An empty dimensional_model object is created in which definition of facts
and dimensions can be added.
Details
To get a star schema (a star_schema object) we need a flat table
(implemented through a tibble) and a dimensional_model object. The
definition of facts and dimensions in the dimensional_model object is made
from the flat table columns. Each attribute can only appear once in the
definition.
See also
Other star definition functions:
define_dimension(),
define_fact()