As discussed in [Rod01], in most systems, time is considered to be unidirectional and linear. It is usually modeled as a discrete variable taking integer values that represent days, hours, and so on. On the other hand, space is considered bidirectional and, especially in geographic systems, nonlinear. Space is represented with real numbers and the granularity is usually small. For example, it can be in the scale of feet or meters in an area that represents an entire city.