In the HCA metadata schema, types represent the various aspects of an experiment. The types themselves, however, are composed of smaller reusable schema elements called modules.
Modules contribute sets of properties with a common theme wherever they are included. Modules can also be included in other modules.
The use of modules helps to keep the HCA metadata schema both compact and self-consistent by allowing a schema structure representing a given concept to be defined once and then reused wherever it is needed.
Every metadata type includes a single core module which defines the type’s super class. For example, all of the biomaterials (e.g. Cell Line, Cell Suspension, Donor Organism, etc. ) include the Biomaterial Core module. The Biomaterial Core module contributes Biomaterial ID, among other properties to each of these types.
Similarly, all file types include the File Core module, all process types include the Process Core module and so on.
Entity modules are the main, general class of module. Entity modules model concepts such as Funder, Channel, and Probe. Entity modules are also used to represent the various ontologies used by the HCA metadata schema such as Cell cycle ontology .
System modules are created and populated by the HCA Data Portal during data ingest and processing. For example, the main System module is Provenance which models an entity's Document ID, Submission Date, and Submitter ID among other fields.