True, typically you don't know in advance of a data mining operation. Nonetheless, you have some invariants that you know you'll need and these can be modelled with a schema.
Additionally, when attempting to put a model into production, you'll normally know what it is you need, and this can be put into a schema for ease of interoperability with other requirements (CMS, booking etc).
Additionally, when attempting to put a model into production, you'll normally know what it is you need, and this can be put into a schema for ease of interoperability with other requirements (CMS, booking etc).