Open Standards Guide to Semantic Web Languages

Open Standards for the
Semantic Web
XML / RDF(S) / OWL / SOAP

© 2004 Pieter De Leenheer

Data About ...
<?xml version=quot;1.0quot;?>
<rdf:RDF xmlns:rdf=quot;http://www.w3.org/1999/02/22-rdf-syntax-ns#quot;>
xmlns:dc=quot;http://purl.org/dc/elements/1.1/quot;>
<rdf:Description rdf:about= quot;http://www.starlab.vub.ac.be/
staff/pdeleenheer/teaching/infosys/XML_RDF_RDFS_OWL_SOAP.pdf”>
<dc:title>XML / RDF / RDFS / OWL / SOAP</dc:title>
<dc:creator>Pieter De Leenheer </dc:creator>
<dc:coverage>Informatiesystemen</dc:coverage>
<dc:subject>
<rdf:Bag>
<rdf:li>XML</rdf:li>
<rdf:li>RDF</rdf:li>
<rdf:li>RDFS</rdf:li>
<rdf:li>OWL</rdf:li>
<rdf:li>SOAP</rdf:li>
</rdf:Bag>
</dc:subject>
</rdf:Description>
</rdf:RDF>

Lecture Outline today
• Once upon a time there was XML

• W3C Open Standards Compliance

• Resource Description Framework (RDF)

• RDF versus XML

• RDF Schema (RDFS)

• RDF triples versus DOGMA lexons

• Simple Object Access Protocol

• Online RDF services and tools

• RDFS Shortcomings: Web Ontology Language

Lecture outline next
week

• RDFS Semantics
• Web Ontology Language
• Description Logics

eXtensible Markup Language
• XML is a meta- language
• XML stands for EXtensible Markup Language
• XML is a markup language much like HTML
• XML was designed to describe data
• XML tags are not predefined. You must define
your own tags
• XML uses a Document Type Definition (DTD)
or an XML Schema to describe the data
• XML with a DTD or XML Schema is designed
to be self-descriptive

XML Speciﬁcation

<?xml version=“1.0”?>
<medicine-inventory>
<medicine name=“asperin”>
<author>Felix Hoffmann</author>
<patent-date>1889/03/06/</patent-date>
</medicine>
</medicine-inventory>

XML Spec: XML declaration
</medicine>
The XML version and the
</medicine-inventory> character encoding used in the
document. In this case the document
conforms to the 1.0 specification of XML
and uses the ISO-8859-1 (Latin-1/West
European) character set.

XML Spec: root element
</medicine> The root element of the
document: this Document describes
(or is) a medicine inventory

XML Spec: child elements
</medicine>
Data of medicine

medicine has attribute with value: name = “asperin”

A child element: medicine

XML Spec: tags (1)
</medicine>
</medicine-inventory> Data of medicine

Begin tag of an element
End tag of an element

XML Spec: tags (2)
</medicine>

Data of author

Begin tag of an element End tag of an element

W3C Consortium
• Vendor-independent
• three host institutions (MIT/LCS in the USA, ERCIM
headquarters in France, and Keio University in
Japan).
• Standardisation by recommendation
• Goals:
• Universal Access: To make the Web accessible to all by
promoting technologies that take into account the vast
differences in culture, languages, education, ability, material
resources, access devices, and physical limitations of users on
all continents;
• Semantic Web: To develop a software environment that permits
each user to make the best use of the resources available on the
Web;
• Web of Trust: To guide the Web's development with careful
consideration for the novel legal, commercial, and social issues
raised by this technology.
• Open source

Standards and Procedures

■
■ ■
SOAP
CSS XHTML
■
■ ■
SPARQL
CGI XHTML+Voice
■
■ ■
SMIL
DOM XML
■
■ ■
SRGS
GRDDL XML Events
■
■ ■
SSML
HTML XML Information Set
■
■ ■
VoiceXML
OWL XML Schema
■
■ ■
WCAG
P3P XPath
■
■ ■
WSDL
RDF XQuery 1. Working Draft (WD)
■
■ ■
XACML
SVG XSLT
2. Last Call Working Draft
■
■ XForms
SISR
3. Candidate Recommendation


