Re: Legacy question -- RPG400-L

We have some programs that have hard-coding, in the logic phase of a
program. I am thinking it may be interesting to put these together into
a database thereby use this in the code instead. Usually these are
assorted 'exceptions to the rule' accounts.

Anyone who has done please share your experience, ideas on this.

The more generic you make this 'business rule' table, the moresophisticated your documentation and maintenance must become. Examplesmay be useful.

Let's say you're doing credit checking, and some of your biggestcustomers would fail that. Your code has a bunch of


if cust = 123 or
   cust = 345 or...

So you decide to move those exceptions out to a table. Now your codelooks like


cust chain creditexcept
if not %found
  ... do normal credit check
endif

Your documentation says that to make a customer exempt, add his numberto the creditexceptions file. For maintenance, you may only need DFU.

Now think of the situation if you have many hundreds of exceptions, allgrouped by customer range;


if (cust >= 123 and cust <= 199) or
   (cust >= 223 and cust <= 299) or
   ...

You'd have two columns in your file, a CHAIN and some compares. Yourdocumentation would require noting the lower and upper limits, and ifyou want to exclude a single customer, you need to specify the samenumber in both columns. Maintenance could still be DFU, but it nowbegins to dawn on you that if you delete a customer from your masterfile, there are orphan rules left in the credit exception file. Need toadd that logic to the master maintenance.

It gets more complex when you want to name your rules, have one ruleinvoke another and so on. You can certainly move the logic out of thecode and into the tables, but you'll be creating a fairly complex set ofinterrelated tables, and pretty soon, DFU won't be good enough to keepthe rules base in synch.

There's no right or wrong here, only how much time and effort you'll beexpending in order to make the rules base more flexible (and presumably,changeable by the end user.)

I think that in general, vendors tend to be more interested in tabledriven systems than companies writing software for their own consumption.

  --buck