[Year 12 SofDev] SD Exam - Question 4

[Mark KELLY]

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
-- 
Mark Kelly
Manager Information Systems
Reporting Manager
IT Learning Area Manager

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

VCE IT Lecture Notes: http://vceit.com
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