[Informatics] ERD policy

Sat Apr 23 14:44:48 AEST 2016

Thanks Roger

I use this as an introduction .. the background noise is irritating but I like how she rattles it off 
https://www.evernote.com/l/AB_doASLxRlIZInCq6VIDRhUpfeOR0pAOoo <https://www.evernote.com/l/AB_doASLxRlIZInCq6VIDRhUpfeOR0pAOoo>

An opening handout that I issue
https://www.evernote.com/l/AB9sWC2XUGlDv4iFp6vMlBQ85r6FzAHRB9M <https://www.evernote.com/l/AB9sWC2XUGlDv4iFp6vMlBQ85r6FzAHRB9M>

And another that I adapted ..
https://www.evernote.com/l/AB9Kgf8CrE1EBIGvWU7yOYDrvq4mQ_h1UeU <https://www.evernote.com/l/AB9Kgf8CrE1EBIGvWU7yOYDrvq4mQ_h1UeU>

Hope that some find this helpful

Regards Roland

> On 18 Apr 2016, at 2:16 PM, Roger SIDHOM <rsidhom at ozford.edu.au <mailto:rsidhom at ozford.edu.au>> wrote:
> 
> I found this short Youtube video really helped!
>  
> https://www.youtube.com/watch?v=c0_9Y8QAstg <https://www.youtube.com/watch?v=c0_9Y8QAstg>
>  
> Roger Sidhom
>  
> From: ATKINSON-BUCK, Damien [mailto:Damien.ATKINSON-BUCK at ivanhoe.com.au <mailto:Damien.ATKINSON-BUCK at ivanhoe.com.au>] 
> Sent: Monday, 18 April 2016 12:36 PM
> To: Year 12 VCE Informatics Teachers' Mailing List
> Subject: Re: [Informatics] ERD policy
>  
> Hi Lucas, <>
> I think the N is a reference to the N used in mathematics when looking at the cardinality of sets of numbershttps://en.wikipedia.org/wiki/Cardinal_number <https://en.wikipedia.org/wiki/Cardinal_number> and https://en.wikipedia.org/wiki/Aleph_number <https://en.wikipedia.org/wiki/Aleph_number>
> Not sure when databases started using M as an additional letter to represent many, except to suggest that maybe it is was to avoid confusion of both tables requiring the same number of records by having the same letter linked to it?
> Cheers
> Damien
>  
>  
> Damien Atkinson-Buck  
> Head of Learning Area: Technology/Arts 
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> From: Garth, Lucas A [mailto:garth.lucas.a at edumail.vic.gov.au <mailto:garth.lucas.a at edumail.vic.gov.au>] 
> Sent: Monday, 18 April 2016 12:07 PM
> To: Year 12 VCE Informatics Teachers' Mailing List
> Subject: Re: [Informatics] ERD policy
>  
> Hi Natalie & Mark
>  
> Seems no one knows what is going on. I’ve drummed into my students that one to many is 1:N despite how illogical it looks.
>  
> I’d have been fine for one to many to be 1:M and many to many to have M:M or even M:N.  But the research books I’ve seen use 1:N.
>  
> I imagine N stands for “a number of records” rather than many records.  (Then why don’t we use N:N?)
>  
> In the end all we want is consistency and I’m not sure the document provides this.  Page 3 needs to change the top diagram to be 1:M to ensure all of the diagrams are consistent.
>  
> Maybe it’s best to just always use crows feet and be done with it.
>  
> Lucas
>  
>  
> From: informatics-bounces at edulists.com.au <mailto:informatics-bounces at edulists.com.au> [mailto:informatics-bounces at edulists.com.au <mailto:informatics-bounces at edulists.com.au>] On Behalf Of Heath, Natalie
> Sent: Monday, 18 April 2016 11:35 AM
> To: Year 12 VCE Informatics Teachers' Mailing List
> Subject: Re: [Informatics] ERD policy
>  
> Thanks Mark. I wish I’d had this when I was actually teaching it…. Last term….
>  
> Quick question. On page 3 the sample has 1:N library member borrows book…. Shouldn’t this be 1:M? Or am I missing something? 1:N isn’t in the list above it so I’m nicely confused.
>  
> Natalie
>  
> Mrs Natalie Heath
> ICT Learning Coordinator
>  
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> Marcellin College
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> From: informatics-bounces at edulists.com.au <mailto:informatics-bounces at edulists.com.au> [mailto:informatics-bounces at edulists.com.au <mailto:informatics-bounces at edulists.com.au>] On Behalf Of Mark
> Sent: Monday, 18 April 2016 11:12 AM
> To: Year 12 VCE Informatics Teachers' Mailing List
> Subject: [Informatics] ERD policy
>  
> Hi folks. The long-awaited VCAA Entity Relationship Diagram policy <http://www.vcaa.vic.edu.au/Documents/vce/computing/Informatics_examination_ER_Conventions.docx> is out.
>  
> And it includes cardinality with both Chen "1/M/N" and crowsfeet notations!
>  
> Finally!
>  
> -- 
>  
> Mark Kelly
>  
> mark at vceit.com <mailto:mark at vceit.com>
> http://vceit.com <http://vceit.com/>
>  
> Natalie Heath
> Marcellin Staff
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