W3C + WAP Workshop Position Paper

Charles Roche

Mobile GIS Ltd

Cork, Ireland

Toward Interoperable Geographic References

Location-based services depend on the match between a position defining the location of the mobile client and information in geo-referenced databases. There are many ways to make a geographic reference -

  • by name,

  • by co-ordinates,

  • by relationship to other geographic features, or

  • by proprietary or authority-supplied permanent identifiers.

The use of a name, a category, and a relationship to another feature is the most common approach used by humans in natural language references. For example, a person might indicate that their position was at the Black Man, a pub located at a road junction to the north of Cork City. They might want to know how to drive to the nearest Shell petrol station open at the current time.

We often think of navigation sensors or positioning technology based on properties of mobile telephone infrastructure as the source of position information. In fact, the most natural position information at the man-machine interface is that based on natural language. The key question for providers of position-dependent services is how to reliably convert to and from natural language geographic references.

A first step would be the definition of a standard container for a geographic reference in natural language. This container would need to model 

  • a name

  • - the natural language used for the name

  • - the script  used for the name

  • - the encoding  used for the name

  • the category of geographic feature

  • - the natural language used for the category

  • - the script used for the category

  • - the encoding used for the category

  • a small set of relationships such as

  • - disjoint from

  • - contains

  • - inside

  • - overlaps

  • - meets

Such a container could, for example, be defined by an XML DTD and many of the elements could build on existing ISO standards or IETF recommendations.

Logical next steps would be to define standard methods for

  • requesting an equivalence test between the contents of two geographic reference containers, 

  • transforming contents while maintaining equivalence (translation), and 

  • negotiating modifications to geographic reference container contents to achieve equivalence between a human request at a man-machine interface and the stored contents of a database containing representations of geographic entities relevant to the delivery of location-dependent services.