Can I write this in English:

The structure is either determined beforehand or is decided on based on the available data.
It concerns the first on (in bold). Should it be there or not? The sentence is a shortened version to be able to ask the question; it is a sentence that belongs in a scientific article. It looks weird with the two on's in such a close succession, but there is a difference between "you decide on something" and "you decide something", so I think it should be there... Or should I just use a different verb?