Re: Dates and triggers.

["Rob Dixon" <rob.dixon@xxxxxxxxxxx>]

David

The following idea will not necessarily help you with your immediate
problem, but, as you have been an active participant in the Design shift of
view Thread, I thought you might be interested in how, conceptually, a
Neural Database (NDB) might cope with triggers.

Perhaps the most obvious difference between the Neural Database and other
databases is that the NDB is data driven: this means that it is always
looking for data to keep it "moving".  If the NDB looks for a record in a
particular context, it will either find one or it will not.  This might be
regarded as a binary switch.

Either situation could be an error.  Options in menu records in the NDB
could determine what action is to be taken.

If there is no record, the NDB might be set up to go back automatically to
the previous menu, read the next menu record and look for a record
elsehwere, and perhaps continue this process until it finds a record or
there is nowhere else to look that has been defined.  Alternatively, the
NDB might be set up to add a record.  This might be done with or without
operator prompting and might be a piece of independent data (such as a
dimension or a value) or a relationship.  The relationship(s) that are
valid at this point are also defined in the NDB.

If a record is found, the NDB might be set up to move on to look for other
data to which the record found acts as a "pointer" (not an address
pointer), or it might be set up to delete the record found, or display it
to the operator for change, etc..

In either situation, the NDB could also be set up to issue an error message
to the operator or call a program to provide a special function not
available as standard in the NDB, or it might be set up to roll back a
transaction not yet complete and issue a message, etc..

As an example, in a pharmacy, a prescription might be for what in the UK is
known as Warferin, an anti-coagulant also used as rat poison.  In the UK,
and probably 
elsewhere, pharmacy systems must check previous dispensing history for the
patient, even for over the counter drugs such as aspirin.  I understand
that Warferin and Aspirin together are not a good mix.  It is possible
using the NDB to set up an unlimited number of contra-indications (I think
that is the correct medical term) for each drug and the dispensing
application will automatically search the patient's dispensing history.  If
it finds no contra-indication for the drug being dispensed, it will allow
the drug to be dispensed (providing there is enough stock).  If for a
prescription for Warferin, it finds that the patient has previously been
dispensed aspirin at any time, it can prompt the pharmacist  to ask the
patient if they are still taking them or have any left, before the
transaction is allowed or cancelled.  All of this could be defined using
the NDB which has its own trigger mechanism.  No program coding is
required. 

All dates in the NDB would be stored as 9 digits - YYYYMMDDA - where A is
an accuracy  code, normally set to 5 (exact) for commercial transactions
when the date is known.  It can also be used to indicate, before, about,
after, etc.  Options in the NDB indicate how the date (and time if
necessary) is to be displayed (in US,  European or Julian formats, 2 or 4
digit years, etc.).  Times are also stored as 9 digits - HHMMSS.SSA, the
last also being an accuracy code.

Rob Dixon 
Erros plc

----------
> From: David Morris <dmorris@plumcreek.com>
> To: MIDRANGE-L@midrange.com
> Subject: Dates and triggers.
> Date: 31 July 1998 20:38
> 
> Data base experts,
> 
> On files with triggers, it appears as if dates must be valid in the
buffer before the trigger is fired.  We were hoping to be able to reformat
dates entered in an invalid format in either the pre-update/write action. 
The incorrectly formatted date never gets to the trigger.  A date or
timestamp exception prevents the trigger from executing.  Is there any way
around this?  We do not have control of every application to reformat the
date before the trigger is fired.
> 
> Thanks,
> 
> David Morris

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