A namespace is a directory of concepts that are used to identify and refer to entities within a dataset. Namespaces can be internal, used as a basis for minting Uniform Resource Identifiers (URIs) for a discrete dataset, or they can be external ontologies, vocabularies, and thesauri that could be either encyclopedic or industry-specific. It is best practice to use or extend a pre-existing vocabulary and link to that vocabulary using stable URIs provided by their namespace, rather than build a bespoke vocabulary. By using standard vocabularies maintained within stable namespaces, the achievements of Linked Open Data (LOD) are realized.
- The following example shows the declaration of namespaces for Y90s Personography in the TTL file header. Namespaces provide URIs for each listed entity. The namespaces above consist of a domain name and a path, as well as a prefix that allows shortening of resources within the TTL file (for example, bf:title would refer be a truncated version of http://id.loc.gov/ontologies/bibframe/title). Declaring and using namespaces allows both machine and human readers to differentiate between identically named elements from multiple datasets.
@prefix bf: <http://id.loc.gov/ontologies/bibframe/> .
@prefix bibo: <http://purl.org/ontology/bibo/> .
@prefix crm: <http://www.cidoc-crm.org/cidoc-crm/> .