Hi Colin,

I am not sure what you mean. Let me try an example:
I am aware that my Oregon 450t needs e.g.
tourism=camp_site [0x2b05 resolution 24]
instead of
tourism=camp_site [0x2b03 resolution 24]
which is used in the default style.

If I got you right, you want to create some kind of database to keep track of these
differences and a style that uses a symbol to reference the database.
So, for my example, we would have a database with a symbol
"camp_site_poi_type" and a default value 0x2b03 and a special value
for the Oregon 450t containing 0x2b05.
The style would then use something like

tourism=camp_site [db:camp_site_poi_type resolution 24]

When reading the style, mkgmap could look up the database to find
the right value.

If the database would use SQL, we probably need a few tables
for device types, groups of device types, firmware versions, etc.
Without SQL, it might be another XML file.

Any ideas how many differences we have  and how they could be stored?

Gerd