Coded Record Structures

[Edis, Bob]

G'day Pablo

I think the PHD is actually an early attempt (and somewhat successful) at
OOP.  In you case you can have a single RMS file but have multiple 'views'
of the data using different record definitions in the dictionary.  It is far
more maintainable to have this logic in a data dictionary than program code
- when someone needs to find that logic in the future it'll be in one place
rather than several different versions in many pieces of program code.

Think of the FILE and primary RECORD definition as a CLASS and each
subsequent RECORD definition as an OBJECT of that class.  I think of USAGES
and ELEMENTS in the same way.

Several ERP applications still use 'control' files, even those utilizing
RDBMS engines.  These are non-relational, non-normalised data stores used by
the application to maintain configuration data.  Two examples, one
PowerHouse and the other BASIC, are Visibility and Karmak.  The former makes
good use of many RECORD definitions with multiple structures and redefines
as well as SELECTs to use this control file.  The latter relies on BASIC MAP
files to do the same thing but in a less elegant way.

To achieve the same thing in a RDBMS would require multiple views of a
control table.

I like the idea of a central data dictionary when programming in any
language.  It helps to enforce standards and keeps the data logic in a
central location.

Regards,
Blue

-----Original Message-----
From: pablo grim [mailto:pablow666@gorge.net]
Sent: Wednesday, June 20, 2001 2:57 PM
To: Edis, Bob
Subject: Re: Coded Record Structures


Hi Blue,

Sorry this is confusing.  Probably because I am so confused I can't ask a
coherent question. 

The Social Security Admin has changed their specs for W2 electronic
submittal.  I am replacing an existing W2 application to meet the new specs.
The existing app uses Coded Record Structures for the W2 file.  The
requirements for the W2 file include about a half a dozen different record
structures of fixed length.

I'm trying to decide whether or not to stick with the coded record structure
technique or to simply go with 6 separate files that can be merged together
using VMS utilities.  The coded record structure thing just seems kind of
cryptic and well, arcane.  I've been programming in powerhouse for 15 years
and have rarely come across it.  Might be easier for whoever encounters this
at a later date to have it implemented in a more straightforward manner.
And I'm wondering if a throwback technique such as this will continue to be
supported in the long run.  On the other hand it does have a certain
elegance to it and automates some of what would otherwise need to be coded.

Of course there is a place for code and a place for metadata.  This
technique seems to get those places mixed up and may cause confusion.

tx
p


> From: "Edis, Bob" <bob.edis@fleetpride.com>
> Date: Wed, 20 Jun 2001 14:21:41 -0500
> To: "'powerh-l@list.swau.edu'" <powerh-l@lists.swau.edu>
> Subject: RE: Coded Record Structures
> 
> G'day Pablo
> 
> Was this message of yours part of a discussion with someone else?  I'm not
> sure I understand it and what you are asking?  Can you provide some
examples
> please?
> 
> Regards,
> Blue
> 
> -----Original Message-----
> From: pablo grim [mailto:pablow666@gorge.net]
> Sent: Wednesday, June 20, 2001 2:09 PM
> To: powerhouse
> Subject: Coded Record Structures
> 
> 
> VMS 7.1
> Powerhouse 7.4f4
> 
> I'm curious about the purpose of these coded record structures.
> Specifically the "select item" in the record structure.  Why is this
> functionality in the dictionary rather than in the code?  Isn't this a
> function that the programmer could control in code.  It's kind of hidden
> away there in the dictionary.
> 
> Also, I was wondering about the efficiency of this technique.  When
> retrieving data, is it a sequential read using the code value?  Since the
> coded item is common to each variant record in the file, couldn't
> (shouldn't) it be defined as an index for faster reads?   Can this element
> be defined both as a "select value" AND as an index?
> 
> Are select values REQUIRED for coded record structures or will Powerhouse
> (or RMS) allow the user to create a file with more than one variant record
> structure and NO coded values?  Such that the programmer could control
> update and retrieval directly via the code.
> 
> I guess I'm quite lost as to the nature and purpose of the select value
item
> in this interesting data structure.
> 
> thanks
> 
> Paul Grim
> Progressive Computing
> 
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