Providing and discovering definitions of URIs by Jonathan A. Rees.
Abstract:
The specification governing Uniform Resource Identifiers (URIs) [rfc3986] allows URIs to mean anything at all, and this unbounded flexibility is exploited in a variety contexts, notably the Semantic Web and Linked Data. To use a URI to mean something, an agent (a) selects a URI, (b) provides a definition of the URI in a manner that permits discovery by agents who encounter the URI, and (c) uses the URI. Subsequently other agents may not only understand the URI (by discovering and consulting the definition) but may also use the URI themselves.
A few widely known methods are in use to help agents provide and discover URI definitions, including RDF fragment identifier resolution and the HTTP 303 redirect. Difficulties in using these methods have led to a search for new methods that are easier to deploy, and perform better, than the established ones. However, some of the proposed methods introduce new problems, such as incompatible changes to the way metadata is written. This report brings together in one place information on current and proposed practices, with analysis of benefits and shortcomings of each.
The purpose of this report is not to make recommendations but rather to initiate a discussion that might lead to consensus on the use of current and/or new methods.
The criteria for success:
- Simple. Having too many options or too many things to remember makes discovery fragile and impedes uptake.
- Easy to deploy on Web hosting services. Uptake of linked data depends on the technology being accessible to as many Web publishers as possible, so should not require control over Web server behavior that is not provided by typical hosting services.
- Easy to deploy using existing Web client stacks. Discovery should employ a widely deployed network protocol in order to avoid the need to deploy new protocol stacks.
- Efficient. Accessing a definition should require at most one network round trip, and definitions should be cacheable.
- Browser-friendly. It should be possible to configure a URI that has a discoverable definition so that ‘browsing’ to it yields information useful to a human.
- Compatible with Web architecture. A URI should have a single agreed meaning globally, whether it’s used as a protocol element, hyperlink, or name.
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I had to look it up to get the page number but I remembered Karl Wiegers in Software Requirements saying:
Feasible
It must be possible to implement each requirement within the known capabilities and limitations of the system and its environment.
The single agreed meaning globally, whether it’s used as a protocol element, hyperlink, or name requirement is not feasible. It will stymie this project, despite the array of talent on hand, until it is no longer a requirement.
Need proof? Name one URI with a single agreed meaning globally, whether it’s used as a protocol element, hyperlink, or name.
Not one that the W3C TAG, or TBL or anyone else thinks/wants/prays has a single agree meaning globally, … but one that in fact has such a global meaning.
It’s been more than ten years. Let’s drop the last requirement and let the rather talented group working on this come up with a solution that meets the other five (5) requirements.
It won’t be a universal solution but then neither is the WWW.
How about http://www.example.com?
Comment by shunting — June 30, 2011 @ 11:25 am
No, because a non-English speaker who first sees http://www.example.com has no reason to think that URL is different from any other URL.
Too often we argue English tokens are just opaque tokens, but that really isn’t true, at least not to English speakers. If that were true, so many IT tokens would not resemble English words. Yes?
Comment by Patrick Durusau — June 30, 2011 @ 1:44 pm
Suppose http://www.example.com is more like a logo than a word; a sequence of shapes rather than a sequence of characters. Wouldn’t it still perform its technical function that way, and yet still have a…. have a…
Well, how do we know that we’ve ever succeeded in achieving “a single agreed meaning globally”? What’s the operational test?
* * *
On another note, got yer semantic web right here:
http://hashtags.org/tag/bittorrent/
Ha.
Comment by shunting — July 1, 2011 @ 8:52 am