Intelligent Software Building: products, platforms, programs

On a regular basis I see folks who are trapped by the siren song of reusable code.

Now, don't get me wrong.  Reusing code is a wonderful thing, and it's a good goal, but it's important not to get carried away.  There are basically three levels of reuse:

1. Programs - this is when you reuse parts of your own code, on a personal sort of level.  You built these routines and snippets, documented them and like them.  They're something you've done before and know you want to do again, so you were kind and thoughtful to yourself and wrote it in a way that you would recognize.

2. Platforms - this is when you specifically plan for reuse when you're writing something.  Platforms refer to a broad area of capability that is important and that you'll want to build on.  Platforms require serious forethought.  They also require serious documentation and some support.  Typically this is something you will share with other members of your team.

3. Products - this refers to a software platform that you want to make broadly available.  When you create a software product you absolutely have to have clear documentation in and out of your code.  You have to plan for wide deployment and you have to have support people in place.  When changes are made, you have to have a thorough test apparatus in place to understand what the impact of your changes will be on others who have built their software with your product.

especially to yourself...

Be kind to the person who will inherit your code, because often that person is you. 

Many times I have cursed the me of weeks or months ago for leaving a mess for me.  When I'm kind to me, I always appreciate it.  Reuse of your programs is just good practice, and naturally happens when you're writing thoughtful and clean.

After you've experienced those benefits a few times, you'll start dabbling around with platform style reuse.  You'll think "hey!  that little block of code has been so useful to me, I bet others would like it!"  Before you know it, you have a whole set of interconnected things that you've put together and share.  You probably don't have any sort of obligation to support it, but it's fun and you're supporting your own work through the thing anyway, so it just makes sense. 

Ain't nothin' wrong with Platform style reuse.

Where you have to think long and hard is around the Product-style reuse.  This makes sense if your goal is to sell this code as a development tool.  This is something like D3, or Telerik, or the Unreal Engine, or Havok or anything like that.  More often than not, I see this when developers fall in love with their own, potentially reusable programs, assemble them into a platform and then decide the whole world needs it.  You will have tons of support work to do.  You will have to maintain forward and reverse compatibility.  

If this is some sort of exercise in self-love, you need to stop now and slowly back away.  Really, unless you're planning on making enough revenue from this (or if internal facing, saving enough effort) to justify several developers and a testing team, this is just a bad idea.

Sometimes a platform may naturally find demand in the market.  Maybe the platform you built is truly wonderful and well documented and bullet-proof and you really really want everybody talking about how awesome you are... Even then, don't do it unless you have the support staff.  The first time some package you're including gets depricated or MS rolls off some capability you're counting on or any other of a million possible things, you're going to have all those people who were singing your praises on your IM, demanding immediate fixes...