Creation of Metadata on the Semantic Web

1
Creation of Metadata on the Semantic Web
2
Content

• Overview about creating resources on the WWW.
• Creation of metadata on the Semantic Web
• The language used to express metadata on the
  Semantic Web RDF
• The role of schema in the creation of RDF
• Languages of RDF schema RDFS, OWL
• Obtaining RDF schema from ontology library
  SchemaWeb, Swoogle, DAML ontology library
• Examples of RDF schema RSS 1.0, MusicBrainz,
  Resume, FOAF
• Creation of FOAF file using foaf-a-matic
• Using ontology editor to creating RDF metadata
  protege, OilED
• Making the resulting metadata available on the
  Semantic Web

3
Creation of Resources on WWW

• It is easy to create resources on the WWW.
• Edit html files using a html editor, like MS
  FrontPage, and then upload the resulting html
  files, along with the directory structure, into
  the web server of your web site.

4
Creation of Metadata on the Semantic Web
5
Metadata Language on the Semantic Web

• The Language used to express metadata on the
  Semantic Web RDF

6
RDF MS

• RDF (Resource Description Framework)
• Beyond Machine readable to Machine understandable
• RDF consists of two parts
• RDF Model (a set of triples)
• RDF Syntax (different XML serialization syntaxes)
• RDF Schema for definition of Vocabularies (simple
  Ontologies) for RDF (and in RDF)

7
RDF Data Model

• Resources
• A resource is a thing you talk about (can
  reference)
• Resources have URIs
• RDF definitions are themselves Resources
  (linkage, see requirement 1)
• Properties
• slots, define relationships to other resources or
  atomic values
• Statements
• Resource has Property with Value
• (Values can be resources or atomic XML data)
• Similar to Frame Systems

8
A Simple Example

• Statement
• Ora Lassila is the creator of the resource
  http//www.w3.org/Home/Lassila
• Structure
• Resource (subject) http//www.w3.org/Home/Las
  sila
• Property (predicate) http//www.schema.org/Cre
  ator
• Value (object) "Ora Lassila
• Directed graph

sCreator
http//www.w3.org/Home/Lassila
9
Another Example

• To add properties to Creator, point through an
  intermediate Resource.

http//www.w3.org/Home/Lassila
sCreator
Person//fi/654645635
Email
Name
Ora Lassila
lassila_at_w3.org
10
Example Bag

• The students incourse 6.001 are Amy, Tim,John,
  Mary,and Sue

RdfBag
rdftype
/Students/Amy
students
rdf_1
rdf_2
/Students/Tim
bagid1
rdf_3
/Students/John
rdf_4
/Students/Mary
rdf_5
/Students/Sue
11
Example Alternative

• The source code for X11 may be found at
  ftp.x.org, ftp.cs.purdue.edu, or ftp.eu.net

http//x.org/package/X11
rdfAlt
rdftype
source
altid
rdf_1
ftp.x.org
rdf_2
ftp.cs.purdue.edu
rdf_3
ftp.eu.net
12
RDF schema languages

• RDF Schema
• OWL

13
RDF Schema (RDFS)

• RDF just defines the data model
• Need for definition of vocabularies for the data
  model - an Ontology Language!
• The RDF Schema mechanism provides a basic type
  system for use in RDF models.
• The RDF schema specification language is less
  expressive, but much simpler to implement, than
  full predicate calculus languages such as CycL
  and KIF.

14
Most Important Modeling Primitives

• Core Classes
• Root-Class rdfsResource
• MetaClass rdfsClass
• Literals rdfsLiteral
• rdfssubclassOf-property
• Inherited from RDF properties (slots)
• rdfsdomain rdfsrange
• rdfslabel, rdfscomment, etc.
• Inherited from RDF InstanceOf (rdftype)

15
OWLW3C Web Ontology Language

• OWL provides three increasingly expressive
  sublanguages OWL Lite, OWL DL, and OWL Full.

16
OWLW3C Web Ontology Language
OWL Lite language constructs
RDF Schema Features Class rdfProperty
rdfssubClassOf rdfssubPropertyOf rdfsdomain
rdfsrange Individual
(In)Equality equivalentClass equivalentProperty
sameAs differentFrom allDifferent
Property Characteristics inverseOf
TransitiveProperty SymmetricProperty
FunctionalProperty InverseFunctionalProperty
Property Type Restrictions allValuesFrom
someValuesFrom
Restricted Cardinality minCardinality (only 0
or 1) maxCardinality (only 0 or 1) cardinality
(only 0 or 1)
Header Information ontology imports
17
The role of schema in the creation of RDF

• An XML schema, DTD or XML Schema, used to govern
  the structure of a specific kind of XML document.
• An RDF schema, RDFS or OWL, defines the
  vocabulary of a specific domain.
• In an RDF file, we use name spaces to qualify the
  terms with specific vocabularies.

18
Obtaining RDF schema from ontology library

• SchemaWeb http//www.schemaweb.info/default.aspx
  
• Swoogle http//swoogle.umbc.edu/
• DAML ontology library http//www.daml.org/ontolog
  ies/

19
Examples of RDF schema

• RSS 1.0 http//www.schemaweb.info/schema/SchemaDe
  tails.aspx?id12
• MusicBrainz http//www.schemaweb.info/schema/Sche
  maDetails.aspx?id168
• Resume http//www.schemaweb.info/schema/SchemaDet
  ails.aspx?id89
• FOAF http//www.schemaweb.info/schema/SchemaDetai
  ls.aspx?id29

20
Creation of metadata using specific tool

• Creation of FOAF file using foaf-a-matic
• http//www.ldodds.com/foaf/foaf-a-matic.html

21
Creation of metadata using general tool

• Using ontology editors to create RDF metadata
• protege http//protege.stanford.edu/
• OilED http//oiled.man.ac.uk/
• SWOOP http//www.mindswap.org/2004/SWOOP/

22
Making the resulting metadata available on the
Semantic Web

• Upload the resulting metadata files to web
  server.
• Using special file name for google to find it.
• E.g., foaf.rdf
• Use the metadata link in the head of home page.
• Publish into public registry.