Glossary · Semantic interoperability and information models
Namespace
Also known as: Name space
German: Namensraum
In information technology, a namespace is a context, usually identified by a URI, within which names or identifiers are unique, so that the same name can be used in different namespaces without conflict. OPC UA, XML and RDF use namespaces to separate models from different organizations.
- Information models
In one sentence
A namespace is a context, often identified by a URI, within which names are unique, so the same name can be reused elsewhere without conflict.
Example
In an OPC UA server, the node Temperature from the machine builder's namespace and the node Temperature from a companion specification are distinct nodes.
How it applies
- Engineering: In OPC UA, each information model has a namespace URI; within a server, nodes are addressed by a namespace index that maps to that URI. Clients should resolve the URI rather than hard-code the index, since indexes can differ between servers.
- Integration: Organizations should use namespace URIs under a domain they control and version them consistently.
- Documentation: When documenting interfaces, give the namespace URI together with node identifiers or element names, so that integrators can find the right definitions.
Namespace URI vs. namespace index
The namespace URI is the globally unique name of the namespace. The namespace index in OPC UA is a local number assigned by a server for efficiency. The URI is stable across servers; the index is not.