[wisnesky]

Sum types are harder to express as data integrity constraints that product types - for example, Horn clause constraints can be used to express that a table is a product (or limit, more generally) of other tables, but to express that a table is a co-product (or colimit, more generally) requires a stronger logic (handling disjunction, for example). This has implications for data processing algorithms such as the chase that depend on the strength underling logic.