Darren New wrote:

> Incidentally, for history buffs, that was one of the three or four 
> revolutionary amazing-at-the-time things that the relational model 
> introduced: the metadata of the data is accessible as data. That hit the 
> data world the way von Neumann architecture hit the electrical 
> engineering world. :-)
> 
> (The others being a mathematically rigorous foundation, a lack of 
> pointers, and separation of modeling concerns from efficiency concerns, 
> all of which were astoundingly revolutionary at the time.)

The way I heard it, before databases came along, if you had a dozen 
programs that all accessed the same pot of data, they all had to 
understand the same file format. And if you *changed* that file format, 
all your programs broke - usually be silently producing gibberish 
instead of real data. Then you'd have to go modify them all one by one 
to fix them.

Story goes that one company changed their file format so that some of 
their bills to customers contained gibberish which actually leaked 
information about their supplier relationships. A competetor got hold of 
this information, managed to figure out what the gibberish was, and 
managed to gain a competetive advantage.

(Nice story, but sounds kinda made-up to prove a point to me...)

The thing about a database is... the DBMS knows how to read the data. 
And if you change how the data is stored (e.g., add a new field, change 
a table from heap-organised to index-organised, etc.), as long as the 
DBMS still knows how to read it, the client applications don't need to 
*care*, and they don't break.

(Hell, if you add new fields or change the type of existing ones, you 
can even create a "view" for the old apps to work off. They'll never 
know the difference!)

At least, that's the PoV I got. I wasn't there, so...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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