As per usual I am writing this post with the aim of killing a
number of meme-birds with a single post in relation
to the emerging Linked Data Web.
*On* the ubiquitous Web of "Linked Documents", HREF means (by
definition and usage): Hypertext Reference to an HTTP accessible Data
Object of Type: "Document" (an information resource). Of course we don't
make the formal connection of Object Type when dealing with the
Web on a
daily basis, but whenever you encounter the "resource not found"
condition notice the message: HTTP/1.0 404 Object Not Found, from the
Server tasked with retrieving and returning the resource.
*In* the Web of "Linked Data", a complimentary addition to
the current Web of "Linked Documents", HREF is used to reference
Data Objects that
are of a variety of "Types", not just "Documents". And the way this
is achieved, is by using Data Object Identifiers (URIs / IRIs that are
generated by the Linked Data
deployment platform) in the strict sense i.e. Data Identity
(URI) is separated from Data Address
(URL). Thus, you can reference a Person Data
Object (aka an instance of a Person Class) in your HREF and the
HTTP Server returns a Description of the
Data Object via a Document (again, an information
resource). A document containing the Description of a Data Object
typically contains HREFs to other Data Objects that expose the
Attributes and Relationships of the initial Person Data Object, and
it this collection of Data Objects that is technically called a
"Graph" -- which is what RDF models.
What I describe above is basic stuff for anyone that's
familiar with Object Database or Distributed Objects technology and
The Linked Document Web is a collection of physical resources
that traverse the Web Information Bus in palatable format i.e
documents. Thus, Document Object Identity and Document Object Data
Address can be the same thing i.e. a URL can serve as the ID/URI of a Document Data Object.
The Linked Data Web on the other hand, is a Distributed Object
Database, and each Data Object must be uniquely defined, otherwise
we introduce ambiguity that ultimately taints the Database itself
(making incomprehensible to reasoning challenged machines). Thus we
must have unique Object IDs (URIs / IRIs) for People, Places,
Events, and other things that aren't Documents. Once we follow the
time tested rules of Identity, People can then be associated with
the things they create (blog posts, web pages, bookmarks,
wikiwords etc). RDF
is about expressing these graph model relationships while RDF
serialization formats enables the information resources to
transport these data object link ladden information resources to
requesting User Agents.
Put in more succinct terms, all documents on the Web are
compound documents in reality (e.g. mast contain a least an image
these days). The Linked Data Web is about a Web where Data Object
IDs (URIs) enable us to distill source data from the information
contained in a compound document.
The degree of unobtrusiveness of new technology, concepts, or
new applications of existing technology, is what ultimately
determines eventual uptake and meme virulence (network
effects). For a while, the Semantic Web meme was mired in confusion and
general misunderstanding due to a shortage of practical use case
The emergence of the SPARQL Query Language has provided critical
infrastructure for a number of products, projects, and demos, that
now make the utility of the Semantic Web vision
mush clearly via the simplicity of Linked Data, as exemplified by
About this entry:
Author: Kingsley Uyi Idehen
Published: 03/12/2008 16:08 GMT-0500
Modified: 04/10/2008 16:13 GMT-0500
Tags: webservices , rdf , xml , semanticweb , web30 , foaf , sparql , socialnetworking , openlink , virtuoso , DataSpace
Categories: Demos , Virtual Database , SQL , Semantic Web , Web Services (Web 2.0)
Comment Status: 0
This document is empty and basically useless. It is generated by a web service that can make some statements in HTML+Microdata format.
This time the service made zero such statements, sorry.