More comments on the ontology

Hi,

Here are more comments on the ontology:

+ We should define a better URI for the ontology. What about something like

 http://www.w3.org/2007/DCO

+ URIs for well-known instances in the ontology. For example, for the 
ImageType class we have 4 well-known instances that represent well-known 
image types. Unfortunately the URIs for these instances are ugly (the 
number that automatically generated Protege).
I think that the URIs representing this kind of instances should be very 
well-known, such as http://www.w3.org/2007/DCO#gif, etc.
I think that the ontology should provide the normative "constants" to 
identify this kind of well-known values and we should URIs for 
representing this kind of things in the DDWG API. Fortunately there is a 
utility called SchemaGen that comes with Jena that might allow us to 
create all the well-known set of constants.

Best Regards