semantic search with semantic web

Download Semantic Search with Semantic Web

Post on 22-Jan-2017

277 views

Category:

Internet

3 download

Embed Size (px)

TRANSCRIPT

  • Semantic Search with

    Semantic Web

    Presented by:

    Zahra Sadeghi

    1

  • keyword-based search engines

    the quality of the search results:

    It often happens that relevant pages are not indexed by a traditional search engine

    very time-consuming task for the users who have to perform it manually.

    the result of a search engine is a single web page, and to retrieve information it is necessary to perform several queries.

    semantically similar queries can return different results

    very closely related to the spelling of the word and not to its meaning

    important information can be reached only if its specific internet address is known.

    2

  • The Original Web 1989: Web was invented by Tim Berners-Lee

    3

    Web of relationships amongst named objects

    http://www.w3.org/People/Berners-Lee/

  • Where we are Today

    4

  • What is the Problem?

    Consider a typical web page:

    The current Web represents information using: - natural language ( English,) -graphics, multimedia Humans can process this easily can deduce facts from partial information

    5

    Semantic content is accessible to

    humans but not (easily) to

    computers

  • What information can we see WWW2002

    The eleventh international world wide web conference

    Sheraton waikiki hotel

    Honolulu, hawaii, USA

    7-11 may 2002

    1 location 5 days learn interact

    Registered participants coming from

    australia, canada, chile denmark, france, germany, ghana, hong kong, india, ireland, italy, japan, malta, new zealand, the netherlands, norway, singapore, switzerland, the united kingdom, the united states, vietnam, zaire

    Register now

    On the 7th May Honolulu will provide the backdrop of the eleventh international world wide web conference. This prestigious event

    Speakers confirmed

    Tim berners-lee

    Tim is the well known inventor of the Web,

    Ian Foster

    Ian is the pioneer of the Grid, the next generation internet

    6

  • What information can a machine

    see WWW2002

    The eleventh inteqnational woqld wide web

    confeqence

    Sheqaton waikiki hotel

    Honolulu, hawaii, USA

    7-11 may 2002

    1 location 5 days leaqn inteqact

    Registeqed paqticipants coming fqom

    austqalia, canada, chile denmaqk, fqance,

    geqmany, ghana, hong kong, india,

    iqeland, italy, japan, malta, new zealand,

    the netheqlands, noqway, singapoqe,

    switzeqland, the united kingdom, the united

    states, vietnam, zaiqe

    Registeq now

    On the 7th May Honolulu will pqovide the

    backdqop of the eleventh inteqnational woqld

    wide web confeqence. This pqestigious event

    Speakeqs confiqmed

    Tim beqneqs-lee

    Tim is the well known inventoq of the Web,

    Ian Fosteq

    Ian is the pioneeq of the Gqid, the next

    geneqation inteqnet

    7

  • The current Web =

    the second Web generation

    The first generation Web started with handwritten HTML pages; The second generation made the step to machine generated

    and often active HTML pages.

    They were meant for direct human processing (reading, browsing, form-filling).

    The current web=syntactic web A place where computers do the presentation (easy) and

    people do the linking and interpreting (hard).

    The third generation Web= "Semantic Web", aims at machine processable information.

    8

  • Why semantic web?

    The fact that accurate Natural Language Processing (NLP) is not yet achievable in general domains, has led to numerous efforts

    to create standardized semantic languages for the web.

    The semantic web aims

    to create content which both humans and machines can understand

    9

  • The main intent of the Semantic

    Web

    to give machines much better access to information resources

    to improve the existing web with a semantic layer that allows machines to understand it

    to enable software programs to process information efficiently

    Moving from a Web of "finding things" to a Web of "doing things"

    10

  • solution=XML?

    HTML :

    a markup language for a specific kind of hypertext documents.

    Is not extensiable

    XML :

    a markup language for arbitrary document structure,

    Simplifies the process of defining and using metadata.

    Is a meta language: provides a basic structure and a set of rules for developing other languages.

    An XML document consists of a properly nested set of open and close tags, where each tag can have a number of attribute-value pairs.

    11

  • solution=XML?

    12

  • XML document = labelled tree

    why not use XML to represent semantics?

