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The Semantic Web
What are feeds and how do I
use them?
The Meaning of RSS
- RSS might stand for "Rich
Site Summary," "RDF Site Summary," "Really Simple Syndication,"
or something else, depending upon your point of view. The two
major variants include an RDF-based specification (RSS version
0.9, 1.0) and a non-RDF XML specification (RSS versions 0.91,
0.92, 0.93, 0.94, 2.0). From the version 1.0 specification
abstract: "RDF Site Summary (RSS) is a lightweight multipurpose
extensible metadata description and syndication format. RSS is
an XML application, conforms to the W3C's RDF Specification and
is extensible via XML-namespace and/or RDF based
modularization." From the IETF Internet-Draft
'draft-nottingham-rss-media-type-00': "RSS is a lightweight,
multipurpose, extensible metadata description and syndication
format. RSS is an XML application. RSS is currently used for a
number of applications, including news and other headline
syndication, weblog syndication, and the propogation of software
update lists. It is generally used for any situation when a
machine-readable list of textual items and/or metadata about
them needs to be distributed. There are a number of revisions of
the RSS format defined, many of which are actively used..."
The Semantic Web
- This RDF grammar gives
meaning to resources, and will eventually give us what Tim
Berners-Lee calls the "Semantic Web." This is a utopian Web with
metadata and meaning attached to content so machines can process
it, and not just for display purposes but for various
applications. If the semanticians have their way, autonomous
software agents will make your plane reservations, search
engines will become more relevant, and the Web as a whole will
become much more usable. We talked to Dan Libby about his
original unreleased "futures" RSS document, and his vision for
RSS:
WR: The "futures"
document, tell us more about that, was that your first version
of RSS?
DL: Yes. That was what I proposed as 0.9. By that time, I had
been in several talks with Guha, who was championing RDF at
Netscape, and he had gotten me in touch briefly with Eric Miller
and Dan Brickley, so they both had a chance to review it.
Of course, then it had to be approved by the marketing folks at
Netcenter, and they wanted a simpler format that could easily be
read/written by hand and that was less error prone. 0.9 was the
next proposal, as a compromise, and it was accepted. So it is
still valid RDF, but it is not as useful for an RDF aggregration
database.WR: Your "futures" document appears remarkably similar
to RSS 1.0, as it uses Dublin Core, rdf:Seq(uences) of items. Is
RSS 1.0 close to what you had in mind from the start?
DL: Yes. The format itself is close, though I still haven't seen
the types of applications that I was envisioning. I thought that
if someone were to combine a real RDF database (e.g. Guha's
rdfdDB) with thousands of RSS site
descriptions, that it would open the door to truly powerful
filtering. Think if every site and every news organization
published RSS feeds and then other sites aggregated them and
allowed users to setup news filters the way your mail client
lets you setup mail filters. Each of these highly customized
filters could be called an "agent." For example, suppose I'm
interested in XML-RPC, PHP and tennis. I could setup filters
that search across all the aggregated news sources and present
me with the things I'm interested in, regardless of source.
Thus, we shift away from today's provider-centric model to a
user-interest-centric model.
WR: What about aggregators like Meerkat and My Userland?
DL: I think they are both on the right track, but (to my
knowledge) neither has packaged it up with the sort of filtering
and user-centric or "agent" mechanism that I'm talking about.
NewsIsFree still uses the concept of a "box," which represents a
single RSS channel. I had hoped to move past this in My
Netscape, but was never given the chance. I want to see a "my"
page that is truly about my interests, regardless of source. I
don't care if "Gardening Daily" published the RSS article, I
still want to see it. Of course, I would still like to have the
option of adding a channel by provider, but it should not be the
only method available.
Further, because there is not yet any sort of Universal RDF
Descriptions repository, it is difficult for providers to tag
data with meaningful shared metadata. For example, if I want to
use dc:subject to tag an article as belonging to
"politics/libertarian/anarcho-capitalism," I can, but you (the
receiver) won't necessarily know what that is, or have any means
of finding out, because we don't have a shared classification
system. Instead, I'd like to be able to point the dc:subject at
a URI that represents "politics/libertarian/anarcho-capitalism"
in a shared taxonomy.
WR: What are the advantages of RDF?
DL: As I see it, RDF enables computers to agree on a common
description for complex things (see
http://swag.semanticweb.org/, an
effort to create a common language for the Semantic Web). Let's
suppose we are talking about people. If an article were tagged
with the keywords "President Bush," you would assume it refers
to George W. Bush, the current president. A computer would have
no way of distinguishing between George W. and his father, and
it certainly couldn't tell you anything interesting about
either. If instead, it were tagged with "http://taxonomy.rdf.org/people/usa/presidents/#52,"
there would be no ambiguity. If both my filter (above) and the
RSS feed provided this URI, then there would be an exact match,
and I would see the article. Otherwise, it might fall back to a
keyword search.
It also enables one to define meaningful links between such
objects. Thus, as I'm creating my filter, I would really be
surfing through a multi-dimensional graph. When I come across
the node representing George Bush, I can click on the
"predecessor" link to find "Bill Clinton," or the "father" link
to find "George Bush, Sr." Any relationships anyone has ever
created to or from this "President Bush" are instantly
accessible.
A more down to earth benefit of using RDF is the ability to
reuse existing RDF vocabularies, such as Dublin Core. So there
is greater interoperability, and we are using existing building
blocks rather than reinventing the wheel.
Yet another is the flexibility that is gained by using XML
namespaces together with the RSS modules concept to allow users
to easily expand the RSS vocabulary, and to maintain backwards
compatibility.
What are feeds and how do I
use them?
- A feed is a regularly updated summary of web
content, along with links to full versions of that content. When
you subscribe to a given website's feed by using a feed reader,
you'll receive a summary of new content from that website.
Important: you must use a feed reader in order to subscribe to
website feeds. When you click on an RSS or Atom feed link, your
browser may display a page of unformatted gobbledygook.
What are RSS and Atom?
RSS and Atom are the two feed formats. Most feed readers support
both formats. Right now, Google News supports Atom 0.3 and RSS
2.0.
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