The best thing that can be used is open data. What is open data anyway? This is the type of data that is available to everyone and can also be reused by everyone depending on their needs. The best thing about this is that people who get information from open data do not have to worry about copyright issues and so much more. You can also republish the data if you wish just.
The data can be useful especially if there are some things that you want to clarify. There are some people who are not too sure about using other types of data especially if they are patented. The other choices available may be helpful to a certain extent but open data can be helpful for marketers.