https://chronologist.com/blog/2012-07-27/theory-of-constraints-and-software-engineering/
- Throughput:
TE
is the rate of cash generated through delivery of working code into production. It is computed as sales price minus direct costs, such as packaging, delivery, installation, training, support, and networking. - Investment:
I
is all money invested in software production systems plus money spent to obtain ideas for client-valued functionality. This does not apply to time spent by staff (that's Operating Expense). It does apply to the money spent on by-the-hour contractors. - Operating Expense:
OE
is all money spent to produce working code from ideas. It is primarily direct labor of software engineers, but it also includes selling, general, and administrative costs. So, our fixed overheads.