Valuable data for many systems if they could support the wide variety of dialects
Gleaning Resource Descriptions from Dialects of Languages.
A markup for...
... declaring that an XML document includes gleanable data (PROFILE)
... linking to an algorithm (typically XSLT) for gleaning the RDF data from the document (TRANSFORMATION)
The Web 2.0 and the Semantic Web
The Semantic Web is viewed often as heavy, AI-driven ontologies
Where's the data on the Semantic Web?
Microformats are often thought of as a competing alternative to the Semantic Web
hCal
<span class="vevent">
<p><abbr class="dtstart" title="2006-12-05">December 5-</abbr> <abbr class="dtend" title="2006-12-07">7th</abbr>
</b> At <b><span class="summary">;XML 2006</span></b>
(<span class="location">Boston, MA USA</span>)
for a presentation on "Social Semantic Mashups".</span>
We need a community-driven, easy-to-use site for people to
create Semantic Web vocabularies, instead of always going through
W3C Process or just posting them on their site.
Overview of motivating scenarios for Gleaning Resource
Descriptions from Dialects of Languages.
Scheduling
Jane is trying to coordinate a meeting.
Jane is trying to coordinate a meeting with friends. She uses GRDDL to
extract data from each of their calendar pages and combine it in a
single model. She then writes a query to filter the events down to
those dates when all of them are in the same city.
Health Care
Kayode wants to query clinical data.
Kayode uses a single-purpose XML vocabulary as the main representation format for a computer-based
patient record. He uses GRDDL to be able to query these records both in their XML vocabulary
and as RDF, without managing a dual representation.
Aggregating data
Stephan wants a synthetic review before buying a guitar.
Stephan wishes to buy a guitar and visits a site offering a review service.
He uses GRDDL to aggregate reviews and profiles of the reviewers in order
to select the reviews he can trust.
Querying sites and digital libraries
DC4Plus Corp. wants to automate the publication of its electronic documents.
Adeline designs a system to allow here company to streamline the publication of Technical Reports.
The system relies on shared templates for publishing documents and a GRDDL transformation to build
an up-to-date RDF index used to create an authoritative repository.
Wikis and e-learning
The Technical University of Marcilly decided to use wikis to foster knowledge exchanges between lecturers and students.
The Technical University of Marcilly decides to use a wiki with metadata embedded
in its pages to tag, structure, navigate and query the resources of the wiki.
GRDDL is used to extract these metadata as RDF to feed the different tools of the system.
Extracting form descriptions to push entries to Voltaire's blog.
Voltaire has setup a weblog engine that utilizes XForms for editing entries. He also provides a
GRDDL transformation that extracts an RDF description of the XForms that other client applications
can use it to update existing entries using the identified service URIs, and perform other such services.
Validated Documents
the OAI would like to be able to specify document licenses in the schema they share.
The Open Archives Initiative (OAI) publishes an XML schema that universities can use to publish their
archived documents. This schema also identifies a GRDDL transform to apply to all
its instance documents in order to extract their Creative Commons license.
Pulling Data from the Web
Steffen wants to build a directory of the people he works with.
Whenever he gets in touch with someone, Steffen starts a simple script that aims at gathering as
much metadata about this person as possible. Because most of these web pages are not even valid
HTML, the script calls an HTML-tidying tool and if the tidying is complex some of the metadata
is likely to be no longer coherent.
Pushing a transformation
Oceanic Consortium wants to provide transformations for their files without altering them or their schema.
Oceanic wishes to also publish RDF descriptions of their parts reusing the AirPartML documents
produced for an arrangement with a consortium of airlines. The AirPartML schemas are strict and
therefore Oceanic cannot alter their XML documents to specify a transformation.
Yet using the HTTP Headers, Oceanic can specify link and profiles for transformation when
serving their AirPartML documents.
GRDDL technical overview
Overview of some of the technical aspects for Gleaning Resource
Descriptions from Dialects of Languages.
GRDDL enables you to...
... provide an inexpensive set of mechanisms for bootstrapping RDF
content from uniform XML dialects
... shift the burden of formulating RDF away from the author to
transformation algorithms written specifically for XML dialects.
... associate transformations with an individual document either
through direct inclusion of references or indirectly through profile
and namespace documents.
... express and deploy transformations (preferably in XSLT 1.0).
Direct Reference of GRDDL Transformations
GRDDL introduces markup based on existing standards for:
declaring that an XML document includes data compatible with the Resource Description Framework (RDF).
linking to algorithms (typically represented in XSLT), for extracting this data from the document.
The markup includes:
a namespace-qualified attribute for use in general-purpose XML documents.
