DataMining versus SemanticWeb

1
DataMining versus SemanticWeb

• Veljko Milutinovic, vm_at_etf.bg.ac.yu
• http//galeb.etf.bg.ac.yu/vm

2
DataMining versus SemanticWeb

• Two different avenues leading to the same goal!
• The goal Efficient retrieval of knowledge,from
  large compact or distributed databases, or the
  Internet
• What is the knowledge Synergistic interaction
  of information (data)and their relationships
  (correlations).
• The major difference Placement of complexity

3
Essence of DataMining

• Data and knowledge representedwith simple
  mechanisms (typically, HTML)and without metadata
  (data about data).
• Consequently, relatively complex algorithms have
  to be used (complexity migratedinto the
  retrieval request time).
• In return,low complexity at system design time!

4
Essence of SemanticWeb

• Data and knowledge representedwith complex
  mechanisms (typically XML)and with plenty of
  metadata (a byte of data may be accompanied
  with a megabyte of metadata).
• Consequently, relatively simple algorithms can
  be used (low complexity at the retrieval request
  time).
• However, large metadata designand maintenance
  complexityat system design time.

5
Major Knowledge Retrieval Algorithms (for
DataMining)

• Neural Networks
• Decision Trees
• Rule Induction
• Memory Based Reasoning,
• etc
• Consequently, the stress is on algorithms!

6
Major Metadata Handling Tools (SemanticWeb)

• XML
• RDF
• Ontology Languages
• Verification (Logic Trust) Efforts in Progress
• Consequently, the stress is on tools!

7
Semantic Web Tutorial Structure (Overview)

• Introduction to the Semantic Web
• XML Technologies for the Semantic Web
• Defining vocabularies with RDF
• Ontologies and ontology languages
• Challenges for the Semantic Web
• References

8
World Wide Web - Today
Information consumer
preferences
preferences
Information request
Search Engines (eg. Google), Information Portals
Indexing, refences, collections
Information and Service Providers
9
Semantic Web - Vision
User
Preferences

Calendar

Calendar
Preferences
Information and Service Provider
10
A Definition of the Semantic Web

• Semantic Web is an extension of the current
  web in which
  information is given well-defined meaning, better
  enabling computers and people to work in
  cooperation
• Tim Berners-Lee, James Hendler, Ora Lassila,
  The Semantic Web, Scientific American, May 2001

11
Why?

• To use the large amount of information on the Web
  more effectively
• To enable more advanced automated processing on
  the Web - machines can understand the content
• Intelligent browsers
  to help you
  find what you are looking for
• To derive new information from existing
  information (reasoning) - Virtual global database
• Advanced applications and services become
  possible, e.g. in
• - e-business
• - e-government
• - e-learning

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Examples

• Context-awareness -- linking based on the meaning
  of the information elements
• Filtering -- you could rate the pages you visit,
  and this is later used for automatic general
  recommendations
• Annotations -- you could add comments to the
  information on the Web, and these comments can
  be shown to other visitors
  
• Privatization -- you can create your own database
  of information from the Web

13
How? - Semantic Web layer model
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Trusted Web Resources
DAMLOIL
Shared Terminology
machine ??machine 2010
OWL
XML
Self Describing
Documents 2000
RDF
HTTP
Foundation of Web today 1990
Human ??Machine
HTML
SGML
Document Exchange Format 1985
Hy Time
15
Building Blocks
Semantic Web
Metadata
URI
Data about data labeling and
structuring information in a document
Universal Resource Identifier an
universal and unique name for any resource
http//www.something.com/one
16
Minimalist Design

• Making it as simple as possible
• Simplicity helps future evolution of Semantic Web

17
Inference

• Deriving new data from the existing ones
• Merging data repositories gives new information
• Allows the creation of more powerful applications
  (intelligent agents)
• Unfortunately, inference can be achieved
  completely only when the semantics is defined
  formally in a language(e.g. "First Order
  Predicate Logic languages)

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Tutorial Structure

• Introduction to the Semantic Web
• XML Technologies for the Semantic Web
• Defining vocabularies with RDF
• Ontologies and ontology languages
• Challenges for the Semantic Web
• References

