Case Study: News Syndication at W3C

W3C Communications Team knows HTML well; picked up XHTML quickly
RSS emerged as a syndication mechanism
W3C's news content management system is just CVS; no database
But by adding just a class attribute here and a rel attribute there, we get enough structure to transform it to RSS using XSLT

Site Summaries in XHTML is a cost-effective way to formalize our news metadata.

GRDDL Details

In addition to structured XHTML, add the profile URI:

<html xmlns="http://www.w3.org/1999/xhtml">
<head profile="http://www.w3.org/2000/08/w3c-synd/#">
  ...
</head>
<body>
  ...
<div id="x200501110b" class="item">
<h3><img alt="" width="17" height="11" src="/Icons/right" />Policy for
Authorized W3C Translations Announced</h3>

<p><span class="date">2005-11-10:</span> W3C is pleased to announce...

The w3c-synd profile links to home2rss.xsl, which produces:

...
<item rdf:about="http://www.w3.org/News/2005#item158">
<title>Policy for Authorized W3C Translations Announced</title>
<description>2005-11-10: W3C is pleased to announce ...

GRDDL Syntax: author's choice

works with DTD-happy XHTML
via a link with rel="transformation", qualified by the GRDDL profile
works with XML in general
via grdd:transformation attribute on the root element
the link refers to a transformation, typically XSLT, that maps to RDF/XML
the link may be indirect via a profile or namespace document

GRDDL Semantics: explicit, grounded in the Web

Screen scraping: at your own risk
GRDDL: author explicitly agrees to data extraction algorithm
profile grounds the dialect in URI space
output of transformation is expressed in RDF, using URIs for property names

A person (or a machine) can "follow your nose" from the document to the transformation algorithm, to the data, to the definitions of the terms used in the data.

SQL * URIs = SPARQL

Use GRDDL to aggregate data from friends etc, then...

  PREFIX foaf: <http://xmlns.com/foaf/0.1/>
  PREFIX c: <http://www.w3.org/2002/12/cal/icaltzd#>
  SELECT ?name, ?summary, ?when
   FROM <myFriendsBlogsData>
   WHERE { ?somebody foaf:name ?name; foaf:mbox ?mbox.
           ?event c:summary ?summary;
                  c:dtstart ?ymd;
                  c:attendee [ c:calAddress ?mbox ]
         }.

?name	?summary	?when
Tantek Çelik	Web 2.0	2005-10-05
Norm Walsh	XML 2005	2005-11-13
Dan Connolly	W3C tech plenary	2006-02-27

See SPARQL Query Language for RDF W3C Working Draft Feb 2006, plus Norm's travel last year

Consistency checking

Modelling assumption: on a given day, a person can only be in one city

PersonDay a owl:Class; s:subClassOf k:Entity;
 s:subClassOf [ owl:onProperty _city; owl:maxCardinality 1 ].

Then run pellet, an OWL consistency checker:

java -jar pellet.jar -inputFile ,mash.rdf -unsat
Input file: ,mash.rdf
OWL Species: Full
DL Expressivity: ALCHIF(D)
Consistent: No
Reason: There is an anonymous individual X, identified by
  this path (file:...cal/mash/calbg#oct6
      http://www.cyc.com/2004/06/04/cyc#temporallyIntersects X),
  which has more than 1 values for property file:...cal/mash/calbg#_city
  violating the cardinality restriction
Time: 8784 ms (Loading: 6485 Preprocessing: 0
   Species Validation: 2202 Consistency: 96 )

In other words: You can't be two places at once!

For details: see Semantic Web Data Integration with hCalendar and GRDDL, given Nov 2005 at XML 2005 in Atlanta

Tabulator: a Semantic Web browser

alpha version

More Use Cases

DAWG membership, SPARQL issues and comment status
pubrules checker, TR automation
list of W3C groups and activities
Embedded RDF, hCalendar on my home page
hCard, hCalendar for my list of past talks, trips, and events
PAW group meeting minutes, cwm dev agenda

Wish List

my kids' soccer schedules
wikipedia infoboxes
aa.com flight itineraries
I generate my own from their text format and flightCal.py: aa-nce itin
Conference papers:
see XHTML for computer science research papers and bibliographies, 2005-11-03

Summary

hCalendar is not too much to ask of authors
GRDDL makes it authorized Semantic Web data
other dialects work too: RSS, geoURL, Embedded RDF, RDF/A
Semantic Web data:
- merges easily
- can be queried with SPARQL
- can be checked for consistency with OWL reasoners

Acknowledgements, Colophon

These slides: http://www.w3.org/2003/g/talk62/slides

Dog-food: view source for...
- hCalendar
- hCard
- GRDDL
written using nxml-mode
CSS/javascript presentation magic is Slidey
References
- Gleaning Resource Descriptions from Dialects of Languages (GRDDL), Hazaël-Massieux and Connolly May 2005
- SPARQL Query Language for RDF W3C Working Draft Feb 2006
- RDF Calendar - an application of the Resource Description Framework to iCalendar Data, Connolly and Miller September 2005

Practical Semantic Web Deployment with Microformats and GRDDL