Publishers of data need to be able to handle the various situations in which URIs do not deliver metadata about the resource.
The discussion on the issue is available here.
A recurring issue for Linked Data implementation is that URIs are required as values for properties that link to resources.
Various collections of URIs have been minted that are being used as the values for such properties. However, resolving these URIs does not always deliver information about the things these URIs represent.
Resolving such URIs should deliver metadata about the resource. Unfortunately, this is not always the case, and if it is the case there are two types of responses to a HTTP GET on the URI. In any case, an organisation that mints URIs should strive to keep the delay between minting URIs and resolving them as short as possible.
Resolving such URIs should deliver metadata about the resource. Unfortunately, this is not always the case, and if it is the case there are two types of responses to a HTTP GET on the URI.
Clients need to be able to handle these various situations which may not always be straightforward.
The example is based on the Nobel Prize catalogue, which is available via http://www.nobelprize.org/datasets/dcat. Some modifications were made in order to clarify the guideline.
First case (no response): data.europa.eu/3rx/EUProgramme/ contains information about that particular URI.
Second case (response): https://www.w3.org/ns/org#Organization contains information about the URI combined with information about other URIs
A related issue is that the resolution of URIs should be maintained over time. As soon as URIs are made public, they will be included in metadata that will rely on persistent resolution.
Organisations that mint URI must define a persistence policy for their URIs.
The European Commission has established a persistent URI policy and resolution service at http://data.europa.eu/ that aims to persistently resolve all URIs that are minted for resources maintained by the European Commission. The EU URI policy has the following characteristics: governance, URI pattern, URI redirection, service level guarantees.