(CR)
4. Proposed Recommendation
(PR)
5. W3C Recommendation (REC)

Resource Description Framework
• RDF is not a language but a model
• RDF is written in XML
• RDF is a W3C standard
• RDF is for describing resources on the web
• RDF is designed to be read by computers
• RDF is not designed for being displayed to people
• RDF uses URIs to identify web resources
• RDF uses property values to describe web resources
• RDF uses the terms resources, properties, and values
• RDF also uses the terms subject, predicates and
objects

RDF: introducing example
<rdf:RDF xmlns:rdf=quot;http://www.w3.org/1999/02/22-rdf-syntax-ns#quot;

xmlns:cd=quot;http://www.recshop.fake/cd#quot;>
<rdf:Description rdf:about=quot;http://www.recshop.fake/cd/Empire
Burlesquequot;>
<cd:artist>Bob Dylan</cd:artist>
<cd:country>USA</cd:country>
<cd:company>Columbia</cd:company>
<cd:price>10.90</cd:price>
<cd:year>1985</cd:year>
</rdf:Description>

<rdf:Description rdf:about=quot;http://www.recshop.fake/cd/Hide
your heartquot;>
<cd:artist>Bonnie Tyler</cd:artist>
<cd:country>UK</cd:country>
<cd:company>CBS Records</cd:company>
<cd:price>9.90</cd:price>
<cd:year>1988</cd:year>
</rdf:Description>
</rdf:RDF>

RDF building block
“STARLab” is the title of the website http://starlab.vub.ac.be
• Subject (Resource) - http://starlab.vub.ac.be
• Predicate (Property) – title
• Object (Literal) – “STARLab”

2 RDF statements
“STARLab” is the title of the website http://
starlab.vub.ac.be, and is created by “Peter Spyns”
• Predicate (Property) – title
• Object (Literal) – “STARLab”

• Predicate (Property) – creator
• Object (Literal) – “Peter Spyns”

17

Nested RDF statements
Peter Spyns, whose phone is 4571 is the creator of the
website http://starlab.vub.ac.be which has title
“STARLab”.

RDF basic serialisation syntax
The RDF root element and namespace:


.
.
.
</rdf:RDF>

RDF Description
Attributes
 about – refers to a URI of an existing resource
 ID – signals the creation of a new resource (see later)

<rdf:Description rdf:about=quot;http://starlab.vub.ac.bequot;>
.
.
.
</rdf:Description>
</rdf:RDF>

RDF Property (1)
 Property names must be associated with a
schema
 Qualify property names with namespace prefix
 Value – description element or string

<dc:title>STARLab</dc:title>
<dc:creator>Peter Spyns</dc:creator>
.
.
.
</rdf:Description>
</rdf:RDF>

RDF Property (2)
 Property names must be associated with a
schema
 Qualify property names with namespace prefix
 Value – description element or string

<dc:creator>
<rdf:Description>
<dc:name>Peter Spyns</dc:name>
<dc:phone>4571</dc:phone>
</rdf:Description>
</dc:creator>
</rdf:Description>
</rdf:RDF>

Marking value types

<dc:alsoContains rdf:parseType=“Literal”>
<h1>STARLab Official Homepage</h1>
</dc:alsoContains>
</rdf:Description>
</rdf:RDF>

XML formatted value

Marking value types (2)

<dc:lastUpdate>18</dc:lastUpdate>
<dc:creator rdf:parseType=quot;Resourcequot;>
</dc:creator>
</rdf:Description>
</rdf:RDF> <dc:creator>
<rdf:Description>
</rdf:Description>
</dc:creator> 24

Introducing structure in the data
Last update of the site was 18 months, days, years
ago ????

