Hey,
I thought a little more about that:
- Layer groups:
All the other map types like bing or google already bring several maps if you write <display_map service="openlayers" layers="bing"></display_map> for example, you get the Bing Streets, Bing Satellite and Bing Hybrid. For some image layers, I want the same. Think about a image of a location from different time periods for example. Instead of listing them all in 'layers', you should just have to call the group name and all of them should be available as base layers.
I think instead of a db or subpage solution, perhaps a solution where you could define several <layer> sections in one page would be even better. We could introduce a attribute vor <layer> called 'name' which gives the layer a name within the group.
if you write
<display_map layers="moon">0,0</display_map>
you will get all the layers defined on 'Layer:Moon' as base layers for this map. If you write
<display_map layers="moon|name">0,0</display_map>
you will just get the map defined on 'Layer:Moon' which has the attribute 'Name' with the value 'name' like:
<layer type="image" name="name"> ... </layer>
This would not give us the inherit feature but could be more convenient than having one page per layer instead of having one per group. It's at least better than the database solution I guess, still, the subpage solution would allow the inheritance feature.
Daniel