|
|
|
|
|
|
RDF is used to specify semantics for data
expressed in XML in a standardized, interoperable manner |
|
RDF is a simple frame language |
|
Data is described in relational sentences using
binary relations |
|
Classes and relations are defined in schema |
|
Classes are organized in subclass hierarchies |
|
Domain and range constraints on relations are
supported |
|
Provides interoperability between applications
that exchange machine-understandable information on the Web |
|
|
|
|
|
|
Resource |
|
Object in the domain of discourse |
|
E.g., Web page, portion of Web page, Web site |
|
Denoted by resource identifier (i.e., object
constant) |
|
Property |
|
Binary relation in the domain of discourse |
|
Used to describe a resource |
|
Relates resources to other resources or to literals
(constants) |
|
Statement |
|
Relational sentence: (Property Subject Object) |
|
I.e., a slot value |
|
Subject: a resource |
|
Object: resource identifier or XML primitive
data type |
|
|
|
|
|
|
|
|
Ora Lassila is the creator of the resource
http://www.w3.org/Lassila. |
|
RDF Statement: |
|
Subject:
http://www.w3.org/Lassila |
|
Property:
Creator |
|
Object:
“Ora Lassila” |
|
KIF equivalent: |
|
(Creator http://www.w3.org/Lassila “Ora Lassila”) |
|
|
|
|
|
|
|
Description |
|
Group of statements about the same resource
(I.e., a frame) |
|
RDF element |
|
Wrapper that marks the boundaries in an XML
document of content intended to be mappable into a set of RDF statements |
|
Syntax:
RDF ::= ‘<RDF’ attributeSpec* ‘>’ |
|
descriptionElement* ‘</RDF>’ |
|
Description element |
|
Identifies the resource being described |
|
Syntax: |
|
description ::= ‘<rdf:Description’
idAboutAttr? ‘>’ |
|
propertyElement* ‘</rdf:Description>’ |
|
idAboutAttr ::= idAttr | aboutAttr |
|
aboutAttr ::= ‘about=“’ URI-reference ‘”’ |
|
idAttr ::= ‘ID= “’ IDsymbol ‘”’ |
|
|
|
|
|
|
Property element |
|
A property-value pair corresponding to an RDF
statement |
|
Syntax |
|
propertyElement ::= ‘<’ propName ‘>’ value
‘</’ propName ‘>’ | |
|
‘<’ propName resourceAttr ‘/>’ |
|
value ::= description | string |
|
resourceAttr ::= ‘resource=“’ URI-reference ‘”’ |
|
Example description |
|
Ora Lassila is the creator of the resource
http://www.w3.org/Lassila |
|
<RDF xmlns =
"http://www.w3.org/1999/02/22-rdf-syntax-ns#" |
|
xmlns:s = "http://description.org/schema/"> |
|
<Description about = "http://www.w3.org/Lassila"> |
|
<s:Creator> Ora Lassila </s:Creator> |
|
</Description> |
|
</RDF> |
|
|
|
|
|
“Ora Lassila is the creator of the resource
http://www.w3.org/Lassila.” |
|
RDF Description: |
|
<RDF xmlns =
"http://www.w3.org/1999/02/22-rdf-syntax-ns#" |
|
xmlns:s = "http://description.org/schema/"> |
|
<Description about="http://www.w3.org/Lassila"> |
|
<s:Creator> Ora Lassila </s:Creator> |
|
</Description> |
|
</RDF> |
|
OKBC equivalent: |
|
http://www.w3.org/Lassila |
|
Creator:
“Ora Lassila” |
|
RDF Statement: |
|
Subject:
http://www.w3.org/Lassila |
|
Property:
Creator |
|
Object:
"Ora Lassila” |
|
|
|
|
<RDF xmlns:dc =
"http://purl.org/metadata/dublin_core#"> |
|
<Description about = "http://www.dlib.org"> |
|
<dc:Title> D-Lib Program </dc:Title> |
|
<dc:Description> The D-Lib program … </dc:Description> |
|
<dc:Publisher> Corporation For National …
</dc:Publisher> |
|
<dc:Date> 1995-01-07 </dc:Date> |
|
<dc:Subject> |
|
<Bag> <li> Research; statistical methods </rdf:li> |
|
<li> Education, research, related topics </rdf:li> |
|
<li> Library use Studies </rdf:li> |
|
</Bag> |
|
</dc:Subject> |
|
<dc:Type> World Wide Web Home Page </dc:Type> |
|
<dc:Format> text/html </dc:Format> |
|
<dc:Language> en </dc:Language> |
|
</Description> |
|
</RDF> |
|
|
|
|
http://www.dlib.org |
|
Title: “D-Lib Program” |
|
Description: “The D-Lib program …” |
|
Publisher: “Corporation For National …” |
|
Date: “1995-01-07” |
|
Subject: (listof “Research; statistical methods” |
|
“Education, research, related
topics” |
|
“Library use Studies”) |
|
Type: “World Wide Web Home Page” |
|
Format: “text/html” |
|
Language: “en” |
|
|
|
|
|
|
Classes |
|
Resource |
|
Property |
|
Class |
|
Literal |
|
Statement |
|
Container |
|
Bag |
|
Seq |
|
Alt |
|
ContainerMembershipProperty |
|
Properties |
|
type |
|
subject |
|
predicate |
|
object |
|
value |
|
_1, _2, _3, … |
|
|
|
|
|
Resource |
|
Documentation: “The class of all objects.” |
|
Instance-Of: Class |
|
Disjoint-Decomposition: (listof Class Property) |
|
Class |
|
Documentation: “The class of all classes.” |
|
Subclass-Of: Resource |
|
Instance-Of: Class |
|
Property |
|
Documentation: “The class of all properties.” |
|
Subclass-Of: Resource |
|
Instance-Of: Class |
|
type |
|
Documentation: “Class membership property.” |
|
Instance-Of: Property |
|
|
|
|
|
|
An ontology added to RDF |
|
Classes [2] |
|
ConstraintResource |
|
ConstraintProperty |
|
Properties [8] |
|
subClassOf |
|
subPropertyOf |
|
seeAlso |
|
isDefinedBy |
|
comment |
|
label |
|
range |
|
domain |
|
|
|
|
|
subClassOf |
|
Documentation: “The subset/superset relation
between classes.” |
|
Instance-Of: Property |
|
subPropertyOf |
|
Documentation: “Specifies that one property is a
specialization of another.” |
|
Instance-Of: Property |
|
seeAlso |
|
Documentation: “Specifies a resource that
contains information about the subject resource.” |
|
Instance-Of: Property |
|
isDefinedBy |
|
Documentation: “Specifies the resource defining
the subject resource.” |
|
Instance-Of: Property |
|
subPropertyOf: seeAlso |
|
|
|
|
|
Resource |
|
Documentation: “The class of all objects.” |
|
type: Class |
|
Disjoint-Decomposition: (listof Class Property) |
|
Class |
|
Documentation: “The class of all classes.” |
|
subClassOf: Resource |
|
type: Class |
|
Property |
|
Documentation: “The class of all properties.” |
|
subClassOf: Resource |
|
type: Class |
|
|
|
|
|
|
|
<rdf:Description ID = "MotorVehicle"> |
|
<rdf:type resource =
“http://www.w3.org/PR-rdf-schema-19990303#Class” /> |
|
<rdfs:subClassOf rdf:resource =
“http.../PR-rdf-schema-19990303#Resource” /> |
|
</rdf:Description> |
|
<rdf:Description ID = "PassengerVehicle"> |
|
<rdf:type resource =
“http://www.w3.org/PR-rdf-schema-19990303#Class” /> |
|
<rdfs:subClassOf rdf:resource= “#MotorVehicle” /> |
|
</rdf:Description> |
|
<rdf:Description ID = "biologicalParent"> |
|
<rdf:type resource =
“http://www.w3.org/1999/02/22-rdf-syntax-ns#Property” /> |
|
</rdf:Description> |
|
<rdf:Description ID = "biologicalFather"> |
|
<rdf:type resource =
“http://www.w3.org/1999/02/22-rdf-syntax-ns#Property” /> |
|
<rdfs:subPropertyOf rdf:resource = “#biologicalParent” /> |
|
</rdf:Description> |
|
|
|
|
|
A class name can be used as an element name |
|
Example property definition: |
|
<rdf:Description ID =
"biologicalParent"> |
|
<rdf:type resource =
