[Yr11 Information Technology] Data Flow Diagrams

[David Dawson]

Context -> Level 0 DFD -> ONE process, no datastore, several entities
Level 1 DFD -> 3 processes (approx) lacks detail -> has datastores
(this is the first expansion of the single process Context or level 0)
That is how I learnt it anyway.


David Dawson
Head of Information Technology Learning Area
Head of Learning Technologies
St Kilda Rd Campus
Wesley College 
577 St Kilda Rd
Melbourne 3004
Ph 8102 6340
Mob 0425 718147


>>> kel at mckinnonsc.vic.edu.au 09/04/08 2:52 pm >>>
Hi Litsa.

Yes, the lack of storage shapes definitely marks a CD.

I've seen the Context Diagram as a representation of the system as a 
single, featureless black box connected to its external entities. Hence 
the 'context'.

Once you open the black box and look inside, you start with DFDs.

Anyway, many sites say CD = DFD level zero.  There seem to be different 
opinions on the definitions...

Litsa Tzelepis wrote:
> hi mark,
> 
> i was going by the definitions in the book, but that's how i got taught 
> these diagrams at uni too - context diagrams are a representation of the 
> info. system without the inclusion of storage files, and the level 0 
> diagram is when the files are also drawn in and each process is 
> labelled, 1, 2, 3, etc. Level 1 diagrams are when the bubbles are broken 
> down further and labelled 1.1, 1.2, 1.3, etc. And so it goes..
> 
> sorry if i have confused anyone, litsa
> 
> 
> ----- Original Message ----- From: "Mark Kelly" <kel at mckinnonsc.vic.edu.au>
> To: "Year 11 Information Technology Teachers' Mailing List" 
> <yr11it at edulists.com.au>
> Sent: Thursday, September 04, 2008 12:20 PM
> Subject: Re: [Yr11 Information Technology] Data Flow Diagrams
> 
> 
>> I've always believed context diagrams WERE Level 0 DFDs...
>>
>> Googling seems to confirm it.
>>
>> Robert Minato wrote:
>>> Thanks for the reply Laurie and Litsa
>>>
>>> Don't have IT at work in our library but I like Litsa's idea of only 
>>> going to Level 0.
>>>
>>> Thanks for the suggestions
>>>
>>> Rob
>>>
>>> Robert Minato
>>> Technology Domain Leader
>>> Catholic College Wodonga
>>> 02 6043 5546
>>>
>>>
>>>
>>>
>>>
>>> On 03/09/2008, at 10:57 AM, Litsa Tzelepis wrote:
>>>
>>>> hello.
>>>> i also use potts, but i have the jacaranda text for the occassional 
>>>> backup.
>>>> if you have this text, try go to page 255 - 258. this should help.
>>>>  i teach context diagrams and then level 0 - i then discuss level 1, 
>>>> level 2, etc. but tell the students they only need to worry about 
>>>> the context diagram and level 0.
>>>>  hope this helps, litsa
>>>>
>>>>     ----- Original Message -----
>>>>     *From:* Robert Minato <mailto:rminato at ccw.vic.edu.au>
>>>>     *To:* Year 11 Information Technology Teachers' Mailing List
>>>>     <mailto:yr11it at edulists.com.au>
>>>>     *Sent:* Wednesday, September 03, 2008 7:57 AM
>>>>     *Subject:* [Yr11 Information Technology] Data Flow Diagrams
>>>>
>>>>     I'm preparing for DFDs, something I've not taught before. The
>>>>     Potts text give two pages of, too me, brief cover. When I look at
>>>>     the DFD examples on the VITTA support cd, I feel I'm way short of
>>>>     knowing much about them. Context/level 0 diagrams are fine, but
>>>>     going further seems to leave a lot of interpretation to the
>>>>     imagination. Given that my students aren't very worldly, I don't
>>>>     expect them to grasp the topic very easily.
>>>>
>>>>     How deep are we expected to cover DFDs? The study design
>>>>     lists: tools for representing data flows, including data fl ow 
>>>> diagrams.
>>>>
>>>>     Does anyone have any notes to better exp! lain level 1 and level 2?
>>>>
>>>>     Regards
>>>>
>>>>     Rob
>>>>
>>>>     Robert Minato
>>>>     Technology Domain Leader
>>>>     Catholic College Wodonga
>>>>     02 6043 5546
>>
>>
>> -- 
>> Mark Kelly
>> Manager - Information Systems
>> McKinnon Secondary College
>> McKinnon Rd McKinnon 3204, Victoria, Australia
>> Direct line / Voicemail: 8520 9085
>> School Phone +613 8520 9000
>> School Fax +613 95789253
>> kel AT mckinnonsc.vic.edu.au
>>
>> Webmaster - http://www.mckinnonsc.vic.edu.au 
>> IT Lecture notes: http://vceit.com 
>> Moderator: IT Applications Mailing List
>>
>> A conclusion is the place where you got sick of thinking.

> 


-- 
Mark Kelly
Manager - Information Systems
McKinnon Secondary College
McKinnon Rd McKinnon 3204, Victoria, Australia
Direct line / Voicemail: 8520 9085
School Phone +613 8520 9000
School Fax +613 95789253
kel AT mckinnonsc.vic.edu.au

Webmaster - http://www.mckinnonsc.vic.edu.au 
IT Lecture notes: http://vceit.com 
Moderator: IT Applications Mailing List

A conclusion is the place where you got sick of thinking.

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