Re: database integrity

mountain man wrote:

> Q1: What is database integrity?
>
> A1: A measure of the self-referential consistency of all
> the relations existent between the physical data elements
> defined in the schema of a database.
>
> Any disagreements, improvements, comments?
>

Two big areas:

1. Free from corruption
2. It is valid, or more verbosely, adheres to validity rules

Item 1 is pretty simple, it means only that the disk drive didn't fail, or the magtape didn't get folded, or the punched card didn't get bent. Corruption is one way that data can become invalid.

That leaves Item 2, which we expand by determining the allowable kinds of validity rules. The basics are domain integrity, entity integrity and referential integrity. Practically speaking I have found it necessary to add only comparative constraints between a columns.

One question on my mind is the change in rules over time. Do we say:

1. Data is valid if it adheres to all existing biz rules, OR:
2. Data is valid if it adheres to rules that were in force when it was inserted or updated.

-- 
Kenneth Downs
Secure Data Software, Inc.
(Ken)nneth_at_(Sec)ure(Dat)a(.com)