Change to Thing Location Model

[alexrobin]

I suggest modeling Thing location as a particular kind of Datastream whose result type is a location vector.

Taking into account my other issue #131 regarding the Thing model, a location datastream could be equally attached to a System, a Thing, a Sensor, an Actuator, thus allowing one to provide (fixed or variable) location in a consistent way for all these entities. (Note that in this case the FeatureOfInterest of observations in the location Datastream should be the System itself)

[liangsteve]

Summary of bi-weekly telco discussion:

Location entity works when

• Location instances are limited or not generated on the fly (e.g., administrative units, rooms, buildings)

Location entity doesn’t work (i.e., not efficient) when

• Location entity is a simple geometry (moving car)
• For a moving car with sensors
• Location, Observation, FeatureOfInterest are updated frequently

Note:

• It’s possible to optimize it from the underlying implementation.
• Location, HistoricalLocation, FoI can be optimized for frequent update (without considering reusability).
• It's possible to have a STA implementation dedicated for moving things (i.e., with a different underlying database model and implementation)