19
XML Technologies for the Semantic Web

• Overview
• XML Instances
• XML Document Type Definition
• XML Linking
• XML Schema
• XML Query Language

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What is an XML-Document ?
lt?xml version"1.0"?gt ltagt ltb id"x1"gt
ltcgtDavidlt/cgt ltcgtMarielt/cgt lt/bgt
ltd/gt ltb id"x2"gt ltcgtJohnlt/cgt
lt/bgt lt/agt
a
a
idx1
idx2

b
d
b
b
d
id
c
c
c

c
David
Marie
John
Schema (Document Type Definition, DTD)
File Format (Instance)
Tree Structure Instance
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The XML Stack
Specific Applications
Standardized Applications XHTML, SVG, SMIL, P3P,
MathML
Metadata - RDF, RDFS
Hyperlinks - XLink - XPointer
Layout - XSL - CSS
Schemas - XSD - Namespaces
API - DOM - SAX
Queries - XPath - XQuery
XML 1.0
Unicode
Locators (URI)
DTDs
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Example of songs.xml

• Example of describing a song in songs.xml using
  music.dtd
• ltsonggt
  lttitlegtGipsy songlt/titlegt
  ltartistgtVlatko Stefanovskilt/artistgt
  lttype classETHNO /gtltdownload
  classYES/gtltcomments/gtlt/songgt

parent element
defined in music.dtd
child elements
defined in music.dtd
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Music.dtd
Parent element

• lt!ELEMENT song (title, artist, album?, type,
  format?, download, comments?)gt
• lt!ELEMENT title (PCDATA)gt
• lt!ELEMENT artist (PCDATA)gt
• lt!ELEMENT type EMPTYgt
• lt!ATTLIST type
• class (CLASSICAL ROCK POP RAP
• JAZZ TECHNO ETHNO) REQUIREDgt
• lt!ELEMENT download EMPTYgt
• lt!ATTLIST download
• class (YES NO) "YES"
• gt
• lt!ELEMENT comments (PCDATA)gt

Child elements
Attributes describe content
List of values for download
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XML Linking
Simple Link
Extended Link
XPointer
Link Group
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XPath

• A language that enables us to address parts of an
  XML document (elements, attributes, )
• Select the title elements of the song elements
  of the catalog element and all the artist
  elements in the document
• /catalog/song/title //artist
  
• Selects all the song elements of the catalog
  element that have a download element with a value
  of yes
• /catalog/songdownloadyes/title

selects any element in the document
selects the child element
selects several paths
26
Also

• Use to select unknown XML elements
• /catalog//artist
• Use _at_attribute_name to specify an attribute
• //song_at_typeclassical'
• XPath expressions logical, arithmetical
• /catalog/songdurationlt5
• XPath functions - count(), id(), last(), name(),
  concat(), string(), trenslate(), sum(), round(),
  false(), not(),
• /catalog/songlast()
• To select nodes from the XML document (IE)
• xmlDoc.selectNodes("/catalog/song/title/text()")

the path
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XPointer

• Locates portions of other XML documents
  (elements, attributes), without the need to
  place anchors inside those documents (as in
  HTML)
• More robust to the changes in the target document
• URL XPath
• http//www.music.org/first.xml/xpointer(//song/ti
  tle1)

XPointer expression (XPath language)
URL of the document we point into
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XML Schema

• XML Schema defines a class of XML documents
• Defines (explains) the datatypes, elements, and
  attributes
• Defines and catalogues vocabularies
  for classes of XML documents
• The document described by an XML schema
  can be called an instance (parallel to
  OOP)
• The schema language, considerably extends the
  capabilities of XML 1.0 document type definitions
  (DTDs), most importantly with datatypes