    13

  • Solution:

    XML markup with meaningful tags? WWW2002 The eleventh inteqnational woqld wide webcon Sheqaton waikiki hotel Honolulu, hawaii, USA 7-11 may 2002 1 location 5 days leaqn inteqact Registeqed paqticipants coming fqom austqalia, canada, chile denmaqk, fqance,

    geqmany, ghana, hong kong, india, iqeland,

    italy, japan, malta, new zealand, the

    netheqlands, noqway, singapoqe, switzeqland,

    the united kingdom, the united states,

    vietnam, zaiqe Registeq now On the 7

    th May Honolulu will pqovide the

    backdqop of the eleventh inteqnational woqld

    wide web confeqence. This pqestigious event

    Speakeqs confiqmed Tim beqneqs-lee Tim is the well known inventoq of the Web,

    14

  • Still the Machine only sees

    WWW2002

    The eleventh inteqnational woqld wide webc

    Sheqaton waikiki hotel

    Honolulu, hawaii, USA

    7-11 may 2002

    1 location 5 days leaqn inteqact

    Registeqed paqticipants coming fqom

    austqalia, canada, chile denmaqk, fqance, g

    eqmany, ghana, hong kong, india, iqeland,

    italy, japan, malta, new zealand, the net

    heqlands, noqway, singapoqe, switzeqland, the

    united kingdom, the united states, vietnam,

    zaiqe

    Registeq now

    On the 7th May Honolulu will pqovide the backdq

    op of the eleventh inteqnational woqld wide w

    eb confeqence. This pqestigious event

    Speakeqs confiqmed

    Tim beqneqs-lee

    Tim is the well known inventoq of the W

    Ian Fosteq

    Ian is the pioneeq of the Gqid, the ne

    15

  • Disadvantages of XML

    XML tags can add meaning to data

    Understanding the tags is only meaningful to humans.

    does not impose any common interpretation of the data contained in the document.

    XML is aiming at the structure of documents

    XML just describes grammars

    the vocabulary of the tags and their allowed combinations is not fixed

    16

  • "The author of the page is Ora".

    Ora

    href="page" Ora

    href="page" Ora

    17

  • The complexity of querying the

    XML tree the query you write has to be independent

    of the choice of them.

    Must convert the set of all possible representations of a fact into one statement

    A standard ways of writing statements ?

    RDF The same RDF tree results from many XML trees.

    18

  • RDF

    Resource Description Framework

    a language used for representing information about resources on the web.

    a basic ontology language.

    Motivation:

    to provide a standard for meta-data, for descriptions about resources on the web.

    19

  • The basic construction in RDF

    an object-attribute-value triple: an object O has an attribute A with value V. commonly written as A(O,V)

    A subject, predicate and object triple

    Resource, Property, and Property value triple Resource = anything that can have a URI, such as

    "http://www.w3schools.com/RDF"

    Property = a Resource that has a name, such as "author" or "homepage"

    Property value = the value of a Property, such as

    "Jan Egil " or "http://www.w3schools.com" (note that a property value can be another resource)

    20

  • RDF Statements example a Resource, a Property, and a Property value

    = a subject, predicate and object

    "The author of http://www.w3schools.com/RDF is

    Jan Egil Refsnes".

    The subject ? http://www.w3schools.com/RDF The predicate? author The object ? Jan Egil Refsnes

    22

  • 23

  • RDF Syntax

    RDF has an XML syntax that has a specific meaning:

    Every Description element describes a resource

    Every attribute or nested element inside a Description is a property

    of that Resource

    We can refer to resources by using URIs

    http://www.cs.mam.ac.uk/~sattler

    24

  • RDF Schema=RDFS an object-oriented modelling language

    RDF :provides a model for describing information

    The semantics (meaning of the informations) is described using RDFS.

    RDF Schema semantically extends RDF to enable us

    to talk about classes of resources, and the properties that will be used with them.

    It allows you to define classes

    It allows you to define relationships between classes

    It allows you to define properties of classes

    RDFS = RDF Vocabulary Definition Language

    25

  • RDFS Example

    There is a relationship between Stream and BodyOfWater

    The relationsh