On Wed, 2006-03-15 at 15:20 +1100, Helen Borrie wrote:
> At 12:58 PM 15/03/2006, you wrote:
> >On Wed, 2006-03-15 at 00:06 +1100, Helen Borrie wrote:
> > > No accounting standard is allowed to override
> > > best practice in database design.
> >
> >Explain that to the former bosses at Enron :o)
> >
> >Accounting standards, rather than overriding best practice in
> database
> >design, define best practice in database design for financially
> critical
> >systems.
>
> No way. No way. Best practice *includes* protecting the integrity
> of externally imposed data requirements and *not* making internal
> data integrity dependent on external requirements, actual or
> potential.
>
> A primary key is an entirely internal matter. The accounting
> standards are met entirely by associating the unique protected
> document id (such as invoice id) with the primary key. Database
> design best practice is NOT met by making the document id perform the
> function of the primary key.
>
> There's nothing to stop you putting a UNIQUE constraint on the
> protected field: it's what you must do to comply with the accounting
> standard. Furthermore, you can set up all the protections stipulated
> by the accounting standard by applying constraints and triggers. You
> don't spin protected document ids out of calculations based on
> pre-existing documents. You create an engine for it that is used for
> no other purpose and never allows an update. Down the chain of
> operating processes, the protected document id is literally read-only
> and is never seen again in the abstract storage. Foreign keys and
> everything else in the system refer to this totally-protected thing -
> "invoice" or whatever, only by way of the PK of the master
> entity. End-users never see the technology - they never lay an eye
> or a finger on a structural object like a primary or foreign key.
>
> That's the science - the engine behind what you present to the
> customer to meet the requirements. The accountant has no more place
> telling you how to build the engine that he does telling the
> equipment-maker how to wire the adding machine.
>
> ./heLen
>
>
>
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