29
Limitations of DTDs
Practically no reuseof contentmodels
Syntax Not XML

• lt!ELEMENT song (title, artist, album?, type,
  format?, download, comments?)gt
• lt!ELEMENT title (PCDATA)gt
• lt!ELEMENT artist (PCDATA)gt
• lt!ELEMENT type EMPTYgt
• lt!ATTLIST type
• class (CLASSICAL ROCK POP RAP
  JAZZ TECHNO ETHNO) REQUIREDgt
• lt!ELEMENT download EMPTYgt
• lt!ATTLIST download
• class (YES NO) "YES"gt
• lt!ELEMENT comments (PCDATA)gt

Constructors Elementset withContent Model
Datentypes Essentially only "String"
30
XML Schema Components

• An XML Schema is comprised of a set of schema
  components
• There are three groups of components
• Primary components - Simple type definitions,
  Complex type definitions, Attribute declarations,
  Element declarations
• Secondary components - Attribute group
  definitions, Identity-constraint definitions,
  Model group
  definitions, Notation declarations
• Helper components Annotations, Model groups,
  Particles, Wildcards, Attribute Uses

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Example song
Type definition

• ltxsdcomplexType namesong" gt
  ltxsdsequencegt
  ltxsdelement nametitle"
  type"xsdstring"/gt ltxsdelement nameartist"
  type"xsdstring"/gt lt/xsdsequencegt
• ltxsdattribute namelength" type"xsdduration"/gt
  lt/xsdcomplexTypegt
• xsd used to denote XML Schema namespace

Complex type
ltxsdchoicegt
Simple type
Type declarations
lt/xsdchoicegt
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Reusability of schemas

• xsinclude to include a schema from another
  document (copy-paste)
• ltxsinclude schemaLocationcollection.xsd"/gt
• xsredefine same, plus it lets you redefine
  schema
• xsimport - reusing definitions from other
  namespaces (a system of libraries)
• ltxsimport namespace"http//www.w3.org/XML/1998/
  namespace" schemaLocation"myxml.xsd"/gt
• Now we can reference an external element from
  the imported namespace in our schema

33
Tutorial Structure

• Introduction to the Semantic Web
• XML Technologies for the Semantic Web
• Defining vocabularies with RDF
• Ontologies and ontology languages
• Challenges for the Semantic Web
• References

34
Defining vocabularies with RDF

• Motivation for RDF
• RDF Instances
• Basic concepts and building blocks
• Syntax options
• Reification
• Collections
• RDF Schema Defining your own Vocabularies
• Supporting Interoperability with RDF

35
What do we NOT get from XML?

• Superimposing (meta) information
• XML combines metainformation and content
• Datatypes that we can reason about
• ExampleCLASSICAL ROCK POP RAP JAZZ
  TECHNO ETHNOis just a choice of allowed
  strings. We cannot represent that DIXIE is a
  subclass of JAZZ, BLUES overlaps with ROCK,
  ETHNO
• Bottom up reuse of vocabularies
• Independently evolved XML Schemas for one and
  the same thing
• How do you model an address?

36
RDF Defining Semantics on the Web

• There is a need to describe resources on the Web
  in a form that can be interpreted by machines
  across the Web
• Interpretation depends on the context of a
  resource eg. Jaguar (car vs. beast)
• Using their experience and cognitive abilities
  humans may infer the context of a resource in
  many ways, even if it is not made explicit
• Software can interpret context only if it is
  described explicitly and formally
• RDF and the ontology languages building upon RDF
  provide means to explicate (part of) this context

37
RDF-Resource Description Framework

• Defines a framework for structuring and
  describing resources like documents in the
  Semantic Web
• Enables the definition of vocabularies for the
  description of resources in an application
  domain
• Goals
• Extensibility, interoperability, and reuse of
  vocabularies
• Improved support for interpretation of data by
  machines

38
The RDF Data Model

• Simple but powerful datamodel for the description
  of resources and the creation of metadata
• Consists of three core concepts
• Resource
• Property
• Statement
• Class (in RDF Schema)
• Similar to other modeling approaches (e.g.
  object-oriented modeling), but property-centric,
  not class-centric

39
RDF Statement and Graph

• Each triple (S, P, O) node - arc - node
  represents an RDF statement
• Gipsy song is performed by Vlatko Stefanovski.

