A rule in a semi-new concept in ComputerScience for making a DataEcosystem. The idea is to contain data (in a struct or other named entity) for which you have a useful categorization (so others can use it) and maximize these groupings by finding rules which consistently represent and support the unseen relationships of data objects.
This rule must be balanced with a counteracting rule: DontContainTheUnknown. If you don't have a category that represents your data, leave it naked.
See UnifiedDataModel