Re:Migrating to Python 3 with pleasure
by empthought on Monday February 05, 2018 @10:59AM
(#16309571)
Order-significance is exactly how the relational model was defined in the beginning
"An array which represents an n-ary relation R has the following properties:
1. Each row represents an n-tuple of R.
2. The ordering of rows is immaterial.
3. All rows are distinct.
4. The ordering of columns is significant -- it corresponds to the ordering S1, S2, ..., Sn of the domains on which R is defined (see, however, remarks below on domain-ordered and domain-unordered relations).
5. The significance of each column is partially conveyed by labeling it with the name of the corresponding domain."
-- A relational model of data for large shared data banks[1]
"An array which represents an n-ary relation R has the following properties:
1. Each row represents an n-tuple of R.
2. The ordering of rows is immaterial.
3. All rows are distinct.
4. The ordering of columns is significant -- it corresponds to the ordering S1, S2, ..., Sn of the domains on which R is defined (see, however, remarks below on domain-ordered and domain-unordered relations).
5. The significance of each column is partially conveyed by labeling it with the name of the corresponding domain."
-- A relational model of data for large shared data banks[1]
[1]: https://cs.uwaterloo.ca/~david/cs848s14/codd-relational.pdf