Data model

A data model organizes data elements and standardizes how the data elements relate to one another. Since data elements document real life people, places and things and the events between them, the data model represents reality, for example a house has many windows or a cat has two eyes. Computers are used for the accounting of these real life things and events and therefore the data model is a necessary standard to ensure exact communication between human beings.

A data model is a set of symbols and text used for communicating a precise representation of an information landscape. As with a model of any landscape, such as a map that models a geographic landscape, certain content is included and certain content excluded to facilitate understanding.

Data models are often used as an aid to communication between the business people defining the requirements for a computer system and the technical people defining the design in response to those requirements. They are used to show the data needed and created by business processes.

Data model (ArcGIS)

In ArcGIS, a data model a set of database design specifications for objects in a GIS application. A data model describes the thematic layers used in the applications (for example, hamburger stands, roads, and counties); their spatial representation (for example, point, line, or polygon); their attributes; their integrity rules and relationships (for example, counties must nest within states); their cartographic portrayal; and their metadata requirements.

See also

References

Data model (GIS)

A data model in geographic information systems is a mathematical construct for representing geographic objects or surfaces as data. For example, the vector data model represents geography as collections of points, lines, and polygons; the raster data model represent geography as cell matrices that store numeric values; and the TIN data model represents geography as sets of contiguous, nonoverlapping triangles.

Representing three-dimensional map information

There are two approaches for representing three-dimensional map information, and for managing it in the data model.

Vector-based stack-unit

Vector-based stack-unit maps depict the vertical succession of geologic units to a specified depth (here, the base of the block diagram). This mapping approach characterizes the vertical variations of physical properties in each 3-D map unit. In this example, an alluvial deposit (unit “a”) overlies glacial till (unit “t”), and the stack-unit labeled “a/t” indicates that relationship, whereas the unit “t” indicates that glacial till extends down to the specified depth. In a manner similar to that shown in figure 11, the stack-unit’s occurrence (the map unit’s outcrop), geometry (the map unit’s boundaries), and descriptors (the physical properties of the geologic units included in the stack-unit) are managed as they are for a typical 2-D geologic map.