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Mike Champion scripsit:
> The key differentiator was that CODASYL ultimately
> relied on "pointers" (which I'm pretty sure are functionally much like
> hyperlinks, at least by analogy) to relate bits of information that did
> not fit into a hierarchy,
Actually, the CODASYL model was about multi-hierarchies, with none
preferred. Here's how you'd do the CODASYL model on a relational DBMS,
which is historically backward, but a lot more people understand RDBMSes.
Data is kept in objects like relational tables, except that the primary
key is always a generated unique ID. (Implementationally, this was
an address.)
Then there would be linkage tables, potentially one per pair of tables,
with the fields <primary key 1>, <primary key 2>, <sort order>. (This was
implemented as a linked list of primary-key-2s starting from the record
labeled by primary-key-1.) All navigation must be done through these links.
--
What is the sound of Perl? Is it not the John Cowan
sound of a [Ww]all that people have stopped jcowan@reutershealth.com
banging their head against? --Larry http://www.ccil.org/~cowan
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