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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: GNAT GPL is not shareware
Date: Fri, 9 Jan 2015 16:07:25 -0600
Organization: Jacob Sparre Andersen Research & Innovation
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Xref: news.eternal-september.org comp.lang.ada:24512
Date: 2015-01-09T16:07:25-06:00
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"Shark8" <OneWingedShark@gmail.com> wrote in message 
news:U%Xrw.246026$pr4.26650@fx26.iad...
> On 09-Jan-15 14:33, Randy Brukardt wrote:
>> I haven't any clue as to what you are talking about. Visiblity 
>> information
>> is tree-structured, and it is not possible to map trees sensibly into the
>> flat tables required by relational technology. Doing so distorts the 
>> problem
>> (as Dmitry notes).
>
> It actually is possible to store a tree structure in a "flat table" -- 
> see recursive queries. -- 
> http://en.wikipedia.org/wiki/Hierarchical_and_recursive_queries_in_SQL

Of course it's possible -- it's just unnatural. The reason Ada now has a 
tree container is directly because of that -- while you can map a tree into 
a flat structure, you have to do some sort of encoding to do so. It's better 
to directly have the structure.

(Now, if someone wanted to promulagate an "everything is a tree" strategy 
and algebra, I'd be interested, because there are very few problems that 
aren't a tree of some sort.)

                                    Randy.