06-10-2012, 01:08 PM
Semantic Web
Semantic Web.ppt (Size: 1.48 MB / Downloads: 61)
History of the Semantic Web
Web was “invented” by Tim Berners-Lee (amongst others), a physicist working at CERN
TBL’s original vision of the Web was much more ambitious than the reality of the existing (syntactic) Web:
“... a goal of the Web was that, if the interaction between person and hypertext could be so intuitive that the machine-readable information space gave an accurate representation of the state of people's thoughts, interactions, and work patterns, then machine analysis could become a very powerful management tool, seeing patterns in our work and facilitating our working together through the typical problems which beset the management of large organizations.”
The Syntactic Web is…
A hypermedia, a digital library
A library of documents called (web pages) interconnected by a hypermedia of links
A database, an application platform
A common portal to applications accessible through web pages, and presenting their results as web pages
A platform for multimedia
BBC Radio 4 anywhere in the world! Terminator 3 trailers!
A naming scheme
Unique identity for those documents
Hard Work using the Syntactic Web…
Complex queries involving background knowledge
Find information about “animals that use sonar but are not either bats, dolphins or whales”
Locating information in data repositories
Travel enquiries
Prices of goods and services
Results of human genome experiments
Delegating complex tasks to web “agents”
Book me a holiday next weekend somewhere warm, not too far away, and where they speak French or English
XML is a first step
Semantic markup
HTML layout
XML meaning
Metadata
within documents, not across documents
prescriptive, not descriptive
No commitment on vocabulary and modelling primitives
RDF is the next step
Resource Description Framework (RDF)
A standard of W3C
Relationships between documents
Consisting of triples or sentences:
<subject, property, verb>
<Tolkien, wrote, The Lord of the Rings>
RDFS extends RDF with standard “ontology vocabulary”:
Class, Property
Type, subClassOf
domain, range
RDF and RDFS
RDFS defines the ontology
classes and their properties and relationships
what concepts do we want to reason about and how are they related
there are authors, and authors write books
RDF defines the instances of these classes and their properties
Mark Twain is an author
Mark Twain wrote “Adventures of Tom Sawyer”
“Adventures of Tom Sawyer” is a book
Notation: RDF(S) = RDF + RDFS