<dc:creator>
<rdf:Description>
</rdf:Description>
</dc:creator>
</rdf:Description>
</rdf:RDF>

Introducing structure in the data (2)
Candidate solution (I) causes a decoding problem:


<dc:lastUpdate>18 days</dc:lastUpdate>
<dc:creator>
<rdf:Description>
</rdf:Description>
</dc:creator>
</rdf:Description>
</rdf:RDF>

Candidate solution (II) refines the syntax, but ‘18’
and ‘days’ are not related:

<dc:lastUpdateUnit>days</dc:lastUpdateUnit>
<dc:creator>
<rdf:Description>
</rdf:Description>
</dc:creator>
</rdf:Description>
</rdf:RDF>

Candidate solution (III) introduces rdf:value field:
the processor is signaled that the data itself is
in this field  accepted as solution !

<dc:lastUpdate rdf:parseType=“Resource”>
<rdf:value>18</rdf:value>
<dc:lastUpdateUnit>days</dc:lastUpdateUnit>
</dc:lastUpdate>
...
</rdf:RDF>

RDF vs. XML
<E1>
<E1>
<E2>
<E2>
<E3>
<URIref to E3>
...
</E2>
<E3>
</E1>
</E2>
</E1>
<E3>
...
</E3> In RDF, the tree structure can be
broken down and distributed: this has
advantageous consequences...
30

RDF vs. XML (2)
RDF XML
• Needs to be cached
• Lazy loading, less
fully before use
memory strain
• Comparable to
• Comparable to foreign
bilocation in
keys in relational DBs
hierarchical DBs
• Data from disparate
• Nesting
docs can be joined
(important Semantic Web
asset)

Properties as Resources
Breaking the nesting !

<dc:creator rdf:resource=quot;http://starlab.vub.ac.be/staff/pspynsquot; />
</rdf:Description>

<rdf:Description rdf:about=quot;http://starlab.vub.ac.be/staff/pspynsquot;>
</rdf:Description>
</rdf:RDF>

Properties as Resources
<dc:creator>Peter Spyns</dc:creator>
<dc:date>2001-04-10</dc:date>
<dc:format>text/html</dc:format>
<dc:language>en</dc:language>
</rdf:Description>
</rdf:RDF>

<rdf:Description rdf:about=quot;http://starlab.vub.ac.bequot;
dc:title=quot;STARLabquot; dc:creator=quot;Peter Spynsquot; dc:date=quot;2001-04-10quot;
dc:format=quot;text/htmlquot; dc:language=quot;enquot;
/>
</rdf:RDF>

Abbreviated RDF
xmlns:dc=quot;http://purl.org/dc/elements/1.1/quot;
<rdf:Description about=quot;http://starlab.vub.ac.bequot;>
<dc:creator>
<rdf:Description about=quot;http://starlab.vub.ac.be/staff/pspynsquot;>
</rdf:Description>
</dc:creator>
</rdf:Description>
</rdf:RDF>

<rdf:Description about=quot;http://starlab.vub.ac.bequot;>
<dc:creator rdf:resource=quot;http://starlab.vub.ac.be/staff/pspynsquot;
dc:name=quot;Peter Spynsquot;
dc:phone=quot;4571quot;/>
</rdf:Description>
</rdf:RDF>

Abbreviated RDF (2)
<dc:creator>
<rdf:Description>
</rdf:Description>
</dc:creator>
</rdf:Description>
</rdf:RDF>

<dc:creator rdf:parseType=quot;Resourcequot;>
</dc:creator>
</rdf:Description>
</rdf:RDF>

Abbreviated RDF (3)
http://starlab.vub.ac.be/staff/pdeleenheer is an instance of type Webpage...
<rdf:Description about=quot;http://starlab.vub.ac.be/staff/pdeleenheerquot;>
<rdf:type rdf:resource=quot;http://www.schemas.org/www/Webpagequot;/>
<dc:creator>Pieter De Leenheer</dc:creator>
<dc:title>Pierre’s Page</dc:title>
</rdf:Description>
</rdf:RDF>

xmlns:s=quot;http://www.schemas.org/www/quot;>
<s:WebPage about=quot;http://starlab.vub.ac.be/staff/pdeleenheerquot;>
</s:WebPage>
</rdf:RDF>

RDF Containers
• Bag - an unordered list of resources or
literals
• Sequence - an ordered list of resources
or literals
• Alternative - a list of resources or literals
that represent alternatives for the value of
a property

rdf:Bag
Some user-defined namespace
(see later)

xmlns:cd=quot;http://www.recshop.fake/cdquot;>

<rdf:Description rdf:about=quot;http://www.recshop.fake/cd/Beatles_For_Salequot;>
<cd:artist>
<rdf:Bag>
<rdf:li>John</rdf:li>
<rdf:li>Paul</rdf:li>
<rdf:li>George</rdf:li>
<rdf:li>Ringo</rdf:li>
</rdf:Bag>
</cd:artist>
</rdf:Description>
</rdf:RDF>

rdf:Seq


<rdf:Description rdf:about=quot;http://www.recshop.fake/cd/Beatles_For_Salequot;>
<cd:artist>
<rdf:Seq>
<rdf:li>John</rdf:li>
<rdf:li>Paul</rdf:li>
<rdf:li>George</rdf:li>
<rdf:li>Ringo</rdf:li>
</rdf:Seq>
</cd:artist>
</rdf:Description>
</rdf:RDF>

40

rdf:Alt

<rdf:RDF
xmlns:rdf=quot;http://www.w3.org/1999/02/22-rdf-syntax-ns#quot;

<rdf:Description
rdf:about=quot;http://www.recshop.fake/cd/Beatles_For_Salequot;>
<cd:format>
<rdf:Alt>
<rdf:li>CD</rdf:li>
<rdf:li>Record</rdf:li>
<rdf:li>Tape</rdf:li>
</rdf:Alt>
</cd:format>
</rdf:Description>
</rdf:RDF>

41

RDF Container Semantics

Purely intuitive !

rdf:about vs. rdf:ID (1)
Two equivalent statements...

<?xml version=quot;1.0quot; encoding=quot;UTF-8quot;?>
<rdf:RDF
<rdf:Description
rdf:about=quot;http://starlab.vub.ac.be/staff/pdeleenheer#contactquot;>
<dc:title>Contact Information</dc:title>
</rdf:Description>
</rdf:RDF>

<rdf:RDF
xml:base=quot;http://starlab.vub.ac.be/staff/pdeleenheerquot; >
<rdf:Description rdf:ID=quot;contactquot;>
</rdf:Description>
</rdf:RDF>

rdf:about vs. rdf:ID (2)
Another pair of equivalent statements...

<?xml version=quot;1.0quot; encoding=quot;UTF-8quot;?>
<rdf:RDF
<rdf:Description
rdf:about=quot;http://starlab.vub.ac.be/staff/pdeleenheer#contactquot;>
</rdf:Description>
</rdf:RDF>

<rdf:RDF
xml:base=quot;http://starlab.vub.ac.be/quot; >
<rdf:Description rdf:ID=“staff/pdeleenheer#contactquot;>
</rdf:Description>
</rdf:RDF>

Reiﬁcation
• RDF triples are facts, statements
• It is true that ...
• The author of starlab.vub.ac.be is Peter Spyns
• what about statements about statements?
• I believe that ...
• I heard that ...
• RDF provides reification
• trust
• meta-data
• left as self-study

RDF Schema
• RDF describes resources with classes,
properties, and values
• RDFS is an extension to RDF
• RDFS provides a framework to describe
vocabulary, i.e. application-specific classes
and properties
• The term “schema” is similar to a DB
schema

