In this chapter, we present our approach for representing mobility data, following the foundational ideas of Ralf Güting, who divides the design in two parts, the definition of an abstract model and its implementation through a concrete model. The driving idea of the abstract model, which is explained in Sect. 3.1, is the definition of abstract data types over infinite sets, together with appropriate operations. These abstract data types extend the classic base (nonspatial and spatial) types using time types, producing temporal types, such as temporal integer, temporal float, temporal Boolean, and temporal point. The data types of the abstract model must be implemented by a concrete model in terms of finite sets. Several concrete models can exist for the same abstract model. In Sect. 3.2, we adopt an approach referred to as the sequence representation. This approach, which is the one used in MobilityDB, is based on a hierarchy of temporal data types, where a temporal type has three subtypes, namely, instant, that is, an individual (value, instant) pair, sequence, that is, a sequence of (value, instant) pairs, and sequence set, that is, a sequence of sequences.