# Overview

## Introduction

This is the proposed ontology to integrate geolocation information in the nepomuk set of ontologies. It defines a place in the space with the class mlo:GeoLocation. A place can be defined in different ways:

1. As a Box (using the class mlo:GeoBoundingBox and the property mlo:asBoundingBox)

2. As a point with coordinates (using the class mlo:GeoPoint and the property mlo:asGeoPoint) as a single point in the space with its coordinates

3. As a postal address, with the text description (using the class nco:PostalAddress from NCO ontology and the property mlo:asPostalAddress)

These three representations are not exclusive, but is responsability of the applications to keep the data consistent.

Some places in the space has an special meaning, E.G. premises, buildings or services. This fact is represented in the ontology with the class mlo:Landmark. The title and description of the Landmark itself can be set using the nie:InformationElement properties (nie:title, nie:description, ...). A location is linked with a landmark with the property mlo:location inherited from the superclass Information Element.

Landmark can be grouped in categories. For this reason, the ontology provides a property mlo:belongsToCategory that links a Landmark with the class mlo:LandmarkCategory . The ontology includes also a predefined set of instances, very common an a de-facto standard in the industry.

## Considerations

A mlo:Landmark is linked with its location using the property mlo:location, inherited from its superclass nie:InformationElement.

All classes in the ontology are subclasses of nie:InformationElement. It is not indicated in the graphic for the sake of clarity.

The three possible representations of a location (i.e. mlo:GeoPoint, mlo:GeoBoundingBox, nco:PostalAddress) are properties (and not subclasses) of the location object (instance of mlo:GeoLocation).

## Contract with applications

We want to put special emphasis in the point that the applications must keep the different representations of the points consistent. Basically a point in the space is very unlikely to change (the point is there or not), but it is not difficult to assume that some application can complete the information, taking the postal addresses of the points without coordinates, and set the coordinates using some web service.

A box is considered as a 2 dimensions area orientated to the north, aligned to parallels and meridians. The area is defined with two points: the southern east point (down left corner, in the mlo:bbSouthEast property) and northern western point (upper right corner, in the mlo:bbNorthWest property).

mlo:LandmarkCategory has a property mlo:isRemovable to mark is the category is predefined and shouldn't be deleted by the applications. Tracker (and probably other backends) doesn't enforce applications to respect this value, but consider it a gentleman agreement.

### Graphical Overview

Notation defined in this page