Web Services and the Semantic Web: The AI past, the IR future
1.
Web
Services and the Semantic Web:
The AI past, the IR future
Henry S. Thompson
School of Informatics
University of Edinburgh,
Markup Technology Ltd.
and
World
Wide Web Consortium
2.
Web
Services-Semantic Web
Web Services is the name for a
marketing initiative
- The technology has been scrambling to catch
up and provide some grounding for the phrase ever since it was
invented
The Semantic Web is the name for a
vision of the future
- Originally Tim Berners-Lee's attempt to
answer the question: What is the full potential of the (World Wide)
Web?
They have a common
dependency
3.
Web
Services
My quick summary of Web
Services:
- Loosely-coupled distributed
applications
Three key aspects:
- Messages-XMLP (ex-SOAP), XML
Schema
- Definition-WSDL: XML->XML function
signatures
- Discovery-UDDI (CORBA, oops)
4.
Semantic
Web
Just as XML is SGML specialised for the
WWW
You can think about the Semantic Web as
UML for the WWW
Initially (RDF) just a simple
relation-triple model of assertions about resources
- Serialised as XML
- With a few bells and whistles for collections
and reflection
Starting to grow
5.
The Origins of
the Semantic Web
The information retrieval
crisis beginning in the late 1990s led to a widespread interest in
what has come to be called metadata.
What is metadata?
- It's just data.
- But it's data about other
data
- Data intended for machine
consumption
What could metadata do for
us?
- Give search engines something to work
with (relational triples) that is designed for their
needs.
- Give us all a place to record what a
document, or any other resource, is for or
about.
6.
First
Requirements for Metadata
What would we need to make this
work?
- A standard syntax, so metadata can be
recognised as such;
- One or more standard vocabularies, so search
engines, producers and consumers all speak the same
language;
- Lots of resources with metadata
attached;
- Attribution and trust
- Is this resource really about Pamela
Anderson?
7.
Meaning is at
the Core
Both SW and WS depend crucially on
moving beyond syntax
- XML as such is just ASCII for the
21st century
- Web-appropriate
linearisation
- for tree-structured documents with
internal links
- and tree-structured documents are a pretty
good transfer syntax for just about anything
- What prospects for moving beyond syntax to
semantics?
- The Semantic Web is committed by its very
name
- Web Services can't succeed without
it
- And this is where the relevance of history
kicks in
8.
Web Services and
the GRID
Services and resources are not
electrons
- And computers 'looking' for 'service
providers' are not the same as human beings shopping on the
web
So the metaphors underlying
both WS and the GRID can be very misleading
Negotiation between producers
and consumers is the key
- If you can't describe what you want,
you can't have it
- If you can't describe what you've got,
no-one will use it
- If you can't dicker, you'll always
lose
These observations apply
equally well to Web Services and the GRID
9.
Those Who do not
Study History
are doomed to repeat it
The history of AI is full of examples
of two weaknesses:
- Over-promising by insiders
- 'AI Winter'; Intelligent Agents
- Over-optimism by outsiders
25 years ago Ed Feigenbaum described
Terry Winograd's work as "a breakthrough in enthusiasm"
- I worry that WS and SW, in their reliance on
effective computational semantics, are vulnerable to the same
criticism
10.
The History of
the Knowledge Representation Problem
The representation and
exploitation of knowledge has been the ultimate grand challenge for
Artificial Intelligence since its inception
Our own human intelligence has
sometimes been a real handicap
- It's too easy to look at a screenshot
and see how much knowledge is captured
(#$and
(#$isa ?x #$Person)
(#$feelsEmotion ?x #$Fear #$High))
Designing apparently
expressive notations is easy
- Making them do actual work is
much harder
11.
The Missing
Inference Engine
What we learned in 1978--79 was
that designing an approach to KR without first designing an
inference engine was a waste of time
Actually worse than a waste of
time
- Because you could invest a lot
of work in representing stuff
- And still end up with nothing to show
for it
So we were left with an
embarrassing tradeoff:
- Use (something isomorphic to)
1st-order predicate logic, and get a variety of pretty
well-understood inference engines
- Use something more user-friendly and
expressive, but be unable to exploit it
This tradeoff is still with us
today
12.
How is a KR
System like a Piano?
The title of a 1980 Special Issue of
SIGART
- The end of the beginning, with
hindsight
KRL, Semantic Nets, KL-ONE, . .
.
Where are they now?
- Learned the lesson of the missing engine the
hard way
CYC was the last and biggest
failure
CYC was the grandparent of
RDF
- So RDF has some ground to make up
13.
The Semantic Web
Today
1 ½ of the four first
requirements for metadata I mentioned earlier:
- RDF Model and Syntax gives us recognisable
metadata
- OWL gives us a mechanism for
defining shared vocabularies, and we have a few
14.
The Semantic Web
Tomorrow
Reworking the syntax and cleaning up
the model
Starting serious work on Rule, Logic
and Trust
Involving probabilistic/statistical
processing
15.
Making the
connection
Most SemWeb enthusiasts are
where the AI community was 30 years ago
- The Web as knowledge resource can
deliver exact answers
Just the beginnings of the
next step in the parallel
- The Web as the basis for probably
nearly correct answers
Karen Sparck Jones's work is headed for a
new lease on life!