Re: Equivalence of hierarchical and flat data formats

> 
> I don’t understand. The following flat data format uses primary/foreign keys to implement nesting:

In relational database normalization, a one-to-many relationship like book-has-author is usually represented by adding a primary key to the "one" end (book) and a foreign key to the "many" end (author). The problem then is how to represent the fact that there is a defined ordering to the authors of a book; and there's a variety of ways of handling this.

You've completely ignored normalization here - which is your prerogative, but it makes it meaningless to talk about primary and foreign keys.

Actually of course the book-has-author relationship is many-to-many, which creates another raft of issues.


Michael Kay
Saxonica


>  
> 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