Hi all<br><br>It seems from the sample exam's ERD that we don't need to indicate cardinality (1:1, 1:many etc) in our ERDs. If the exam decides to change its mind about this and shows cardinality, that would be a - umphh - cardinal sin. <rimshot><br>
<br>But seriously folks, without indications of cardinality, how can we get our money's worth from an ERD. Can one teacher supervise more than one class, or can a subject be supervised by more than one teacher? Can a student belong to more than one class? Can a class have many students?<br>
<br>One question: the sample ERD uses differences in shading as information (e.g. of key fields). Is this conventional? I pity students if they ever need to draw an entity with white text on black background in the exam.<br>
<br clear="all">And a dumb question: in which direction should the relationship between entities be read? Logically, the teacher gives the mark to the student. But read the other way, students give a mark to teachers. Are relationships commutative? <br>
<br>So many ERDs, so little red wine.<br><br>-- <br>Mark Kelly<br>Manager of ICT, Reporting, IT Learning Area<br>McKinnon Secondary College<br>McKinnon Rd McKinnon 3204, Victoria, Australia<br>Direct line / Voicemail: +613 8520 9085, Fax +613 9578 9253<br>
<a href="mailto:kel@mckinnonsc.vic.edu.au" target="_blank">kel@mckinnonsc.vic.edu.au</a><br>VCE IT Lecture Notes: <a href="http://vceit.com" target="_blank">http://vceit.com</a><br>Moderator: IT Applications Edulist<br><br>
<font>All generalisations are false, except this one.</font><br><br>