Talking to large corporations on the subject of demand management in the last few months, i notice that the common process of demand management looks a lot like this:
1. Gather demand
2. Map demand on services (e.g. applications), business lines, and business/IT strategy
3. Prioritize demand
4. Create business cases (investment decisions) for demand
5. Implement — approved — demand in programs/projects
6. (Continuously) monitor performance of programs/projects that implement demand
7. (Continuously) monitor business cases based on key (financial) indicators such as net present value, internal rate of return, payback period — also after delivery of demand
8. Periodically re-evaluate investment portfolio of demand implementation based on monitoring information
This process enables a clear view of IT demand of the business lines, proper controls to approve an investment, contionous monitoring of implementation with the ability of feedback to the business lines, and proper controls for evaluation of IT investments. Basically, this process is the heart of IT Business Alignment.

