Whereas principle F1 enables unambiguous identification of resources of interest, principle F2 speaks to the ability to discover a resource of interest through, for example, search or filtering. Digital resources must be described with rich metadata – including descriptors of the content of the resource referred to by that identifier. It is hard to generally define the minimally required “richness” of this metadata, except that the more generous and comprehensive it is, both for humans and computers, the more specifically findable (in a meaningful way) it becomes in refined searches. Descriptive metadata are, therefore, extremely important in cross-domain search and interdisciplinary use cases [A]. For centuries, it has been common practice in the scholarly community to clearly reference research results through citations. To enable findability, the metadata required for citations is the minimum requirement and a number of works have defined the required properties (creator, title, publication date, publisher, and identifier) in a variety of documents [B]. Other works defined additional core metadata requirements for data discovery which may serve as a guideline [C]. Community specific metadata requirements, for examples those created in Metadata for Machine (M4M) workshops, may include additional metadata properties.

While other principles specify metadata elements that must be present to support, for example, specific aspects of reusability (e.g. citation and license), principle F2 is primarily about discovery - that a digital resource that is well-described can be easily discovered even when the resource is unknown to the agent performing the search. Thus, this principle encourages data providers and domain experts to consider the various facets of search that might be employed by a user of their data, and to support those users in their discovery of the resource. To enable both global and local search engines to locate a resource, generic and domain-specific descriptors should be provided, that can be exposed to indexing by the relevant search facilities.