 The aforementioned words ‘instance’ and ‘display’ (used interchangeably here) can be applied to both interactive and non-interactive works characterized by a two-level ontology. Nevertheless, there are significant metaphysical differences between works like an interactive digital installation or videogame and others like a digital photograph. One of the more significant distinctions has to do with the structure of the displays; displays of interactive works are variable in ways the displays of non-interactive works are not (Lopes 2010). More precisely stated, the displays of interactive works are considered variable if they have a succession of states or they are repeatable (Lopes 2010: 37–38). To characterize the first kind of variability, consider the following description of the digital installation “Universe of Water Particles on a Rock where People Gather” (henceforth, where People Gather) by TeamLab: