1. Shelley Powers, O’Reilly SNU IDB Lab. Hyewon Kim
Practical RDF Chapter 5. Important Concepts from the W3C RDF Vocabulary/Schema
Shelley Powers, O’Reilly
SNU IDB Lab.
Hyewon Kim

2. Outline Introduction RDF Vocabulary: Describing the Data
Core RDF Schema Elements
Refining RDF Vocabularies with Constraints
RDF Schema Alternatives

3. Introduction RDF (Resource Description Framework) specification
Syntax specification
How RDF constructs relate to each other
How they can be diagrammed in XML
Schema specification
A ruled-based dictionary that defines the elements of importance to a domain
Describes how these elements relate to one another

4. RDF Vocabulary: Describing the Data
Metadata – data about data
Same specification can be used with many different domain
Concept of metadata’s role
Relational database
Store many different types of data by using metadata structures

5. RDF Vocabulary: Describing the Data Metadata’s Role in Existing Applications (1/3)
Example
Change the domain and the domain-specific storage constructs become pretty useless
CUSTOMER PK
CUSTOMER_ID
ORDER PK
ORDER_ID
CUSTOMER_ORDER
PK,FK1
PK,FK2
CUSTOMER ID
ORDER_ID

6. Multiple uses of the same storage mechanism for different domains
RDF Vocabulary: Describing the Data Metadata’s Role in Existing Applications (2/3)
Multiple uses of the same storage mechanism for different domains
Relational database schema defines below
Database tables
Primary and foreign key
Columns
Provide a domain-neutral description of information
Schema table
Schema column
Table 1
Table 2
Table 3 ….
customer
order
Customer_order
table
Col name1
Col name2
Col name3 ….
Order
data
count …
customer
name
Address

7. Same syntax for web resource
RDF Vocabulary: Describing the Data Metadata’s Role in Existing Applications (3/3)
Same syntax for web resource
Don’t store information about a web resource in a domain-specific XML element called WEB_PAGE
Store it on an rdf:Description element and use RDF to define the properties for this new resource

8. RDF Vocabulary: Describing the Data RDF Schema: Metadata Repository
Provides the same functionality as the relational database schema
Provides the resources necessary to describe the objects and properties of a domain-specific schema
Vocabulary
It describes
Objects
Attributes
Relationships within a specific area of interest

9. Core RDF Schema Elements
Marked by a specific namespace
xmlns:rdfs = “

10. Core RDF Schema Elements Overview of the RDF Schema classes (1/6)
All resources within RDF are implicitly members of this class
rdfs:Resource
Type or category of resource
rdfs:Class
Literals within RDF documents, such as text strings
rdfs:Literal
Literals with RDf documents that use XML syntax
rdfs:XMLLiteral
Superclass of all container classes
rdfs:Container
Members of containers
rdfs:Container MembershipProperty
Data typing information
rdfs:Datatype

11. Core RDF Schema Elements Overview of the RDF Schema classes (2/6)
rdfs:Resource & rdfs:Class
Every resource within an RDF document has a common ancestor class : rdf:resource
All new resource types are identified by an rdfs:Class statement, including the rdfs:Resource element itself
<? Xml version=“1.0”?>
<rdf:RDF
xmlns:rdf=“
xmlns:pstcn=“
<rdf:Descriptoin rdf:about=“
<pstcn:author>Shelley Powers></pstcn:author>
<pstcn:title>Architeuthis Dux</pstcn:title>
<rdf:Description>
</rdf:RDF>
Schema
<rdfs:Class rdf:ID=“Article”>
<rdfs:subClassOf rdf:resource=“
</rdfs:Class>

12. Core RDF Schema Elements Overview of the RDF Schema classes (3/6)
rdfs:Container
Superclass of all RDF container elements
rdf:Bag
rdf:Seg
rdf:Alt
rdfs:ContainerMembershipProperty
Resource is a member of a container
_1, _2, _3 and so on

13. Core RDF Schema Elements Overview of the RDF Schema classes (4/6)
rdfs:Datatype
Class of all data types
Subclass of rdfs:Literal
rdfs:XMLLiteral
Allows to embed XML into the RDF/XML document
Instance of rdfs:Datatype
Class of all XML literals

14. Core RDF Schema Elements Overview of the RDF Schema classes (5/6)
A few RDF classes
Cross the boundary between the metalanguage and instances of the same
Include as member all reified RDF statements
rdf:Statement
Used to group members
rdf:Bag, rdf:Seq, rdf:Alt
Has members all RDF lists
rdf:List
Define the attributes that, in turn, describe the resource
rdf:Property

