Conceptual Aspects: How Landmarks Can Be Described in Data Models - Landmarks: GIScience for Intelligent Services - page 128

geographic object has been created in OpenStreetMap, it can be tagged by additional
information. This latter property offers the prerequisite to implement our formal
landmark model presented in Sect. 4.2.2 by tagging objects with context-dependent
properties of landmarkness. According to the model above, a tag should store at
least a name, a context, and measures of landmarkness.
Tags are key-value pairs describing properties of data types of all dimensions,
nodes, lines or areas. OpenStreetMap comes with a long list of conventionalized
tags , 9 but users can add further tags. Such further tags, however, need then also to
be introduced in the mapping and navigation services based on OpenStreetMap.
For each new tag a community has to be ready to use them, and to use them
consistently. Without community support, tag use will remain local and probably
fade out over time.
It is straight forward to define key-value pairs to represent the landmarkness of
the objects according to the above formal model (Sect. 4.2.2 ) in OpenStreetMap, and
it is also straight forward to develop mobile applications that support the community
in capturing this landmark information [ 17 , 49 ] and using this landmark information
in services. In lack of properly defined key-value pairs no community-accepted and
supported landmark tag has been introduced in OpenStreetMap so far.

4.3.3 Landmarks in OpenLS

The closest contender for a suited data model is probably an inclusion of landmarks
in OpenLS [ 24 ] .
OpenLS is an international standard by ISO and OGC . 10 OpenLS describes an
open platform for location-based services. Among its core services is a route service.
OpenLS specifies primarily the interaction between client and server and the format
in which the transferred data is encoded. The role of a route service in OpenLS
is to determine a travel route between two points and to collect the navigation
information required to communicate this route.
For the interaction between client and server OpenLS comes with an XML
schema for location services, called XLS. XLS is an exchange data model for route
services, this means for structuring and encoding requests and responses regarding
route descriptions. XLS only caters for POI, and does not yet cater for an abstract
data type landmark . However, XLS offers explicitly an optional attribute, which can
serve different purposes, among others also describing a landmark. This attribute
allows for providing the name of the landmark and its location with respect of the
side of the route. Other information about the landmark cannot be encoded in this
attribute, such that information necessary for the cognitive ergonomic use of this
landmark cannot be encoded and is lost.

9 http://wiki.openstreetmap.org/wiki/Map_Features , last visited 3/1/2014.
10 http://www.opengeospatial.org/standards/ols , last visited 3/1/2014.