subject (resource)
object (resource or literal)
predicate (property)
http//www.music.org/songs/g/gipsySong
http//www.artist.org/stefanovski
Performed by
Artist represented by his homepage
Song represented by entry in a (fictive) song
directory
40
Arcs in the RDF Graph

• An Arc
• represents the predicate of an RDF statement
• is labeled with a URI referring to an RDF
  property
• is directed pointing from the subject of a
  statement to the object of a statement

object
subject
predicate
http//www.artist.org/stefanovski
http//www.music.org/songs/g/gipsySong
musicperformed by
41
RDF Resource

• The Resource forms the central concept in RDF
• Anything that can be described can act as a
  resource
• Web page, part of web page, web site, book,
  photograph, persons,
• Resources are identified by a
  resource identifier - URI (plus
  optional anchor IDs)
• Compare for an entity
  (in the Entity Relationship
  model) or an
  object (in an object-oriented model)

42
RDF Property

• An RDF Property is used to express
• A characteristic of an resource or
• A binary relation between resources
• A predicate in a statement
• A property can be compared to a (binary)
  relationship among entities (in the Entity
  Relationship model)

43
Example

• The individual whose name is Vlatko Stefanovski
  and whose email is V.Stefanovski_at_artists.org, is
  the artist of http//www.music.org/songs/g/gipsySo
  ng

URI reference
http//www.music.org/songs/g/gipsySong
blank node
musicartist
node
personname
personhomepage
Vlatko Stefanovski
http//www.artists.org/stefanovski
literal
44
XML Serialization

• How to translate the RDF graph structure into
  XMLs tree-oriented notation
• ltrdfDescription rdfabout http//www.music.or
  g/songs/g/gipsySonggt
• ltmusicperformedbygt
  
  
• ltrdfDescriptiongt
• ltpersonnamegt Vlatko Stefanovskilt/personn
  amegt
• ltpersonhomepagegt
• ltrdfDescription
• about http//www.artists.org
  /stefanovskigt
• lt/rdfDescriptiongt
• lt/personhomepagegt
• lt/rdfDescriptiongt
• lt/musicperformadbygt
  
• lt/rdfDescriptiongt

http//www.music.org/songs/g/gipsySong
musicperformedby
personname
personhomepage
http//www.artists.org/stefanovski
Vlatko Stefanovski
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Reification

• Latin Res ... Thing -gt Reification ... Thing
  Making
• Statements themselves can be considered as
  resources (things) in RDF. Thus, it is possible
  to make statements about statements
  (Reification).
• Possible applications
• Definition of a context for a statement with
  respect to time, place, validity, .
• Embed a statements into a discourse (claims,
  doubts, proofs of statements)
• Example
• Statement A ltsonata XYgt ltcomposergt ltMozartgt
• Statement B ltmusic expert Agt ltclaimsgt ltstatement
  Agt
• ltmusic expert Cgt ltdoubtsgt ltstatement Agt

46
Reification Syntax

• The statement to be reified has to be modeled as
  an RDF resource
• The RDF vocabulary provides special constructs
  for this purpose
• The class rdfStatements which is the type of
  all RDF statements.
• The property rdftype which is used to associate
  an RDF resource with a class.
• The property rdfsubject refers to the subject
  of the modeled statement (i.e. to the described
  resource)
• The property rdfpredicate refers to the property
  used as a predicate in the modeled statement
• The property rdfobject refers to the object of
  the modeled statement (i.e. the property value)

47
How to create a reified statement?

• Associate the subject, predicate and object of
  the statement with the resource rdf Statement
  This is done by using the rdfsubject,
  rdfpredicate and rdfobject properties

rdfStatement
rdftype
rdfsubject
rdfpredicate
rdfobject
musiccomposer
www.operas.org/Zauberflöte
www.operas.org/Zauberflöte
www.artists.org/Mozart
www.artists.org/Mozart
musiccomposer
48
How to create a reified statement?