15. Core RDF Schema Elements Overview of the RDF Schema classes (6/6)
RDF Schema for Article
<? Xml version=“1.0”?>
<rdf:RDF
xmlns:rdf=“
xmlns:rdfs=“
xmlns:pstcn=“
<rdfs:Class rdf:about=“
<rdfs:subClassOf rdf:resource=“
</rdfs:Class>
<rdf:Property rdf:about=“
<rdfs:domain rdf:resource= />
</rdf:Property>
<rdf:Property rdf:about=“
</rdf:RDF>

16. RDF specification’s purpose RDF Schema specification’s purpose
Core RDF Schema Elements Demonstrations of the RDF Schema Properties (1/10)
Demonstrations of the RDF Schema Properties
RDF specification’s purpose
Define resource and associated facts
Provide a way to allow these resource/fact mappings to interact
RDF Schema specification’s purpose
Statement about each resource
Individual properties
Only difference between two
One is instance of business data (such as Article)
The other is metadata ( related to the RDF model)

17. Core properties (from both the RDF and RDFS namespaces ) of RDF Schema
Core RDF Schema Elements Demonstrations of the RDF Schema Properties (2/10)
Core properties (from both the RDF and RDFS namespaces ) of RDF Schema
rdfs:subClassOf
rdfs:seeAlso
rdfs:member
rdfs:label
rdf:subject
rdf:object
rdf:rest
rdfs:range
rdfs:subPropertyOf
rdfs:isDefinedBy
rdfs:comment
rdf:type
rdf:predicate
rdf:first
rdfs:domain
rdf:value

18. Core RDF Schema Elements Demonstrations of the RDF Schema Properties (3/10)
rdfs:subClassOf
Identify a class that is a subclass of another
<rdfs:Class rdf:ID=“WebPage”>
rdfs:subClassOf rdf:resource=“ />
</rdfs:Class>
<rdfs:Class rdf:ID=“Article”>
rdfs:subClassOf rdf:resource=“ />

19. Core RDF Schema Elements Demonstrations of the RDF Schema Properties (4/10)
rdfs:subPropertyOf
<? Xml version=“1.0”?>
<rdf:RDF
xmlns:rdf=“
xmlns:rdfs=“
xmlns:pstcn=“
<rdfs:Class rdf:about=“
<rdfs:subClassOf rdf:resource=“
</rdfs:Class>
<rdf:Property rdf:about=“
<rdfs:domain rdf:resource= />
</rdf:Property>
<rdf:Property rdf:about=“
<rdf:Property rdf:about=“
<rdfs:domain rdf:resource=“ />
<rdfs:subPropertyOf rdf:resource=“ />
<rdf:Property rdf:about=“
</rdf:Property>/rdf:RDF>

20. Core RDF Schema Elements Demonstrations of the RDF Schema Properties (5/10)
rdfs:seeAlso
Another resource contains additional information
<rdfs:Class rdf:about=“ >
<rdfs:subClassOf rdf:resource=“ />
</rdfs:Class>
<rdfs:Class rdf:about=“ >
<rdfs:subClassOf rdf:resource= />
<rdfs:seeAlso rdf:resource=“ />

21. Core RDF Schema Elements Demonstrations of the RDF Schema Properties (6/10)
rdfs:isDefinedBy
Identify the namespace for the resource
<rdfs:Class rdf:about=" >
<rdfs:isDefinedBy rdf:resource=“ />
<rdfs:label xml:lang=“en”>Statement</rdfs:label>
<rdfs:subClassOf rdf:resource=“ />
<rdfs:comment>The class of RDF statement.</rdfs:comment>
</rdfs:Class>
<rdfs:Class rdf:about=" >
<rdfs:isDefinedBy rdf:resource=“ />
<rdfs:label xml:lang=“en”>Literal</rdfs:label>
<rdfs:comment>This represents the set of atomic values, eg. Textual string</rdfs:comment>
</rdfs:Class>

22. Core RDF Schema Elements Demonstrations of the RDF Schema Properties (7/10)
rdfs:member
Superproperty for each numbered container element
_1, _2, and so on
rdfs:comment
Provide human readability to an RDF model
Provide documentation of resources
rdfs:label
Provide a readable version of the resource’s name
Can attach xml:lang

23. RDF Schema documentation elements
Core RDF Schema Elements Demonstrations of the RDF Schema Properties (8/10)
RDF Schema documentation elements
<? xml version=“1.0”?>
<rdf:RDF
xmlns:rdf=“
xmlns:rdfs=“
xmlns:pstcn=“
<rdfs:Class rdf:about=“
<rdfs:subClassOf rdf:resource=“
<rdfs:comment>Unique Online article</rdfs:comment>
<rdfs:label xml:lang=“en”>Article</rdfs:label>
</rdfs:Class>
<rdf:Property rdf:about=“
<rdf:type rdf:resource=“ />
<rdfs:domain rdf:resource=“ />
<rdfs:comment>Online Article Title</rdfs:comment>
</rdf:Property>
<rdf:Property rdf:about=“
<rdfs:comment>Primary author of article</rdfs:comment>
<rdfs:label xml:lang=“en”>Author</rdfs:label>
</rdf:RDF>

