As the "Linked Data" meme has gained momentum you've more than likely been on the receiving end of dialog with Linked Open Data community members (myself included) that goes something like this:
"Do you have a URI", "Get yourself a URI", "Give me a de-referencable URI" etc..
And each time, you respond with a URL -- which to the best of your Web knowledge is a bona fide URI. But to your utter confusion you are told: Nah! You gave me a Document URI instead of the URI of a real-world thing or object etc..
Well our everyday use of the Web is an unfortunate conflation of two distinct things, which have Identity: Real World Objects (RWOs) & Address/Location of Documents (Information bearing Resources).
The "Linked Data" meme is about enhancing the Web by unobtrusively reintroducing its core essence: the generic HTTP URI, a vital piece of Web Architecture DNA. Basically, its about so realizing the full capabilities of the Web as a platform for Open Data Identification, Definition, Access, Storage, Representation, Presentation, and Integration.
People, Places, Music, Books, Cars, Ideas, Emotions etc..
A Uniform Resource Identifier. A global identifier mechanism for network addressable data items. Its sole function is Name oriented Identification.
The constituent parts of a URI (from URI Generic Syntax RFC) are depicted below:
A location oriented HTTP scheme based URI. The HTTP scheme introduces a powerful and inherent duality that delivers:
So far so good!
The kind of URI Linked Data aficionados mean when they use the term: URI.
An HTTP URI is an HTTP scheme based URI. Unlike a URL, this kind of HTTP scheme URI is devoid of any Web Location orientation or specificity. Thus, Its inherent duality provides a more powerful level of abstraction. Hence, you can use this form of URI to assign Names/Identifiers to Real World Objects (RWO). Even better, courtesy of the Identity/Address duality of the HTTP scheme, a single URI can deliver the following:
Data about Data. Put differently, data that describes other data in a structured manner.
The predominant model for metadata is the Entity-Attribute-Value + Classes & Relationships model (EAV/CR). A model that's been with us since the inception of modern computing (long before the Web).
The Resource Description Framework (RDF) is a framework for describing Web addressable resources. In a nutshell, its a framework for adding Metadata bearing Information Resources to the current Web. Its comprised of:
The ubiquitous use of the Web is primarily focused on a Linked Mesh of Information bearing Documents. URLs rather than generic HTTP URIs are the prime mechanism for Web tapestry; basically, we use URLs to conduct Information -- which is inherently subjective -- instead of using HTTP URIs to conduct "Raw Data" -- which is inherently objective.
Note: Information is "data in context", it isn't the same thing as "Raw Data". Thus, if we can link to Information via the Web, why shouldn't we be able to do the same for "Raw Data"?
The meme simply provides a set of guidelines (best practices) for producing Web architecture friendly metadata. Meaning: when producing EAV/CR model based metadata, endow Subjects, their Attributes, and Attribute Values (optionally) with HTTP URIs. By doing so, a new level of Link Abstraction on the Web is possible i.e., "Data Item to Data Item" level links (aka hyperdata links). Even better, when you de-reference a RWO hyperdata link you end up with a negotiated representations of its metadata.
Linked Data is ultimately about an HTTP URI for each item in the Data Organization Hierarchy :-)
About this entry:
Author: Kingsley Uyi Idehen
Published: 08/07/2009 14:34 GMT-0500
03/28/2010 12:19 GMT-0500
Comment Status: 2 Comments