<book xmlns="http://example.org/book/"
xmlns:grddl='http://www.w3.org/2003/g/data-view#'
grddl:transformation="glean_title.xsl
http://example.org/book/getAuthor.xsl" >
<title>The man who mistook his wife for a hat</title>
...
</book>
In XHTML...
<html xmlns="http://www.w3.org/1999/xhtml">
<head profile="http://www.w3.org/2003/g/data-view" >
<title>The man who mistook his wife for a hat</title>
<link rel="transformation"
href="http://www.w3.org/2000/06/dc-extract/dc-extract.xsl" />
<link rel="transformation" href="glean_title.xsl" />
<meta name="DC.Subject" content="clinical tales" />
...
</head>
...
</html>
Indirect Reference of GRDDL Transformations
XML namespace document (or XHTML profile document)
to declare that every document associated with that namespace (or profile) includes
gleanable data.
<head profile="http://purl.org/NET/erdf/profile">
for linking to an algorithm for gleaning the data.
A namespace document or a profile document also provide a means for their
authors to explain in prose the purpose of the transformation or any policy statements.
Provide a faithful rendition
By specifying a GRDDL transformation, the author of a document states that
the transformation will provide a faithful rendition in RDF of at least
some portion of the information expressed through the XML dialect used
in the source document.
By specifying a GRDDL namespace transformation or profile transformation,
the creator of that namespace or profile states that the transformation will provide a
faithful RDF rendition of a class of source documents which relate to that namespace or
profile.
Example with Microformats
Example referencing GRDDL transformations directly in the head of the HTML.
Example of a calendar in HTML:
2007
Web Design Conference in
Edinburgh, UK:
Jan 8 to
10
Current web pages, written in HTML, contain significant inherent structured data.
RDFa = RDF in attributes to ...
... allow publishers to express this data and structure more completely.
... allow tools to read this data easily.
... allow users to transfer structured data between applications and web sites.
... support a new world of user functionality.
RDFa and microformats
Examples from the RDFa Primer:
An event on a web page can be directly imported into a user's desktop calendar.
A license on a document can be detected so that the user is informed of his rights automatically.
A photo's creator, camera setting information, resolution, and topic can be published at the same time and
as easily as the photo itself, enabling structured search and sharing.
RDFa vs. microformats
when the underlying ontology/vocabulary is simply way too complicated
to be re-expressed in a microformat i.e. microformats are good
for micro-metadata (e.g. name, address, event dates) but not for
complex embedded (e.g. proteins, geological data)
when you need to combine several ontologies/vocabularies in one page
i.e. to handle possible conflicts between primitives
e.g. class="name" and class="name" vs. rel="foaf:name" and rel="prod:name"
HTML Contains Implicit Structure
This document is licensed under a
<a href="http://cc.org/licenses/by/3.0/">
CC License
</a>
and was written by TimBL.
The idea that this implicit structured can be marked up is not new: microformats.
What's new:
consistent syntax,
leveraging all the goodness of RDF,
true mashup-ability of web data.
Basics: Typing a Link
This document is licensed under a
<a href="http://cc.org/licenses/by/3.0/"
xmlns:cc="http://cc.org/ns#" rel="cc:license">
CC License
</a>
and was written by TimBL.
use existing HTML attributes whenever possible: rel.
"Bridging the Clickable and Semantic Webs": there's already a clickable link, now we type it.
self-contained:
copy-and-paste a chunk of HTML along with its RDFa.
build "RDFa wizards" to create copy-and-paste-able content-and-structure.
combine "widgets" on a page, each widget with its own HTML+RDFa (no interference).
More Complex Structure: RDFa goes Deep
This document
...
<div rel="dc:creator" class="foaf:Person"
xmlns:dc="http://..." xmlns:foaf="http://...">
and was written by
<span property="foaf:nickname">
TimBL
</span>.
</div>
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:dc="http://purl.org/dc/elements/1.1/">
<body>
This photo was taken by
<span class="author"
about="photo1.jpg"
property="dc:creator">Mark Birbeck</span>.
</body>
</html>
Rendered:
This photo was taken by
Mark Birbeck.
Add a link to a transformation:
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:dc="http://purl.org/dc/elements/1.1/">
<head profile="http://www.w3.org/2003/g/data-view">
<link rel="transformation"
href="http://www-sop.inria.fr/acacia/soft/RDFa2RDFXML_v_0_8.xsl"/>
</head>
<body>
This photo was taken by <span
class="author" about="photo1.jpg"
property="dc:creator">Mark Birbeck</span>.
</body>
</html>
Don't bury your data in some HTML page: when you publish a document that contains data,
do reference GRDDL profiles and/or transformations for their extraction.
Fabien GANDON,
Fabien.Gandon@sophia.inria.fr
