Glossary · Semantic interoperability and information models
Uniform Resource Identifier (URI)
Also known as: URI
German: Uniform Resource Identifier (URI)
A Uniform Resource Identifier (URI) is a compact string of characters that identifies a resource according to the generic syntax of RFC 3986, consisting of a scheme followed by scheme-specific parts, for example https://example.com/docs or urn:uuid:…. URLs, which also locate a resource, and URNs, which name it, are kinds of URI.
- Information models
- Standards
In one sentence
A URI is a string that identifies a resource using a scheme-based syntax defined in RFC 3986; URLs and URNs are kinds of URI.
Example
An OPC UA information model uses the namespace URI of its publisher, and an AAS uses a URI as the global identifier of each asset.
How it applies
- Engineering: URIs identify namespaces in OPC UA and XML, resources in RDF, and assets in the AAS. Use URIs under a domain your organization controls, and keep them stable.
- Integration: A URI need not be resolvable, but resolvable HTTP URIs that return useful information make integration easier.
- Documentation: Documentation uses URIs for links, identification links on products and metadata vocabularies. Changing URIs breaks references in documents, QR codes and systems, so plan them for the product's lifetime.
URI vs. IRI
A URI is limited to a subset of ASCII characters. An IRI (Internationalized Resource Identifier) extends the URI syntax to Unicode, so that identifiers can contain characters from other scripts. Every URI is also an IRI; an IRI can be converted to a URI by percent-encoding.