URI Scheme for RDF namespaces – management aspects

[jechterhoff]

Description

In #2 we propose the following URI scheme for INSPIRE RDF vocabularies: http://inspire.ec.europa.eu/ont/{app-schema-code}. The following management-related aspects are open for discussion:

• Should the namespace end with a slash ("/") or hash (#")?
• We have excluded version information (see, for example, http://xmlns.com/foaf/spec/#sec-evolution for a reasoning to exclude version information in the namespace URI).

  Discussion Item

Which management aspects must be considered for the selected URI scheme?

• Are there good reasons to include a version number in the RDF namespace?
• Should a “hash namespace” or a “slash namespace” be used?

[jechterhoff]

Version information can be added to an ontology, using the version IRI (available in OWL2) and the versionInfo (available since OWL 1). In an ontology series, the annotation properties owl:backwardCompatibleWith and owl:incompatibleWith can be used to indicate backwards compatibility (or the lack thereof). Therefore, even if the ontology namespace does not include version information itself, subsequent versions of the ontology do not necessarily need to be backwards compatible.

[jechterhoff]

We decided to go with hash namespaces to identify ontology components. The reasons behind that decision are:

• The expressions and axioms that comprise an INSPIRE ontology are often used together. In some cases there can be complex dependencies between concepts. Hash URIs ensure that a client receives all relevant information about these dependencies when it accesses the ontology.
• An ontology that is contained in a single document can easily be published.
• If a client recognizes that a specific term is defined by a hash URI, then it can download the ontology from this URI, cache it, and re-use it whenever another term with the same base URI is accessed. In other words, hash URIs support caching, and can thus reduce the number of HTTP round-trips and reduce access latency. The sice of the ontology document should be reasonably small, since it only contains the ontology components derived from one particular INSPIRE application schema.
• A slash URI can still be used for individuals, i.e. RDF resources that have an INSPIRE RDF/OWL class as type.