A workflow is a container object that aggregates information required to fit and predict from a model. This information might be a recipe used in preprocessing, specified through add_recipe(), or the model specification to fit, specified through add_model(), or a tailor used in postprocessing, specified through add_tailor(). The preprocessor and spec arguments allow you to add components to a workflow quickly, without having to go through the add_*() functions, such as add_recipe() or add_model(). However, if you need to control any of the optional arguments to those functions, such as the blueprint or the model formula, then you should use the add_*() functions directly instead.