual and (I find) hard to
handle using basic DFD/CD theory because it is so unusual.

>>>> I agree. Cantina needs Gordon Ramsay to go in and give em a real shake
up.

>>>>>I'll see your 4 Mauritanian ouguiyas and 2 khoums'  and raise it 2
albanian lek and 60 qindarka.

Allan.

Anyway, that's my 4 Mauritanian ouguiyas and 2 khoums' worth.

On 29 July 2011 09:58, Allan Barnes <abarnes at aiet.com.au> wrote:

Hi Mark

I have to admit I didn't spend a lot of time reading the case study in the
study design, although I did find it a little confusing. I don't quite
understand the idea behind the kitchen system - if I was designing the info
system (which clearly I'm not) the external entity at the end of the line
would be the chef who stands there and yells out the orders  a la Gordon
Ramsey but without the swearing, and the kitchen system would therefore just
be the display mechanism for the order to be received, similar to a printer,
for example. The transmitting software I also would not have considered as
an entity either as it is just the method used to transfer the data from the
waiter to the chef, and therefore is not part of the systems analysis model.

To me it is:

Error! Filename not specified.

As pointed out, if it is a context diagram the data store is not shown, but
if it is a DFD it is. I read the case study once and couldn't see any
reference to whether it needed to be a DFD or context diagram - it may have
been in there and I missed it.

The way I was taught at Uni was that the system analysis stage is not
interested in how the information gets from point A to point B - that is the
domain of the person designing the system, thus the hand-held PC, the
transmitting software and the display are irrelevant to the analysis of the
system. If Gordon says he wants his waiters to have hand held PC's and the
data to be transmitted somehow to somewhere and displayed on a screen then
this is part of my design of the system but is not relevant to how the
information is gathered and processed.

I don't know if systems analysis and design has changed since my uni days
but we were always taught a very strict delineation between analysis and
design and what was considered in each stage.

The Aussie dollar is doing well so I'm back on the Aussie (no disrespect to
the PNG currency).

Kind regards

Allan Barnes, CEO

Australian Institute of Education and Training

P.O. Box 171

Brunswick West 3055

Melbourne, Victoria

Ph: (03) 9387 2051

FAX: (03) 9387 3470

Mobile: 0409 428 221

From: sofdev-bounces at edulists.com.au [mailto:sofdev-bounces at edulists.com.au]
On Behalf Of Mark KELLY
Sent: Friday, 29 July 2011 9:32 AM

To: Year 12 Software Development Teachers' Mailing List

Subject: Re: [Year 12 SofDev] Oliver's Mexican Cantina

Hi Alan. The kitchen display, to my way of thinking, is not connected to the
Cantina software at all (a conscious decision by the author to limit the
scope of the mobile device's functional requirements.) 

Between the mobile software and the kitchen system (which is an external
entity) lies the transmitting software (also an external entity), and you
don't show communications between external entities.

2 pigs and 1 yam's worth (for our Papua New Guinean readers)

Regards
Mark

On 28 July 2011 14:03, Allan Barnes <abarnes at aiet.com.au> wrote:

Hi Mark

To my thinking the second terminator is the kitchen display and not the
software itself. This is because (IMHO) the software is the method of
transmitting the text file containing the order whereas the kitchen display
is if you like the end user. Happy to be shot down in flames though. My 1c
worth.

Error! Filename not specified.

Kind regards

Allan Barnes, CEO

Australian Institute of Education and Training

P.O. Box 171

Brunswick West 3055

Melbourne, Victoria

Ph: (03) 9387 2051

FAX: (03) 9387 3470

Mobile: 0409 428 221

From: sofdev-bounces at edulists.com.au [mailto:sofdev-bounces at edulists.com.au]
On Behalf Of Mark KELLY
Sent: Thursday, 28 July 2011 1:43 PM
To: Year 12 Software Development Teachers' Mailing List
Subject: [Year 12 SofDev] Oliver's Mexican Cantina

Hi all. I'm playing with an SRS based on the Cantina (study design p.84).

I've got to the context diagram, and I've attached a first draft.  I'm not
100% of a couple of things:

1. I have excluded the customers as an external entity since they don't
interact with the system: the waiter does.

2. I included the transmission software as an external entity since it takes
the text file from the ordering software.  But if the text file is saved
should it then be considered outside of the system rather than an active
data store within the system?  In that case, the transmission software
should not be included at all.

Any ideas?

Cheers
Mark

-- 
Mark Kelly
Manager of ICT, Reporting, IT Learning Area
McKinnon Secondary College
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McKinnon Secondary College
McKinnon Rd McKinnon 3204, Victoria, Australia
Direct line / Voicemail: +613 8520 9085, Fax +613 9578 9253
kel at mckinnonsc.vic.edu.au
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-- 
Mark Kelly
Manager of ICT, Reporting, IT Learning Area
McKinnon Secondary College
McKinnon Rd McKinnon 3204, Victoria, Australia
Direct line / Voicemail: +613 8520 9085, Fax +613 9578 9253
kel at mckinnonsc.vic.edu.au
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