[golergka]

> They were stuck because they had no way to reverse engineer the requirements from the COBOL code, some of it going back 25+ years. Of course it wasn't documented, or if it was, the documentation was long gone.

Can you explain for people who never ever been close to such an environment how this can happen, and why do they still care about upholding the requirements they don't know about?

[fullwedgewhale]

Let's say you have a business process, like if a shipping manifest goes through any one of the following 3 cities, then you need to file form XYZ, unless the shipper is one of the following official government agencies and they've filed forms ABC and DEF. That was the original requirement in 1980. It was documented, put in a series of binders, and placed on a shelf.

1982, Adds another port to the list of special port cities, but only if shipping goods of type JKL or MNO. That change was documented in an inter-office memo and filed away. Except the only time you have the type of goods information is in a different module - so even though it pertains to the original business process, it's in another module that prints the ship's manifest to (physically) mail it to the insurer.

1989, the original requirements binders are moved to a storage facility.

1992, The memo is also sent to an archive facility. Original manuals have been destroyed because the records retention policy is 10 years.

1994, There's a change in the law and an emergency fix was put in, and the comments were put into the source code.

1995, The source code with the comments is lost, so an older version of the source code is recovered with the just the code change.

And so on and so on

Until 2015. You have 5,000 to 10,000 lines of code that deal with the original requirement. They're split into multiple modules. They reside in a source code base of 5,000,000 lines of code. The people that use your software have a combination of the software + a whole bunch of unwritten rules like: "If it's this country, and this port, and this port of origin - PF10 to get to the override screen and approve the shipment. Add 'As per J. Randal' in the comments."