Re: Equivalence of hierarchical and flat data formats

Consider the case where two of your books have multiple authors, in
different orders.

Peter Hunsberger


On Thu, Jul 28, 2022 at 6:09 AM Roger L Costello <[email protected]> wrote:

> Michael Kay wrote:
>
>
>
>    - it's very easy to do a mapping that supports all the same retrieval
>    queries, but doing a mapping that supports exactly the same set of
>    permitted updates is well nigh impossible.
>    - One of the issues here is ordering. As soon as you start
>    representing relationships using primary and foreign keys, you lose any
>    natural way of representing order in the relationship
>
>
>
> I don’t understand. The following flat data format uses primary/foreign
> keys to implement nesting:
>
>
>
> *BookList.dat*
> Compilers Principles, Techniques, Tools               AUT01
> Addison-Wesley               1986
> Introduction to Compiling Techniques               AUT02  McGraw-Hill
> 1996
> Economic Facts and Fallacies      AUT03               Basic Books
> 2011
> Economics in One Lesson             AUT04               Harper &
> Brothers           1946
>
> *AuthorsList.dat*
> AUT01   Alfred V. Aho, Ravi Sethi, Jeffrey Ullman
> AUT02   J. P. Bennett
> AUT03   Thomas Sowell
> AUT04   Henry Hazlitt
>
>
>
> Suppose I want to update the list of authors. Specifically, I want to add
> “John Doe” to the beginning of the AUT01 author list:
>
>
>
> AUT01   John Doe, Alfred V. Aho, Ravi Sethi, Jeffrey Ullman
>
>
>
> That update operation seems pretty straightforward to me. What is the
> issue that I’m not seeing?
>
>
>
> /Roger
>
>
>