Chapter 1. Introduction

MobilityDB is an extension of PostgreSQL and PostGIS that provides temporal types. Such data types represent the evolution on time of values of some element type, called the base type of the temporal type. For instance, temporal integers may be used to represent the evolution on time of the number of employees of a department. In this case, the data type is temporal integer and the base type is integer. Similarly, a temporal float may be used to represent the evolution on time of the temperature of a room. As another example, a temporal point may be used to represent the evolution on time of the location of a car, as reported by GPS devices. Temporal types are useful because representing values that evolve in time is essential in many applications, for example in mobility applications. Furthermore, the operators on the base types (such as arithmetic operators and aggregation for integers and floats, spatial relationships and distance for geometries) can be intuitively generalized when the values evolve in time.

MobilityDB provides the following temporal types: tbool, tint, tfloat, ttext, tgeompoint, and tgeogpoint. These temporal types are based, respectively, on the bool, int, float, and text base types provided by PostgreSQL, and on the geometry and geography base types provided by PostGIS (restricted to 2D or 3D points).^[1] Furthermore, MobilityDB uses four time types to represent extents of time: the timestamptz type provided by PostgreSQL and three new types which are period, timestampset, and periodset. In addition, two range types are defined in MobilityDB: intrange and floatrange.