|
It seems to be best practice to group related resources in common namespaces, for instance all resources with URI reference starting with Which semantic Web technologies rely on the character sequence of URI references apart from equality checks? In theory two URI references are either equal or not but not comparable in any other way such as substring patterns, aren't they? If this is true, where is this rule violated in practice? |
No, they don't carry any formal semantics, except for human readers.
For computer programmes, it wouldn't make any difference. But human readable identifiers are as much important as choosing human readable names for programme variables. They help people understanding what the content is about. Certainly, the end user will never see the names of the variables or the URIs of things, but there are always various people manipulating the raw data behind the application interfaces.
The actual sequence is used by protocoles if you ever want to dereference the URIs.
You MAY use substring comparison for various reasons, one of which is to check that URIs are following best practices, e.g., by using the same namespace for terms of the same ontology. But whatever the practice, good or bad, you should'nt draw conclusions on the meaning of those URIs. 1
Apparently (http://answers.semanticweb.com/questions/130/how-do-i-build-a-triple-store @ROWLEX Admin 's answer) Intellidimension uses MD5 hashes of URIs in their triplestore to enhance performance. |
|
Its worth reading the RFC for uri's since it describes the syntax and semantics: http://www.ietf.org/rfc/rfc3986.txt FYI, a UUID can be a URN and hence a URI. The benefit of using a HTTP uri is that it is generally resolvable (or should be resolvable) to a dereferenceable URI - i.e one where you can get a representation of the thing being identified. |
|
When you say "semantics" I guess it is open to interpretation. The URI string does not have an effective semantics on a standard RDF/RDFS/OWL/SPARQL level, no. But I would argue that there is a whole standard dedicated to providing URIs with semantics (in combination with HTTP, which, for URIs, is kind of analogous to the interpretations used in RDF/OWL semantics): Architecture of the World Wide Web, Volume One. Some example semantics associated with the syntax of a URI:
These semantics are specific to the URI string itself and feed directly into Linked Data guidelines and best practices.
Roughly speaking, anything that uses HTTP. Other non-trivial uses include systems that examine the authority of URIs when dealing with Web data; as a quick example: Using naming authority to rank data and ontologies for web search. A Harth, S Kinsella, S Decker. ISWC 2009. 1
Yes, you're right, "semantics" is open to interpretation and I hope my answer is not too much directed to a way of interpreting it. I +1'ed you answer ... I guess it really depends on what the OP means by "semantics". Ironically. :) |
Do have a look at Linked Data patterns at http://patterns.dataincubator.org/book/. The Identifier Patterns chapter will give you some ideas on how to create URIs and why they suggest that way. Hope that helps