[Year 12 SofDev] SD Exam - Question 4

[Neil Wallace]

Hi Mark.

 

I agree with what you are saying, but they may be looking for something
along the lines of running the null then  type checks first to allow
skipping the others if there is no length or existence to check. The
efficiency angle is all I see.

 

Lame, but about the only thing I can think of. (And I have to dash to a late
extra)

 

Neil Wallace

Norwood Secondary College

 

From: sofdev-bounces at edulists.com.au [mailto:sofdev-bounces at edulists.com.au]
On Behalf Of Mark KELLY
Sent: Wednesday, 17 November 2010 1:11 PM
To: Year 12 Software Development Teachers' Mailing List
Subject: [Year 12 SofDev] SD Exam - Question 4

 

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
Moderator: IT Applications Edulist

My cow died on this day two years ago.  I know because I noted it in my
dairy.



-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.edulists.com.au/pipermail/sofdev/attachments/20101117/e4ebfd7c/attachment-0001.html