# Definitions

A "Map Object" in HERE Indoor Map stands for the abstraction of a real-world object with attributes that are relevant for geographical applications and for adhering to certain conventions.

One Map Object can be represented by one GeoJSON feature. MOM further distinguishes certain Feature Types using momType, which are Map Objects that represent the same class of real-world feature and carry the same set of attributes that share the same momType. Due to the close alignment with GeoJSON concepts, all MOM feature classes have Id, geometry, and properties.

MOM also defines various re-usable and shared component classes which do not have an ID. These are the building blocks for MOM features. Due to their lack of an identifier, they are valid only within a feature definition.

## Differences in data model definitions

Some data structures have a different definition in the data model than in the serialized JSON data. For example, a point class has type, longitude, latitude, and elevation properties in the data model, but GeoJSON specifies a point with two properties, type and coordinates, where coordinates is an array of longitude, latitude, and optionally altitude, as numbers.

For example:

"geometry": { "type": "Point", "coordinates": [120.68093, 24.2114] }


Other GeoJSON types are defined similarly in GeoJSON, but the HERE Indoor Map data specification specifies them using the point class as a basis, instead of extending the coordinates-array dimension like the GeoJSON does. When serialized into JSON data, indoor MOM follows GeoJSON definitions, as is visible in the shared indoor maps, and also in the sample data included in this guide.

However, the point class may also be serialized directly to a plain number array of coordinates, without any sub-properties. It is not a generic GeoJSON point, but directly relates to the coordinates in an array, such as “point”: [45.2433, 11.4332]. This is because it is not a generic geolocation, and instead the type is a known point. This is also the case with ElevationPoint.

The target audience is expected to be familiar with general concepts of geospatial data models used in the context of map rendering, route calculation, route guidance, location search, and related use-cases. The metadata required for converting other map data models to MOM is either provided as part of the MOM schema or through further HERE reference documentation.

The default persistence representation complies with the GeoJSON standard. While the model is defined in a target-agnostic Domain Specific Language, the JSON Schema is one available reference specification against which clients can verify their content. This specification is a specification of the software model used to generate HERE Indoor Map MOM data. The serialization of the data to JSON does not follow the software model specification exactly.