A package for spatial data classes: request for comments

Barry Rowlingson wrote:

To be really useful, the class should include vector (polygon) data,
and probably line elements. For this, I need help. The simples 
approach
would be to extend SpatialDataFrame to SpatialDataFramePolygon,
and add for each row add the corresponding polygon.

 I think you need to stop thinking about building classes at the 
moment, and to think about specifying _interfaces_. What methods do 
we want for spatial data? How will functions get the spatial data out 
of the objects? Then we can build classes that implement these 
interfaces.

Baz, I agree that interfaces are important. Still, concentrating on 
interfaces _only_
does encourage package writers to come up each with a new set of 
spatial classes
-- something I would like to discourage: sharing more code makes the 
code more
reliable.

I did build upon your idea of sp.coords, but called it coordinates, 
and used reference (column name/numbers) instead of actual values:

coordinates(meuse) = c("x", "y")

I prefer coordinates because at some stage the S3 method mechanism may
interpret sp.coords as an sp method for a coords class.

My question, in your perspective, would be: which methods do we need 
for
a generic class containing vector/polygon data?

E.g. how is,

polygons(world) # gets or sets the polygons, as a list of 2 col 
matrices
polygonAttributes(world) # gets or sets the polygon attributes, as 
data frame
--
Edzer