[Year 12 SofDev] SD Exam - Question 4

[Laurie Savage]

That's how my students read it and I agree.

 

Laurie

 

From: sofdev-bounces at edulists.com.au [mailto:sofdev-bounces at edulists.com.au]
On Behalf Of Andrew Shortell
Sent: Wednesday, 17 November 2010 1:45 PM
To: Year 12 Software Development Teachers' Mailing List
Subject: Re: [Year 12 SofDev] SD Exam - Question 4

 

Null  - if there is nothing then what is the point in proceeding further
Type - if there is other than numbers then no point in doing any other
checks
Length - no point in checking the database if there is incorrect number of
digits
Existence - checking the database is a significant step which goes outside
of the current program to an external source

I have not yet seen the exam.. It is not offered here but as a teacher of
IS/SoD for a few years and lectured to 3rd year programmers this is how I
would approach it.

Effectiveness in terms of why go to the next step when it has failed a
step...
It would be pretty silly to put it in the reverse order would n't it...
Check against the database before you even know if anything has been
entered? Etc

Andrew


-- 
Andrew Shortell 
(soon to leave Wallan SC)



On 17/11/10 1:10 PM, "Mark KELLY" <kel at mckinnonsc.vic.edu.au> wrote:

Hi all.  I've started getting a bee in my bonnet (or a terrier in my
trousers) about Section C, Q4.

Percy is writing the program specification. For the section dealing with
entry of the Medicare number he writes

If the user makes a mistake entering the Medicare number, the program has to
provide as much information as possible about what is wrong. Therefore
include these validation tests.
Length - to make sure that the correct number of characters has been entered
Existence - to make sure that the number entered exists on Medicare's
database
Null - to make sure something has been entered
Type - to make sure that only numeric characters have been entered
Note: These tests must be performed in the most effective order.

a. Place these validation tests in the most effective order. 1 mark

Then students have to give 3 reasons why it's the most effective way of
doing those tests. (3 marks)


Hmm. What is "effective" about the order? It must relate to how well it does
the job of finding invalid numbers.

But if all 4 tests are going to be conducted, any order of the 4 tests will
yield exactly the same results.

It might be different if we wanted to find invalid numbers soonest, or with
the minimum number of tests, but they are efficiency criteria, not
effectiveness.

I'm seriously starting to believe that this is a Bull Mastiff of a
question... All orders must be equally effective.

I can usually work out what the examiners were probably trying to get at,
but this one has me completely baffled (like multichoice Q3 on the ITA
paper).  
I have no idea whatsoever of what knowledge the examiners are hoping I will
show.

So, can anyone please tell me:

1. how one order can be more effective than another.
2. what order is most effective, and why the reverse order would be less
effective!

Growl.

Mark


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