The subscription based software model is already mainstream, with 40% of software vendors reporting that they offer some form of subscription based offerings. However, the advent of SaaS (Software as a Service), multi-core processors, and virtualization (in effect creating "virtual machines" in a software environment were no hardware exists, thereby allowing many physical computers to be consolidated into a few servers that host the virtual machines), are causing both vendors and customers to rethink how they measure and charge for the right to use software.