"www.w3.org/1999/02/22-rdf-syntax-ns#Property"/> |
|
</rdf:Description> |
|
can be written as: |
|
<rdf:Property ID = “biologicalParent” /> |
|
Example class definition: |
|
<rdf:Description ID = "MotorVehicle"> |
|
<rdf:type resource =
“http://www.w3.org/PR-rdf-schema-19990303#Class” /> |
|
<rdfs:subClassOf rdf:resource =
“http.../PR-rdf-schema-19990303#Resource” /> |
|
</rdf:Description> |
|
can be written as: |
|
<rdf:Class ID = "MotorVehicle"> |
|
<rdfs:subClassOf rdf:resource =
“http.../PR-rdf-schema-19990303#Resource” /> |
|
</rdf:Class> |
|
|
|
|
<rdf:Class ID="MotorVehicle"> |
|
<rdfs:subClassOf
rdf:resource="http.../PR-rdf-schema-19990303#Resource"/> |
|
</rdf:Class> |
|
<rdf:Class ID="PassengerVehicle"> |
|
<rdfs:subClassOf rdf:resource="#MotorVehicle"/> |
|
</rdf:Class> |
|
<rdf:Class ID="Van"> |
|
<rdfs:subClassOf rdf:resource="#MotorVehicle"/> |
|
</rdf:Class> |
|
<rdf:Class ID="MiniVan"> |
|
<rdfs:subClassOf rdf:resource="#Van"/> |
|
<rdfs:subClassOf rdf:resource="#PassengerVehicle"/> |
|
</rdf:Class> |
|
|
|
|
|
Domain and range specification on properties |
|
Examples: |
|
<rdf:Description ID = "registeredTo"> |
|
<rdf:type resource = “www.w3.org/ … rdf-syntax-ns#Property” /> |
|
<rdfs:domain rdf:resource = “#MotorVehicle” /> |
|
<rdfs:range rdf:resource = “#Person” /> |
|
</rdf:Description> |
|
<rdf:Description ID = "rearSeatLegRoom"> |
|
<rdf:type resource = “www.w3.org/ … rdf-syntax-ns#Property” /> |
|
<rdfs:domain rdf:resource = “#PassengerVehicle” /> |
|
<rdfs:domain rdf:resource = “#Minivan” /> |
|
<rdfs:range rdf:resource = “www.w3.org/datatypes#Number” /> |
|
</rdf:Description> |
|
|
|
|
<rdf:RDF xmlns:rdf =
"www.w3.org/1999/02/22-rdf-syntax-ns#" |
|
xmlns:rdfs =
"//www.w3.org/TR/1999/PR-rdf-schema-19990303#"> |
|
<rdfs:Class rdf:ID = "Person"> |
|
<rdfs:comment> The class of people. </rdfs:comment> |
|
<rdfs:subClassOf rdf:resource = |
|
“www.classtypes.org/useful_classes#Animal” /> |
|
</rdfs:Class> |
|
<rdf:Property ID = "maritalStatus"> |
|
<rdfs:range rdf:resource = “#MaritalStatus” /> |
|
<rdfs:domain rdf:resource = “#Person” /> |
|
</rdf:Property> |
|
|
|
|
<rdf:Property ID = "ssn"> |
|
<rdfs:comment> Social Security Number </rdfs:comment> |
|
<rdfs:range rdf:resource = |
|
“http://www.datatypes.org/useful_types#Integer” /> |
|
<rdfs:domain rdf:resource = “#Person” /> |
|
</rdf:Property> |
|
<rdf:Property ID = "age"> |
|
<rdfs:range rdf:resource = |
|
“http://www.datatypes.org/useful_types#Integer” /> |
|
<rdfs:domain rdf:resource = “#Person” /> |
|
</rdf:Property> |
|
|
|
|
<rdfs:Class rdf:ID = “MaritalStatus” /> |
|
<MaritalStatus rdf:ID = “Married” /> |
|
<MaritalStatus rdf:ID = “Divorced” /> |
|
<MaritalStatus rdf:ID = “Single” /> |
|
<MaritalStatus rdf:ID = “Widowed” /> |
|
|
|
</rdf:RDF> |
|
|
|
|
|
|
Severely lacking in expressive power |
|
Domain and range constraints rather than
Value-Type |
|
E.g., can’t define class of people all of whose
children are male |
|
No cardinality constraints |
|
Particularly important for “exactly 1” and “at
most 1” |
|
No decompositions |
|
Particularly important for “disjoint” and
“exhaustive” |
|
No axioms |
|
No negation (!) |
|
Not useful for checking consistency |
|
E.g., can’t prove an object is not an instance
of a class |
|
Basically a typing system |
|
Does provide identifiers for objects |
|
Enables referencing and describing |
|
Notes