RDFS Example

<rdf:RDF
xmlns:rdf= quot;http://www.w3.org/1999/02/22-rdf-syntax-ns#quot;
xmlns:rdfs=quot;http://www.w3.org/2000/01/rdf-schema#quot;
xml:base= quot;http://www.all-fruits-of-the-world.uto/exoticfruitquot;>

<rdf:Description rdf:ID=quot;exotic fruitquot;>
<rdf:type
rdf:resource=quot;http://www.w3.org/2000/01/rdf-schema#Classquot;/>
</rdf:Description>

<rdf:Description rdf:ID=quot;bananaquot;>
abbreviate?
<rdf:type
<rdfs:subClassOf rdf:resource=quot;#exotic fruitquot;/>
</rdf:Description>

<rdf:Description rdf:ID=quot;sapodillaquot;>
<rdf:type
</rdf:Description>

</rdf:RDF>

RDFS example abbr.

<rdf:RDF
xmlns:rdf= quot;http://www.w3.org/1999/02/22-rdf-syntax-ns#quot;
xmlns:rdfs=quot;http://www.w3.org/2000/01/rdf-schema#quot;
xml:base= quot;http://www.all-fruits-of-the-world.uto/exoticfruitquot;>

<rdfs:Class rdf:ID=quot;exotic fruitquot; />

<rdfs:Class rdf:ID=quot;bananaquot;>
Yes ! cfr. slide 26
</rdfs:Class>

<rdfs:Class rdf:ID=quot;sapodillaquot;>
</rdfs:Class>

</rdf:RDF>

RDF Classes
• rdfs:Resource – all resources within RDF are
implicitly member of this class
• rdfs:Class
• rdfs:Literal
• rdfs:XMLLiteral
• rdfs:Container
• rdfs:ContainerMembershipProperty
• rdfs:Datatype

RDF core properties
• rdfs:subClassOf • rdfs:subPropertyOf
• rdfs:isDefinedBy
• rdfs:seeAlso
• rdfs:comment
• rdfs:member
• rdf:type
• rdfs:label
• rdf:predicate
• rdf:subject
• rdf:first
• rdf:object
• rdfs:domain
• rdf:rest
• rdf:value
• rdfs:range

rdfs:Class
<rdf:RDF
xmlns:rdf=quot;http://www.w3.org/1999/02/22-rdf-syntax-ns#quot; xmlns:rdfs=quot;http://
Can be left implicit:
www.w3.org/2000/01/rdf-schema#quot;>
Resource=root
class
<rdfs:Class rdf:ID=quot;Personquot;>
<rdfs:comment>Person Class</rdfs:comment>
<rdfs:subClassOf rdf:resource=quot;http://www.w3.org/1999/02/22-
rdf- syntax-ns#Resourcequot;/>
</rdfs:Class>

<rdfs:Class rdf:ID=quot;Studentquot;>
<rdfs:comment>Student Class</rdfs:comment>
<rdfs:subClassOf rdf:resource=quot;#Personquot;/>
</rdfs:Class>

<rdfs:Class rdf:ID=quot;Teacherquot;>
<rdfs:comment>Teacher Class</rdfs:comment>
</rdfs:Class>

<rdfs:Class rdf:ID=quot;Coursequot;>
<rdfs:comment>Course Class</rdfs:comment>
<rdfs:subClassOf rdf:resource=quot;http://www.w3.org/1999/02/22-
rdf- syntax-ns#Resourcequot;/>
</rdfs:Class>

rdf:Property
<rdf:Property rdf:ID=“hasTeacherquot;>
<rdfs:comment>Teacher of a course</rdfs:comment>
<rdfs:domain rdf:resource=quot;#Coursequot;/>
<rdfs:range rdf:resource=quot;#Teacherquot;/>
</rdf:Property>