• Now the created node which represents the
  statements can be used as an object or subject
  of another RDF statement

Statement becomes a resource
www.musicExperts.org/ExpertA
rdfStatement
rdftype
musicclaimedBy
rdfsubject
rdfpredicate
rdfobject
musiccomposer
www.operas.org/SonataXY
www.artists.org/Mozart
49
XML Syntax for Reification

• ltrdfRDF xmlnsrdf "http//w3.org/1999/02/22-rdf
  -syntax-ns" xmlnsmusic"http//ipsi
  .fhg.de/music-schema"gt
• ltrdfDescriptiongt
• ltrdftype resource" http//w3.org/1999/02/22-rd
  f-syntax-nsStatement gt
  
• ltrdfsubject resource"http//www.operas.org/Son
  ataXY " /gt
• ltrdfpredicate resource"http//ipsi.fhg.de/musi
  c-schemaComposer" /gt
• ltrdfobject resource http//www.artists.org/M
  ozart /gt
• ltmusicclaimedBy resource
  http//www.musicExperts.org/ExpertA /gt
  
  
  
• lt/rdfDescriptiongt
  
• lt/rdfRDFgt

Property of the statement
50
RDF Collections

• An RDF Container models a collection of
  resources.
• The RDF model supports three types of 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 (single)
  value of a property.
• Bag and Sequence can be used for multivalued
  properties

51
Container - RDF Graph Syntax

• Example Collection of Arias

rdfSequence
rdftype
/Aria1
rdf_1
http//www.opera.org/Zauberflöte
/Aria2
rdf_2
musicarias
rdf_3
/Aria3
rdf_4
/Aria4
52
Container - XML Syntax

• ltrdfRDFgt
  ltrdfDescription
  about"http//www.operas.org/Zauberflöte"gt ltmusic
  ariasgt ltrdfSequencegt ltrdfli
  resource/Aria1gt
• ltrdfli resource/Aria2"/gt
• ltrdfli resource/Aria3"/gt
• ltrdfli resource/Aria4"/gt
• lt/rdfSequencegt
  
• lt/musicariasgt
  
• lt/rdfDescriptiongt
  
• lt/rdfRDFgt

53
Statements about a Container and its members

• rdfabout is used to make a statement on the
  comtainer as a whole
• rdfaboutEach is used to make a statement about
  each of the members of the container
• rdfaboutEachPrefix makes a statement about each
  member resource of a Bag that is only implicitly
  defined. This Bag contains all the resources
  whose fully resolved resource identifiers begin
  with the character string given as the value of
  the attribute

54
RDF Schema

• The RDF vocabulary description language - RDF
  Schema stresses
• Reuse and extension of existing schemata
• Semantic enrichment by concept hierarchies
• Enables statements on the schema level to
• define classes of resources
• define relationships between these classes
• define the kinds of properties that instances of
  that classes have
• define relationships between properties
• to restrict possible combinations of classes and
  relationships/properties
• Allows mixing of schemata

55
Defining an RDF Class (Example)

• Class
• ltrdfsClass rdfabout http//www.ipsi.fhg.de/mu
  sic-schemaMusicCompositiongt
• ltrdfssubClassOf rdfresource http//www.w3.org
  /2000/rdf-schemaResourcegt
• ltrdfslabelgtMusicCompositionlt/rdfslabelgt
• lt/rdfsClassgt
• Instance
• ltrdfDescription about http//www.operas.org/Za
  uberflötegt
• ltrdftype
• rdfresource http//www.ipsi.fhg.de/music-sche
  maMusicComposotion gt
• lt/rdftypegt
• lt/rdfDescriptiongt

rdfsResource
rdfssubClassOf
musicMusicComposition
rdftype
www.operas.org/Zauberflöte
56
Class-centric vs. Property-centric

• Class-centric
• Attributes as part of the class definition
• Stresses common structure

• Property-centric
• Property as first-class object
• Stresses extensibility and flexibility with
  respect to properties

musiccomposer
rdfsrange
rdfsdomain
musicMusicTitle
personPerson
rdfsLiteral
rdfsrange
rdfsdomain
rdflabel
57
Defining Concept Hierarchies

• rdfssubClassOf represents a specialization
  relationship between RDF classes (transitive).

musicGenre
rdfssubClassOf
rdfssubClassOf
musicModern
musicClassic
rdfssubClassOf
rdfssubClassOf
rdfssubClassOf
musicSonata
musicRock
musicOpera
rdfssubClassOf
rdftype
rdfssubClassOf
musicRockOpera
http//www.operas.org/Zauberflöte
rdftype
musicMusicTitle
58
RDF Property Hierarchies

• rdfssubPropertyOf
• Is used to specify that one property is a
  specialization of another property
• If a resource r has value v for property p1 and
  property p1 is subproperty of p2 than r also has
  value v for property p2.

