6th normal form
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6th normal form
Hi, i need help from someone who can explain what the 6th normal form is how it proceeds from the 5th normal form, as it is written in "temporal data and the relational model" by Hugh Darwen thanks
- Chris Corbyn
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School/University question? 
http://www.tonymarston.co.uk/php-mysql/ ... n.html#6nf
http://www.tonymarston.co.uk/php-mysql/ ... n.html#6nf
6th (Domain-Key) Normal Form
A table is in sixth normal form (6NF) or Domain-Key normal form (DKNF) if it is in 5NF and if all constraints and dependencies that should hold on the relation can be enforced simply by enforcing the domain constraints and the key constraints specified on the relation.
Another way of expressing this is:
... if every constraint on the table is a logical consequence of the definition of keys and domains.
1. An domain constraint (better called an attribute constraint) is simply a constraint to the effect a given attribute A of R takes its values from some given domain D.
2. A key constraint is simply a constraint to the effect that a given set A, B, ..., C of R constitutes a key for R.
- Chris Corbyn
- Breakbeat Nuttzer
- Posts: 13098
- Joined: Wed Mar 24, 2004 7:57 am
- Location: Melbourne, Australia
- Chris Corbyn
- Breakbeat Nuttzer
- Posts: 13098
- Joined: Wed Mar 24, 2004 7:57 am
- Location: Melbourne, Australia
The only implementation i've seen untill now looks as following:
- Each property (apart from the PK) is saved in it's property_table (PK, timestamp, value).
http://www.cs.man.ac.uk/img/TIME-2002/darwen-time02.pdf
- Each property (apart from the PK) is saved in it's property_table (PK, timestamp, value).
http://www.cs.man.ac.uk/img/TIME-2002/darwen-time02.pdf