<rdf:Property rdf:ID=“hasEnrolledStudentsquot;>
<rdfs:comment>List of Students of a course in alphabetical
order</rdfs:comment>
<rdfs:range rdf:resource=quot;http://www.w3.org/1999/02/22-rdf-
syntax- ns#Seqquot;/>
</rdf:Property>

<rdf:Property rdf:ID=“hasNamequot;>
<rdfs:comment>Name of a Person or Course</rdfs:comment>
<rdfs:domain rdf:resource=quot;#Personquot;/>
<rdfs:range rdf:resource=quot;http://www.w3.org/1999/02/22-rdf-
syntax- ns#Literalquot;/>
</rdf:Property>

</rdf:RDF>

RDF Goodies
• No distinction between classes and instances
(individuals)
<Species,type,Class>
<Lion,type,Species>
<Leo,type,Lion>

• Properties can themselves have properties
<hasDaughter,subPropertyOf,hasChild>
<hasDaughter,type,familyProperty>

• No distinction between language constructors and
ontology vocabulary, so constructors can be applied to
themselves/each other
<type,range,Class>
<Property,type,Class>
<type,subPropertyOf,subClassOf>

RDF triple versus lexon

Lexons are : RDF triples are:
• valid in a certain
• valid in a certain
namespace
context
• binary relationships
• binary relationships
between resources
between concepts
• read in one direction
• read in two directions
• URIs
• natural language
terms

Lexon to RDFS

<drives rdf:resource=quot;#Carquot;/>
</rdfs:Class>

<rdfs:Class rdf:ID=“Carquot;>
<driven_by rdf:resource=quot;#Personquot;/>
</rdfs:Class>

<rdf:Property rdf:ID=“drivesquot;>
<rdfs:range rdf:resource=quot;http://www.w3.org/2000/01/rdf-schema#Classquot;/>
<rdfs:domain rdf:resource=quot;http://www.w3.org/2000/01/rdf-schema#Classquot;/>
</rdf:Property>

<rdf:Property rdf:ID=“driven_byquot;>
</rdf:Property>

RDFS to Lexon
<drives rdf:resource=quot;#Carquot;/>
<fancies rdf:resource=quot;#Carquot;/>
</rdfs:Class>

<rdfs:Class rdf:ID=“Carquot;>
</rdfs:Class>

<rdf:Property rdf:ID=“drivesquot;>
</rdf:Property>

<rdf:Property rdf:ID=“driven_byquot;>
</rdf:Property>

<rdf:Property rdf:ID=“fanciesquot;>
</rdf:Property>

<rdf:Property rdf:ID=“fancied_byquot;>
</rdf:Property>

RDFS to Lexon

Lexons  RDF  Lexons results in
loss of information

RDFS to Lexons
• From RDF triples
<s:WebPage about=quot;http://starlab.vub.ac.be/staff/pdeleenheerquot;>
</s:WebPage>

• From RDFS class and property definitions
<rdf:Property rdf:ID=“hasTeacherquot;>
<rdfs:comment>Teacher of a course</rdfs:comment>
<rdfs:range rdf:resource=quot;#Teacherquot;/>
</rdf:Property>

• From subclass definitions
<rdfs:Class rdf:ID=quot;Studentquot;>
<rdfs:comment>Student Class</rdfs:comment>
</rdfs:Class>

SOAP
• SOAP stands for Simple Object Access Protocol
• SOAP is a communication protocol
• SOAP is for communication between applications
• SOAP is a format for sending messages
• SOAP is designed to communicate via Internet
• SOAP is platform independent
• SOAP is language independent
• SOAP is based on XML
• SOAP is simple and extensible
• SOAP allows you to get around firewalls
• SOAP will be developed as a W3C standard

SOAP Message Format
<soap:Envelope xmlns:soap=quot;http://www.w3.org/2001/12/soap-
envelopequot; soap:encodingStyle=quot;http://www.w3.org/2001/12/
soap-encodingquot;>
<soap:Header>
...
...
</soap:Header>
<soap:Body>
...
...
<soap:Fault>
...
...
</soap:Fault>
</soap:Body>
</soap:Envelope>

