[Informatics] ERD policy

[Garth, Lucas A]

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] 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

[Description: Marcellin_College_Logo_RGB_HR]

Marcellin College
160 Bulleen Road
Bulleen VIC 3105 Australia

T +61 3 9851 1698
ABN 77 413 001 496

marcellin.vic.edu.au<http://www.marcellin.vic.edu.au/>
twitter.com/Marcellin<http://twitter.com/MCBulleen>

From: 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

Natalie Heath
Marcellin Staff
[Marcellin College Logo]
MARCELLIN COLLEGE
160 Bulleen Road
Bulleen VIC 3105 Australia
T +61 3 9851 1698
F +61 3 9851 1555
ABN 77 413 001 496
marcellin.vic.edu.au<http://marcellin.vic.edu.au>
twitter.com/Marcellin<http://twitter.com/Marcellin>
DISCLAIMER: This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error, please notify the sender immediately by reply email and delete the email from your system. Please note that any views or opinions presented in this email are solely those of the author and do not necessarily represent those of Marcellin College. Marcellin College does not guarantee that this email is virus or error free and accepts no liability for any damage caused by any virus transmitted by this email.

Important - This email and any attachments may be confidential. If received in error, please contact us and delete all copies. Before opening or using attachments check them for viruses and defects. Regardless of any loss, damage or consequence, whether caused by the negligence of the sender or not, resulting directly or indirectly from the use of any attached files our liability is limited to resupplying any affected attachments. Any representations or opinions expressed are those of the individual sender, and not necessarily those of the Department of Education and Training.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.edulists.com.au/pipermail/informatics/attachments/20160418/36707270/attachment-0001.html 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.jpg
Type: image/jpeg
Size: 3933 bytes
Desc: image001.jpg
Url : http://www.edulists.com.au/pipermail/informatics/attachments/20160418/36707270/image001-0001.jpg