There doesn't have to be one database schema, or even one data interchange format. There only has to be an agreed upon semantics that can be mapped on to differ

There doesn't have to be one database schema, or even one data interchange format. There only has to be an agreed upon semantics that can be mapped on to different data interchange formats. Here is where linked data/semantic web comes in. For instance json-ld allows you to use json as you normally would, but add a schema that allows others to know what all your fields actually mean.