24. Core RDF Schema Elements Demonstrations of the RDF Schema Properties (9/10)
rdf:type
Define the type of resources
Usually assumed and is not explicitly given
<rdfs:Property rdf:about=“ >
<rdfs:domain rdf:resource= />
<rdfs:comment>Primary author of article</rdfs:comment>
<rdfs:label xml:lang=“en”>Author</rdfs:label>
<rdf:type rdf:resource=“ />
</rdfs:Property>

25. rdf:subject, rdf:predicate, rdf:object
Core RDF Schema Elements Demonstrations of the RDF Schema Properties (10/10)
rdf:subject, rdf:predicate, rdf:object
Used with reification to explicitly define an RDF statement
rdf:first, rdf:rest
Explicitly define the relationships within a collection

26. Refining RDF Vocabularies with Constraints (1/2)
rdfs:domain
Associate a property with the resource
An RDF property can be used for more than one resource type
<? Xml version=“1.0”?>
<rdf:RDF
xmlns:rdf=“
xmlns:rdfs=“
xmlns:pstcn=“
<rdfs:Class rdf:about=“
<rdfs:subClassOf rdf:resource=“
<rdfs:comment>Unique Online article</rdfs:comment>
<rdfs:label xml:lang=“en”>Article</rdfs:label>
</rdfs:Class>
<rdf:Property rdf:about=“
<rdf:type rdf:resource= />
<rdfs:domain rdf:resource=“ />
<rdfs:comment>Online Article Title</rdfs:comment>
</rdf:Property>
<rdf:Property rdf:about=“
<rdfs:comment>Primary author of article</rdfs:comment>
<rdfs:label xml:lang=“en”>Author</rdfs:label>
</rdf:RDF>

27. Refining RDF Vocabularies with Constraints (2/2)
rdfs:range
Only one RDF range constraint can be attached to any property
Can use a master class for a property (more than one data type)
<? Xml version=“1.0”?>
<rdf:RDF
xmlns:rdf=“
xmlns:rdfs=“
xmlns:pstcn=“
<rdfs:Class rdf:about=“
<rdfs:subClassOf rdf:resource=“
</rdfs:Class>
<rdf:Class rdf:about=“
<rdf:subClassOf rdf:resource=“ />
</rdf:Class>
<rdf:Class rdf:about=“
<rdf:Class rdf:about=“
<rdf:subClassOf rdf:resource=“ />
<rdf:Property rdf:about=“
<rdf:domain rdf:resource=“ />
<rdf:range rdf:resource= />
</rdf:Property>
</rdf:RDF>
range
domain
WebPage
Directory
Article
Example

28. RDF Schema Alternatives (1/3)
DTD(Document Type Declarations) & XML Schema
<!ELEMENT Items(item*)
<!ELEMENT item(productName, quantity, USPrice, comment? shipDate?)>
<!ATTLIST item partNum CDATA #REQUIRED>
<!ELEMENT productName (#PCDATA)>
<!ELEMENT quantity (#PCDATA)>
<!ELEMENT USPrice(#PCDATA)>
<!ELEMENT comment(#PCDATA)>
<!ELEMENT shipDate(#PCDATA)>

29. RDF Schema Alternatives (2/3)
DTD(Document Type Declarations) & XML Schema
<xsd:element name=“Items”>
<xsd:complexType name=“items”>
<xsd:sequence>
<xsd:element name=“item” minOccurs=“0” maxOccurs=“unbounded”>
<xsd:complexType>
<xsd:element name=“productName” type=“xsd:string”/>
<xsd:element name=“quantity”>
<simpleType>
<xsd:restriction base=“xsd:positiveInteger”>
<xsd:maxExclusive value=“100”/>
<xsd:restriction>
</xsd:simpleType>
</xsd:element>
<xsd:element name=“USPrice” type=“xsd:decimal”/>
<xsd:element name=“comment” minOccurs=“0”/>
<xsd:element name=“shipDate” type=“xsd:date” minOccurs=“0”/>
</xsd:sequence>
<xsd:attribute name=“partNum” type=“SKU” use=“required” />
</complexType>
</xsd:complxType>

30. RDF Schema Alternatives (3/3)
RELAX NG Compact Syntax
Combination of DTD readability and W3C XML Schema data typing
Items = element Items {item*}
Item = element item {att.partNum, productName, quantity, USPrice, comment?, shipDate? }
att.partNum = attribute partNum {text}
productName = element productName {text}
Quantity = element quantity {xsd:positiveInteger {maxExclusive=“100”}}
USPrice = element USPrice {xsd:decimal}
Comment = element comment {text}
shipDate = element shipDate {xsd:date}
Start = Items