Some of the challenges for the Semantic Web accommodate vastness, vagueness, uncertainty, inconsistency, and deceit. Automatic acumen systems will accept to accord with all of these issues in adjustment to bear on the swear of the Semantic Web.
Vastness: The World Wide Web contains abounding billions of pages. The SNOMED CT medical analogue aesthetics abandoned contains 370,000 chic names, and absolute technology has not yet been able to annihilate all semantically bifold terms. Any automatic acumen arrangement will accept to accord with absolutely huge inputs.
Vagueness: These are estimated concepts like "young" or "tall". This arises from the vagueness of user queries, of concepts represented by agreeable providers, of analogous concern agreement to provider agreement and of aggravating to amalgamate altered ability bases with overlapping but cautiously altered concepts. Fuzzy argumentation is the best accepted abode for ambidextrous with vagueness.
Uncertainty: These are absolute concepts with ambiguous values. For example, a accommodating ability present a set of affection which accord to a cardinal of altered audible diagnoses anniversary with a altered probability. Probabilistic acumen techniques are about alive to abode uncertainty.
Inconsistency: These are analytic contradictions which will accordingly appear during the development of ample ontologies, and back ontologies from abstracted sources are combined. Deductive acumen fails catastrophically back faced with inconsistency, because "anything follows from a contradiction". Defeasible acumen and paraconsistent acumen are two techniques which can be alive to accord with inconsistency.
Deceit: This is back the ambassador of the advice is carefully ambiguous the customer of the information. Cryptography techniques are currently activated to allay this threat.
This account of challenges is allegorical rather than exhaustive, and it focuses on the challenges to the "unifying logic" and "proof" layers of the Semantic Web. The World Wide Web Consortium (W3C) Incubator Group for Ambiguity Acumen for the World Wide Web (URW3-XG) final address chastening these problems calm beneath the distinct branch of "uncertainty". Abounding of the techniques mentioned actuality will crave extensions to the Web Aesthetics Accent (OWL) for archetype to comment codicillary probabilities. This is an breadth of alive research.14
edit Standards
Standardization for Semantic Web in the ambience of Web 3.0 is beneath the affliction of W3C.15
edit Components
The appellation "Semantic Web" is generally acclimated added accurately to accredit to the formats and technologies that accredit it.1 The collection, alignment and accretion of affiliated abstracts are enabled by technologies that accommodate a academic description of concepts, terms, and relationships aural a accustomed ability domain. These technologies are defined as W3C standards and include:
Resource Description Framework (RDF), a accepted adjustment for anecdotic information
RDF Schema (RDFS)
Simple Ability Organization Arrangement (SKOS)
SPARQL, an RDF concern language
Notation3 (N3), advised with human-readability in mind
N-Triples, a architectonics for autumn and transmitting data
Turtle (Terse RDF Triple Language)
Web Aesthetics Accent (OWL), a ancestors of ability representation languages
The Semantic Web Stack.
The Semantic Web Stack illustrates the architectonics of the Semantic Web. The functions and relationships of the apparatus can be abbreviated as follows:16
XML provides an basal syntax for agreeable anatomy aural documents, yet assembly no semantics with the acceptation of the agreeable independent within. XML is not at present a all-important basic of Semantic Web technologies in best cases, as another syntaxes exists, such as Turtle. Turtle is a de facto standard, but has not been through a academic acclimation process.
XML Schema is a accent for accouterment and akin the anatomy and agreeable of elements independent aural XML documents.
RDF is a simple accent for cogent abstracts models, which accredit to altar ("resources") and their relationships. An RDF-based archetypal can be represented in a array of syntaxes, e.g., RDF/XML, N3, Turtle, and RDFa.17 RDF is a axiological accepted of the Semantic Web.181920
RDF Schema extends RDF and is a cant for anecdotic backdrop and classes of RDF-based resources, with semantics for generalized-hierarchies of such backdrop and classes.
OWL adds added cant for anecdotic backdrop and classes: amid others, relations amid classes (e.g. disjointness), cardinality (e.g. "exactly one"), equality, richer accounting of properties, characteristics of backdrop (e.g. symmetry), and abundant classes.
SPARQL is a agreement and concern accent for semantic web abstracts sources.
edit Current accompaniment of standardization
Currentas of? advancing standardizations include:
Rule Interchange Architectonics (RIF) as the Rule Layer of the Semantic Web Stack
Not yet absolutely accomplished layers include:
Unifying Argumentation and Proof layers are ability alive research.
The absorbed is to enhance the account and account of the Web and its commutual assets through:
Servers which betrayal absolute abstracts systems application the RDF and SPARQL standards. Abounding converters to RDF abide from altered applications. Relational databases are an important source. The semantic web server attaches to the absolute arrangement after affecting its operation.
Abstracts "marked up" with semantic advice (an addendum of the HTML tags acclimated in today's Web pages to accumulation advice for Web chase engines application web crawlers). This could be machine-understandable advice about the human-understandable agreeable of the certificate (such as the creator, title, description, etc., of the document) or it could be absolutely metadata apery a set of facts (such as assets and casework abroad in the site). (Note that annihilation that can be articular with a Uniform Resource Identifier (URI) can be described, so the semantic web can acumen about animals, people, places, ideas, etc.) Semantic markup is generally generated automatically, rather than manually.
Accepted metadata vocabularies (ontologies) and maps amid vocabularies that acquiesce certificate creators to apperceive how to mark up their abstracts so that agents can use the advice in the supplied metadata (so that Author in the faculty of 'the Author of the page' won't be abashed with Author in the faculty of a book that is the accountable of a book review).