SomeSong is also a value of performs
performs
SomeSong
rdfssubPropertyOf
SomeSong is a value for sings
sings
performs
sings
Cher
59
Tutorial Structure

• Introduction to the Semantic Web
• XML Technologies for the Semantic Web
• Defining vocabularies with RDF
• Ontologies and ontology languages
• Challenges for the Semantic Web
• References

60
Ontologies and Ontology Languages

• What is an Ontology?
• The Ontology Language OWL
• Taxonomies
• Property Restrictions

61
Ontology

• An ontology is a specification of a
  conceptualization.
• A conceptualization is an abstract, simplified
  view of the world that we wish to represent for
  some purpose.
• T. R. Gruber. A translation approach to portable
  ontologies. Knowledge Acquisition, 5(2)199-220,
  1993

62
Ontology Languages

• Ontology languages are semantic markup languages
  for defining ontologies
• DAMLOIL is a combination of the two predecessor
  ontology languages
• DAML DARPA Agent Markup Language
• OIL - Ontology Inference Layer
• OWL (Web Ontology Language) is the successor DAML
  OIL currently developed by the W3C Web Ontology
  Group (Status Working Draft)
• Building on RDF ideas
• OWL Lite is a subset of OWL

63
OWL Characteristics

• OWL enables the definition of
• various types of relationships between classes
  (in addition to subclass hierarchies)
• additional restrictions for property values
• additional types of relationships between
  properties
• different kinds of properties
• OWL distinguishes between classes and instances
  (objects) on the one side, and data types and
  value on the other side (XML Schema datatypes)

64
Ontology Definition

• The body of the ontology consists of
• classes
• properties
• instances (for use in class definitions)
• The main component of an ontology is a taxonomy
  i.e. a class hierarchy

65
Further Class Relationships

• A class definition may also contain other class
  relationships
• owldisjointWith this property is used to
  express that a class is disjoint with another
  class (no instances in common)
• owlsameClassAs - this property is used to
  express that a class is equivalent to another
  class (same instances)
• The values of these properties are defined by a
  class expressions, which in the simplest case is
  the name (URI) of a class

66
Properties in OWL

• OWL properties are deferred from RDF properties
• It is possible to define
• different types of properties,where several
  property types can be combined with each other
• relationships between properties

67
Tutorial Structure

• Introduction to the Semantic Web
• XML Technologies for the Semantic Web
• Defining vocabularies with RDF
• Ontologies and ontology languages
• Challenges for the Semantic Web
• References

68
Logic and Proof

• Deduction checking a document against a set of
  rules
• Add predicate logic and quantifiers
• Logic Digital Signature ? Proof

Oh yeah! Prove it.
You owe me 30.
The check is in the email!
Purchased(user1.book1.AOL)www.confirm.comt12211
22 Priceof(book1, 30)AOL-historyDBt29293910
Purchase(a,b,c)
Priceof(b,d)?Owes(a,c,d)www.ont.com/prodont
69
Instead of a Conclusion IPSI Projects

• Scalable Technology and Applicationsfor
  theSemantic Web

70
Individualized Electronic Newspaper
71
Dictionary of Art
72
XML Broker Integrating Web Resources via XML
ltgolfdemo ltgolfplatzgt ltadressegt ...
lt/adressegt ltgreenfeegt ... lt/greenfeegt
... lt/golfplatzgt ltwettergt ...
lt/wettergt ltroutegt ... lt/routegt lt/golfdemogt
XSL
XML Broker
Query
73
Virtual Gallery