How do you justify to the person paying for it that you are are going to spend money to build essentially the same system?
Obviously in that:
1) It will completely work with your existing clients etc, because it does exactly what the old one does, with no wild new features and untested stuff.
2) It will bring your old legacy app up to date with a modern language, being able to run in modern hardware, maintained by readily available programmers for hiring, etc.
3) It will allow you to start to add all kinds of features a couple of years down the line, as the remake proves a success, and any minor issues are ironed out.
4) It's much less of a risk of some total rewrite, with a new architecture, ambitious plans, and the idea that you can just migrate the data and switch over, since those "second systems" tend to fail, and over-shoot their costs.
The only way to justify is if the maintenance costs are higher than the redevelopment costs.
You forgot the opportunity costs. Enabling them to be more agile, add new features, take advantage of modern pool of programmers, etc., is important, even if they have first to build an identically behaving version of their legacy app.
Comments
Obviously in that:
1) It will completely work with your existing clients etc, because it does exactly what the old one does, with no wild new features and untested stuff.
2) It will bring your old legacy app up to date with a modern language, being able to run in modern hardware, maintained by readily available programmers for hiring, etc.
3) It will allow you to start to add all kinds of features a couple of years down the line, as the remake proves a success, and any minor issues are ironed out.
4) It's much less of a risk of some total rewrite, with a new architecture, ambitious plans, and the idea that you can just migrate the data and switch over, since those "second systems" tend to fail, and over-shoot their costs.
You forgot the opportunity costs. Enabling them to be more agile, add new features, take advantage of modern pool of programmers, etc., is important, even if they have first to build an identically behaving version of their legacy app.