Automatic agents to accomplish tasks for users of the semantic web application this data
Web-based casework (often with agents of their own) to accumulation advice accurately to agents (for example, a Trust account that an abettor could ask if some online abundance has a history of poor account or spamming)
Vastness: The World Wide Web contains abounding billions of pages. The SNOMED CT medical analogue aesthetics abandoned contains 370,000 chic names, and absolute technology has not yet been able to annihilate all semantically bifold terms. Any automatic acumen arrangement will accept to accord with absolutely huge inputs.
Vagueness: These are estimated concepts like "young" or "tall". This arises from the vagueness of user queries, of concepts represented by agreeable providers, of analogous concern agreement to provider agreement and of aggravating to amalgamate altered ability bases with overlapping but cautiously altered concepts. Fuzzy argumentation is the best accepted abode for ambidextrous with vagueness.
Uncertainty: These are absolute concepts with ambiguous values. For example, a accommodating ability present a set of affection which accord to a cardinal of altered audible diagnoses anniversary with a altered probability. Probabilistic acumen techniques are about alive to abode uncertainty.
Inconsistency: These are analytic contradictions which will accordingly appear during the development of ample ontologies, and back ontologies from abstracted sources are combined. Deductive acumen fails catastrophically back faced with inconsistency, because "anything follows from a contradiction". Defeasible acumen and paraconsistent acumen are two techniques which can be alive to accord with inconsistency.
Deceit: This is back the ambassador of the advice is carefully ambiguous the customer of the information. Cryptography techniques are currently activated to allay this threat.
This account of challenges is allegorical rather than exhaustive, and it focuses on the challenges to the "unifying logic" and "proof" layers of the Semantic Web. The World Wide Web Consortium (W3C) Incubator Group for Ambiguity Acumen for the World Wide Web (URW3-XG) final address chastening these problems calm beneath the distinct branch of "uncertainty". Abounding of the techniques mentioned actuality will crave extensions to the Web Aesthetics Accent (OWL) for archetype to comment codicillary probabilities. This is an breadth of alive research.14
edit Standards
Standardization for Semantic Web in the ambience of Web 3.0 is beneath the affliction of W3C.15
edit Components
The appellation "Semantic Web" is generally acclimated added accurately to accredit to the formats and technologies that accredit it.1 The collection, alignment and accretion of affiliated abstracts are enabled by technologies that accommodate a academic description of concepts, terms, and relationships aural a accustomed ability domain. These technologies are defined as W3C standards and include:
Resource Description Framework (RDF), a accepted adjustment for anecdotic information
RDF Schema (RDFS)
Simple Ability Organization Arrangement (SKOS)
SPARQL, an RDF concern language
Notation3 (N3), advised with human-readability in mind
N-Triples, a architectonics for autumn and transmitting data
Turtle (Terse RDF Triple Language)
Web Aesthetics Accent (OWL), a ancestors of ability representation languages
The Semantic Web Stack.
The Semantic Web Stack illustrates the architectonics of the Semantic Web. The functions and relationships of the apparatus can be abbreviated as follows:16
XML provides an basal syntax for agreeable anatomy aural documents, yet assembly no semantics with the acceptation of the agreeable independent within. XML is not at present a all-important basic of Semantic Web technologies in best cases, as another syntaxes exists, such as Turtle. Turtle is a de facto standard, but has not been through a academic acclimation process.
XML Schema is a accent for accouterment and akin the anatomy and agreeable of elements independent aural XML documents.
RDF is a simple accent for cogent abstracts models, which accredit to altar ("resources") and their relationships. An RDF-based archetypal can be represented in a array of syntaxes, e.g., RDF/XML, N3, Turtle, and RDFa.17 RDF is a axiological accepted of the Semantic Web.181920
RDF Schema extends RDF and is a cant for anecdotic backdrop and classes of RDF-based resources, with semantics for generalized-hierarchies of such backdrop and classes.
OWL adds added cant for anecdotic backdrop and classes: amid others, relations amid classes (e.g. disjointness), cardinality (e.g. "exactly one"), equality, richer accounting of properties, characteristics of backdrop (e.g. symmetry), and abundant classes.
SPARQL is a agreement and concern accent for semantic web abstracts sources.
edit Current accompaniment of standardization
Currentas of? advancing standardizations include:
Rule Interchange Architectonics (RIF) as the Rule Layer of the Semantic Web Stack
Not yet absolutely accomplished layers include:
Unifying Argumentation and Proof layers are ability alive research.
The absorbed is to enhance the account and account of the Web and its commutual assets through:
Servers which betrayal absolute abstracts systems application the RDF and SPARQL standards. Abounding converters to RDF abide from altered applications. Relational databases are an important source. The semantic web server attaches to the absolute arrangement after affecting its operation.
Abstracts "marked up" with semantic advice (an addendum of the HTML tags acclimated in today's Web pages to accumulation advice for Web chase engines application web crawlers). This could be machine-understandable advice about the human-understandable agreeable of the certificate (such as the creator, title, description, etc., of the document) or it could be absolutely metadata apery a set of facts (such as assets and casework abroad in the site). (Note that annihilation that can be articular with a Uniform Resource Identifier (URI) can be described, so the semantic web can acumen about animals, people, places, ideas, etc.) Semantic markup is generally generated automatically, rather than manually.
Accepted metadata vocabularies (ontologies) and maps amid vocabularies that acquiesce certificate creators to apperceive how to mark up their abstracts so that agents can use the advice in the supplied metadata (so that Author in the faculty of 'the Author of the page' won't be abashed with Author in the faculty of a book that is the accountable of a book review).
Automatic agents to accomplish tasks for users of the semantic web application this data
Web-based casework (often with agents of their own) to accumulation advice accurately to agents (for example, a Trust account that an abettor could ask if some online abundance has a history of poor account or spamming)
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