Gleaning Resource Descriptions from Dialects of Languages (GRDDL)

Dan Connolly
W3C TAG meeting, 9 Feb 2004
$Revision: 1.7 $ of $Date: 2004/02/24 18:47:50 $ by $Author: connolly $

Talk Overview

Metadata in HTML 1.x (1993)

PICS: Metadata for Decentralized Content Selection (1996)

PICS influence on Semantic Web Architecture

PICS in HTML: Syntax

<!DOCTYPE html ...>
<html lang="en">
  <meta http-equiv="PICS-Labels"
  content='(PICS-1.1 "" l
     by "" on "1996.06.24T10:11-0500"
     exp "1998.06.06T08:00-0500"
     r (n 0 s 0 v 0 l 0))'>
  <meta http-equiv="PICS-Label"
  content='(PICS-1.1 "" l
    by ""
    on "1996.06.24T15:38-0500"
    exp "1998.06.06T08:00-0500"
    r (SS~~000 1))'>

XML for self-similar syntax (1997, 1998)

XML: the one syntax to bind them all... cf section @@ of webarch.

RDF REC anticipates XHTML, XML Schemas (1998)

RDF Core: Just QA, not new design (2001-2004)

Observation: lots of structured data in XHTML dialects (March 2000)

March 2000 design sketch: XSLT for screen-scraping RDF out of real-world data

RDF Users: We need features more than we need standards

Meanwhile, in the TAG...

GRDDL: an 80/20 solution

  1. Pick a way of expressing data in XHTML, and get an XSLT transformation to RDF; for example:
  2. Make links from your XHTML data to the transformation, using the transformation link type:
    <html xmlns="">
      <head profile="">
        <title>Some Document</title>
        <link rel="transformation"
           href="" />
        <meta name="DC.Subject"
           content="ADAM; Simple Search; Index+; prototype" />
  3. Reference the GRDDL profile to make it clear what that transformation link type means:
    <html xmlns="">
      <head profile="">
        <title>Some Document</title>

GRDDL XSLT service demo, example

GRDDL drawback: turing completeness

see: Principle of Least Power. hmm... belongs in webarch somewhere?

GRDDL Syntax: users's choice

GRDDL Semantics: explicit, grounded in the Web

We didn't finish our discussion of URI-based flexibility points before webarch last call. Let's resume, please!

Namespace Documents: RDDL, HyperRDF and GRDDL


turn GRDDL background and Rationale into a TAG finding?