These days, having had a degree in IS for a while, I tend to apply an information-theoretic approach. What is real, if that is asking equivalently what is physical, is "just" information, information is physical or it has a physical basis; information occupies a volume but seems to be something that can project onto an area, maybe onto a line. As long as you can define a storage operation and the notion of transmitting information from place to place, you necessarily define a physical space. So does the vacuum store information? How is it written and on or in what?