Re: Academic name for associative array when used to pair column names with data

On Wednesday, March 19, 2014 3:47:26 AM UTC+1, william.d..._at_gmail.com wrote:
> I read Chris Date's book "An Introduction to Database Systems" where he uses the term "tuple" to describe what is commonly called a "row" in a database. What would the proper term be for an associative array of the column names paired with the data from a particular row (otherwise known as a hash)?
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> For example in Perl:
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> my _at_column_names = qw/color season sound/;
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> my _at_data = (
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> [ qw/blue fall loud/ ],
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> [ qw/red spring soft/ ],
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> [ qw/orange winter pin_drop/ ],
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> );
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> foreach my $tuple ( _at_data ) {
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> my %name_needed
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> = map { $column_names[$_] => $tuple->[$_] } 0 .. $#column_names;
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> }
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> What would be the proper name for the variable %name_needed? By proper name, I mean something along the lines of "tuple" rather than "hash" or "associative array" .
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> Is there a formal name for an associative array when it specifically contains a pairing of column names with data?
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> Mathematically it would look something like:
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> column_names: { a, b, c, d, e }
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> data:
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> {
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> { 1x1, 1x2, 1x3, 1x4, 1x5 },
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> { 2x1, 2x2, 2x3, 2x4, 2x5 },
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> { 3x1, 3x2, 3x3, 3x4, 3x5 },
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> { 4x1, 4x2, 4x3, 4x4, 4x5 },
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> { 5x1, 5x2, 5x3, 5x4, 5x5 }
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> }
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> Specifically, what would you call a given pairing of the column names with a tuple from the data, e.g.
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> { { a, 2x1 }, { b, 2x2 }, { c, 2x3 }, { d, 2x4 }, { e, 2x5 } }
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> Thanks ;-)

The thing that you describe here _IS_ the tuple as contained in the relation.

But for one detail perhaps : the {a, 2x1} things cannot be denoted as sets, their components must be ordered (otherwise you don't know which is the name and which is the value). Incidentally, this means that those (a, 2x1) things are themselves tuples too, at least mathematically speaking, however for the obvious reason of avoiding confusion, in RM contexts specifically they are typically not so labeled, but -usually- "attribute value" instead. Received on Wed Mar 19 2014 - 08:46:10 CET