SOAP Message Format
soap-encodingquot;>
<soap:Header>
...
...
</soap:Header>
<soap:Body> The xmlns:soap namespace should always
... have the value of http://www.w3.org/
2001/12/soap-envelope
...
and it defines the Envelope as a SOAP
<soap:Fault>
Envelope
...
...
</soap:Fault>
</soap:Body>
</soap:Envelope>

SOAP Message Format
soap-encodingquot;>
<soap:Header>
...
...
</soap:Header>
<soap:Body>
A SOAP Envelope has no default encoding
...
style. It is a client-server agreement.
...
<soap:Fault>
...
...
</soap:Fault>
</soap:Body>
</soap:Envelope>

SOAP Message Format
soap-encodingquot;>
<soap:Header>
...
...
</soap:Header>
<soap:Body> The optional Header contains application
... specific information (like authentication,
payment, etc) about the SOAP message.
...
<soap:Fault>
The attributes defined in the SOAP Header
...
defines how a recipient should process the
...
SOAP message.
</soap:Fault>
</soap:Body>
</soap:Envelope>

SOAP Message Format
soap-encodingquot;>
<soap:Header>
...
The required SOAP Body element contains
...
the actual SOAP message intended for the
</soap:Header>
ultimate endpoint of the message.
<soap:Body>
Immediate child elements of the SOAP Body
...
element may be namespace-qualified.
...
SOAP defines one element inside the Body
<soap:Fault>
element in the default namespace (quot;http://
... www.w3.org/2001/12/soap-envelopequot;). This
... is the SOAP Fault element, which is used to
</soap:Fault> indicate error messages.
</soap:Body>
</soap:Envelope>

SOAP Example
<SOAP-ENV:Envelope
xmlns:SOAP-ENV=“
http://schemas.xmlsoap.org/soap/envelope/quot;
xmlns:xsi=quot;
http://www.w3.org/1999/XMLSchema-instancequot;
xmlns:xsd=quot;http://www.w3.org/1999/XMLSchemaquot;>
<SOAP-ENV:Header>
</SOAP-ENV:Header>
<SOAP-ENV:Body>
<ns1:sayHelloTo xmlns:ns1=quot;Hello”
SOAP-ENV:encodingStyle=quot;
http://schemas.xmlsoap.org/soap/encoding/quot;>
<name xsi:type=quot;xsd:stringquot;>John</name>
</ns1:sayHelloTo
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

SOAP Example
<SOAP-ENV:Envelope
xmlns:SOAP-ENV=“http://schemas.xmlsoap.org/soap/envelope/quot;
xmlns:xsi=quot;http://www.w3.org/1999/XMLSchema-instancequot;
xmlns:xsd=quot;http://www.w3.org/1999/XMLSchemaquot;>
<SOAP-ENV:Body>
<ns1:sayHelloToResponse
xmlns:ns1=quot;Hello“
SOAP-ENV:encodingStyle=“
http://schemas.xmlsoap.org/soap/encoding/quot;>
<return xsi:type=quot;xsd:stringquot;>Hello John, How are you
doing?
</return>
</ns1:sayHelloToResponse>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Online Public Services
• Validation http://www.w3.org/RDF/Validator
• Meta-data generators
• Reggie
(http://metadata.net/dstc/)
• UKOLN Dublin Core dot (http://www.ukoln.ac.uk/metadata/
dcdot/)
• Reusable vocabularies
• Dublin Core (xmlns:dc=“http://purl.org/dc/elements/1.1/”)
• vCard
• and many more

