I don't think an array of hashes and a hash of arrays could perfectly
represent a Table type.
There are several important facts of a relational model:unordered
columns and tupples, various constraints on columns. E.g. how can we
represent multi-unique constraints as an array of hashes?

On 4/4/09, Timothy S. Nelson <wayl...@wayland.id.au> wrote:
> On Sat, 4 Apr 2009, Xiao Yafeng wrote:
>>>> 3. Could I define primary key for a bag variable?
>>> All items in a Bag are "primary keys", but there's no data additional
>>> data associated with it.
>>     I mean whether I can see Set as a table  and Bag as a table with a
>> unique constraint? like:
>>        subset test of Bag(test_name Str, test_ID Int, primary
>> key(test_ID))
>       I don't think you can really do something like that.  Perl 6 as
> specified leaves many things up to libraries.  Implementing a Table type
> will
> no doubt be one of those things.  I would like to have a Table type that
> will
> work well with the Tree/Plex type that I am working on.
>       In the meantime, a table would need to be represented as an array of
> hashes, or a hash of arrays.
>       HTH,
> ---------------------------------------------------------------------
> | Name: Tim Nelson                 | Because the Creator is,        |
> | E-mail: wayl...@wayland.id.au    | I am                           |
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