Multi-dimensional Data Access minimal requirements

[Ray Plante]

Hi Tom,

Note that what you are calling "DataAccess" is the purpose of the 
AccessData specification (now being written up by Pat).  And, yes, it 
can be implemented independently of SIAv2.  In previous versions of 
SIAv2 (as Doug mentioned), the access-data capabilities was not yet 
split out.  

I agree with Tom (and Pat, as he originally explained) that specifying 
a circle is the easiest to deal with on the provider side, given all 
of the possible orientations, though it may under traditional use 
cases to be a bit counter-intuitive.  That said, a rectangular 
specification is also intended to be supported by AccessData 
(correct?), and I also agree with Andreas and Doug that the easiest 
way to handle this is with a position and size along the image axes.  

cheers,
Ray