[hvidgaard]

It is possible to make a schema such that you can add whatever you want. And this only applies to exporting the data anyway.

[sjdchid]

Ok, so you can export it, but only in a format that is useful to a programmer.

[distances]

Yes, I didn't mean it would have to conform to a standard of any kind. You'd get the data; it would be up to you (or a service you choose to use) what to do with it.

Of course this wouldn't lead to any magical inter-operation of services, but that wouldn't be the point anyway.