Publicly Available Tools
• Editors
• IsaViz http://www.w3.org/2001/11/IsaViz/
• RDFeditor http://sourceforge.net/projects/rdfeditor/
• Browsers
• BrownSauce http://brownsauce.sourceforge.net/
• Stand-alone Parsers
• ARP2 http://hpl.hp.com/semweb/arp.htm (also in
Jena)
• ICS-FORTH http://athena.ics.forth.gr:9090/RDF/
(also in RDF Suite)

RDFS Shortcomings
• RDFS too weak to describe resources in sufficient detail
– No localised range and domain constraints
• Impossible to say that the range of hasChild is person when applied
to persons and elephant when applied to elephants
– No existence/cardinality constraints
• Impossible to say that all instances of person have a mother that is
also a person, or that persons have exactly 2 parents
– No transitive, inverse or symmetrical properties
• Impossible to say that isPartOf is a transitive property, that hasPart
is the inverse of isPartOf or that touches is symmetrical
– etc.
• Difficult to provide reasoning support
– No “native” reasoners for non-standard semantics
– May be possible to reason via first-order axiomatisation

Web Ontology Language
Desirable features identified for Web Ontology Language:

• Extends existing Web standards
– Such as XML, RDF, RDFS
• Easy to understand and use
– Should be based on familiar KR idioms
• Formally specified
• Of “adequate” expressive power
• Possible to provide automated reasoning support

RDF to OWL
• Two languages developed to satisfy above requirements
– OIL: developed by group of (largely) European researchers (several
from EU OntoKnowledge project)
– DAML-ONT: developed by group of (largely) US researchers (in DARPA
DAML programme)
• Efforts merged to produce DAML+OIL
– Development was carried out by “Joint EU/US Committee on Agent
Markup Languages”
– Extends (“DL subset” of) RDF
• DAML+OIL submitted to W3C as basis for standardisation
– Web-Ontology (WebOnt) Working Group formed
– WebOnt group developed OWL language based on DAML+OIL
– OWL language now a W3C Candidate Recommendation

OWL Specs
• Three species of OWL
– OWL full is union of OWL syntax and RDF
– OWL DL restricted to FOL fragment (¼ DAML+OIL)
– OWL Lite is “easier to implement” subset of OWL DL
• OWL DL based on SHIQ Description Logic
– In fact it is equivalent to SHOIN(Dn) DL
• OWL DL Benefits from many years of DL
research
– Well defined semantics
– Formal properties well understood (complexity,
decidability)
– Known reasoning algorithms
– Implemented systems (highly optimised)

OWL Constructors

• XMLS datatypes as well as classes in
– E.g.,
• Arbitrarily complex nesting of constructors
– E.g.,

RDF Syntax for OWL
E.g.,
<owl:Class>
<owl:intersectionOf rdf:parseType=quot; collectionquot;>
<owl:Class rdf:about=quot;#Personquot;/>
<owl:Restriction>
<owl:onProperty rdf:resource=quot;#hasChildquot;/>
<owl:toClass>
<owl:unionOf rdf:parseType=quot; collectionquot;>
<owl:Class rdf:about=quot;#Doctorquot;/>
<owl:Restriction>
<owl:onProperty rdf:resource=quot;#hasChildquot;/>
<owl:hasClass rdf:resource=quot;#Doctorquot;/>
</owl:Restriction>
</owl:unionOf>
</owl:toClass>
</owl:Restriction>
</owl:intersectionOf>
</owl:Class>

References
1. Heflin, J. and Allamang. (2008) Semantic Web for the Working
Ontologist
2. Hjelm, J. (2001) Creating the Semantic Web with RDF, Wiley.
3. Powers, S. (2003) Practical RDF, O’Reilly.
4. Baader, F. and Nutt, W. (2002) Basic Description Logics. In the
Description Logic Handbook, Cambridge University Press, pp.
47-100.
5. http://www.w3.org/TR/owl-guide/
6. http://www.javaworld.com/javaworld/jw-03-2001/jw-0330-
soap.html
7. http://www.w3schools.com

Open Standards Guide to Semantic Web Languages

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