[Year 12 SofDev] DFD question

Thu Sep 18 12:15:54 EST 2008

Hi Folks,

 A data dictionary can contain the following :
  1. a data element ( think of a field in a data table )
  2. a data flow as in a data flow diagram
  3. a data store ( think of a file )
  4. a process  ( the round things in DFDs )

  Whilst a data dictionary may be presented that contains only one part of a system ( fields in a table ) , it is not the only type of information found in a data dictionary.
A data dictionary has to be a system development/design tool so how can it only refer to fields in a table? Data in a system is not just a field in a table. 
In addition, a data dictionary needs to be able to be referred to at any stage of the SDLC, not just when database table design takes place.

A number of references refer to this explanation including Fitzpatrick , Keane ( the Thomson book referred to by Rob Mercer  - p 73 , not p25 ) and
  1. Systems Development Analysis, Feasiblity and Implementation by Olekalns ISBN 0=86458-040-1
  2. Systems Development Models by Courtier ISBN 1-875886-50-8
  3. System Documentaion Methods by Judy Adams 
  4. Management Information Systems - concepts, issues, tools and Applications by Tatnall, Davey,Burgess, and Davison ( Data Publishing )1998

  One problem has been that VCAA exams have referred to data dictionaries when describing database table design which is strictly correct. However, data dictionaries are not restricted to this type of use only and as that question in the 2007 exam illustrates, it is important for the students to understand this scope of use of data dictionaries.

 Hope that helps

Best Wishes

Kevork Krozian
IT Manager , Forest Hill College
k.krozian at fhc.vic.edu.au
http://www.fhc.vic.edu.au
Mobile: 0419 356 034

>>> Mark Kelly <kel at mckinnonsc.vic.edu.au> 18/09/2008 12:24 pm >>>
Did you mean page 73, or am I using the wrong book?

It's interesting how they explicitly include processes in a data 
dictionary (page 72) - I never have.

I see a data dictionary as a pure and simple table of field names, field 
types, lengths, validation rules perhaps.  Not processes, however: 
that's more for an N-S chart, for example.

Interesting though... might do a bit of digging around in the 'real' IT 
world and see what the conventions are there.

Then again, I really don't like their version of IPO charts on p74.  I 
like IPO to be pure "data / processing / information produced" e.g.

INPUT = Date of birth, Today's date
PROCESSING = (Today-DOB)/365.25
OUTPUT = Age

I really dislike using IPO charts as a uselessly vague version of a 
flowchart e.g. (from page 74)

INPUT = Personal details
PROCESSING = Check details
OUTPUT = Checked details

How pointless is that?

yuk.

Robert Mercer wrote:
> Hello,
> 
> I am looking at the data dictionary on page 25 of the Thomson SD text book and there appears to be process listed "Add New Member". I was of the understanding processes do not get listed in data dictionaries as is indicated by the 2007 exam Section C Question 2 c. Anyone have any thoughts?
> 
> Regards,
>  
> Rob Mercer
> ICT Outreach - Project Officer
> Faculty of Information & Communication Technologies
> Swinburne University of Technology
> PO Box 218
> Hawthorn VIC 3122 Australia
>  
> PH:  +61 3 9214 8768
> FAX :+61 3 9819 0823
> rmercer at swin.edu.au 
> 
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Mark Kelly
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McKinnon Secondary College
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