Re: Generic Modeling

In message <a23d3e$8a9$1_at_news.tue.nl>, Reinier Post <rp_at_win.tue.nl> writes
>Bernard Peek <bap_at_shrdlu.com> wrote:
>
>>It's trivially easy to store generic data in relational form, just
>>create table with three columns; Object, Property and Value.
>
>In general, it's not trivial to manipulate these data with SQL.

In a way. The difficulty is that the structure of the data isn't coded in the structure of the data, it's coded in the data itself. The database holds both data and metadata. That's difficult to handle if you aren't familiar with this sort of system and it gets progressively more difficult when the amount of metadata increases.

There have been a few times when I've incorporated this sort of structure in a database, invariably it's an unfinished development system. It's useful for gathering information about metadata. The users can define the properties that they want the system to record, which can then be incorporated into the finished system.

-- 
Bernard Peek
bap_at_shrdlu.com

In search of cognoscenti