Changes between Version 28 and Version 29 of SemanticWebServices

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2009/03/20 11:19:52 (16 years ago)
Author:
luke
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  • SemanticWebServices

    v28 v29  
    3838==== RDF ==== 
    3939[http://www.w3.org/RDF/ RDF] assumes that anything in the world can be described in triples, i.e. statements consisting of subject, predicate, object. [http://www.w3.org/TR/rdf-syntax-grammar/ RDF/XML] is just one serialization of the concept of triples (other ways are [http://www.w3.org/DesignIssues/Notation3 N3], [http://www.json.org/ JSON], [http://www.w3.org/TR/rdfa-syntax/ RDFa] etc.). An RDF/XML document imports at least two namespaces: rdf and [http://www.w3.org/TR/rdf-schema/ rdfs].  
    40  * Simple example: rdf:Description element defines the subject, rdf:about attribute defines a resource that is the subject. rdfs:label, for example, attaches a human readable label to a subject. 
    41  * Example with more namespaces: subject is now defined on element foaf:Person (again by rdf:about), subject has multiple predicates: foaf:name (his name), foaf:page (which in turn encloses another triple: foaf:Document => dc:title => literal) 
     40  * Simple example: rdf:Description element defines the subject, rdf:about attribute defines a resource that is the subject. rdfs:label, for example, attaches a human readable label to a subject. 
     41 
     42XML representation of RDF: 
     43{{{ 
     44<rdf:RDF 
     45    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 
     46    xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"> 
     47 
     48        <rdf:Description rdf:about="http://elmonline.ca/luke"> 
     49                <rdfs:label>Luke McCarthy's web page</rdfs:label> 
     50        </rdf:Description> 
     51 
     52</rdf:RDF> 
     53}}} 
     54 
     55Expanded human-readable representation: 
     56subject: <http://elmonline.ca/luke> 
     57predicate: 'rdfs:label' => <http://http://www.w3.org/2000/01/rdf-schema#label> 
     58object: "Luke McCarthy's web page" 
     59 
     60Condensed human-readable representation: 
     61<http://elmonline.ca/luke> <http://www.w3.org/2000/01/rdf-schema#label>  "Luke McCarthy's blog" 
     62 
     63 * Example with more namespaces: subject is now defined on element foaf:Person (again by rdf:about), subject has multiple predicates: foaf:name (his name), foaf:page (which in turn encloses another object: foaf:Document => dc:title => literal) 
     64 
     65XML representation of RDF: 
     66{{{ 
     67<rdf:RDF 
     68  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 
     69  xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" 
     70  xmlns:foaf="http://xmlns.com/foaf/0.1/" 
     71  xmlns:dc="http://purl.org/dc/elements/1.1/"> 
     72 
     73  <foaf:Person rdf:about="http://sw.elmonline.ca/luke"> 
     74    <foaf:name>Luke McCarthy</foaf:name> 
     75    <foaf:page> 
     76      <foaf:Document rdf:about="http://elmonline.ca/luke"> 
     77        <dc:title>Luke McCarthy's web page</dc:title> 
     78      </foaf:Document> 
     79    </foaf:page> 
     80  </foaf:Person> 
     81 
     82</rdf:RDF> 
     83}}} 
     84 
     85Condensed human-readable representation: 
     86<http://sw.elmonline.ca/luke> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>  <http://xmlns.com/foaf/0.1/Person> . 
     87<http://sw.elmonline.ca/luke> <http://xmlns.com/foaf/0.1/name>  "Luke McCarthy" . 
     88<http://sw.elmonline.ca/luke> <http://xmlns.com/foaf/0.1/page>  <http://elmonline.ca/luke> . 
     89<http://elmonline.ca/luke> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>  <http://xmlns.com/foaf/0.1/Document> . 
     90<http://elmonline.ca/luke> <http://purl.org/dc/elements/1.1/title>  "Luke McCarthy's web page" 
     91 
    4292 * Real example: a set of triples describing Tim Berners-Lee using foaf ([http://www.foaf-project.org/ Friend of a Friend]), dc ([http://dublincore.org/ Dublin core]), rss ([http://en.wikipedia.org/wiki/RSS_(file_format) Really Simple Syndication]), rdfs. 
    43  * Biological example: a !UniProt record 
     93 
     94XML representation of RDF: 
     95{{{ 
     96<rdf:RDF 
     97  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 
     98  xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" 
     99  xmlns:foaf="http://xmlns.com/foaf/0.1/" 
     100  xmlns:dc="http://purl.org/dc/elements/1.1/" 
     101  xmlns:rss="http://purl.org/rss/1.0/" 
     102  xmlns:html="http://www.w3.org/1999/xhtml"> 
     103 
     104  <foaf:Agent rdf:nodeID="id2246148">  
     105    <foaf:name>Tim Berners-Lee</foaf:name>  
     106    <foaf:weblog>  
     107      <foaf:Document rdf:about="http://dig.csail.mit.edu/breadcrumbs/blog/4">  
     108        <dc:title>Tim Berners-Lee</dc:title>  
     109        <rdfs:seeAlso>  
     110          <rss:channel rdf:about="http://dig.csail.mit.edu/breadcrumbs/blog/feed/4">  
     111            <foaf:maker rdf:nodeID="id2246148"/>  
     112            <foaf:topic rdf:resource="http://www.w3.org/2001/sw/"/>  
     113            <foaf:topic rdf:resource="http://www.w3.org/RDF/"/>  
     114          </rss:channel> 
     115        </rdfs:seeAlso>  
     116      </foaf:Document>  
     117    </foaf:weblog>  
     118    <foaf:interest rdf:resource="http://www.w3.org/2001/sw/"/>  
     119    <foaf:interest rdf:resource="http://www.w3.org/RDF/"/>  
     120  </foaf:Agent> 
     121 
     122</rdf:RDF> 
     123}}} 
     124 
     125Condensed human-readable representation: 
     126<id2246148> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>  <http://xmlns.com/foaf/0.1/Agent> . 
     127<id2246148> <http://xmlns.com/foaf/0.1/name>  "Tim Berners-Lee" . 
     128<id2246148> <http://xmlns.com/foaf/0.1/interest>  <http://www.w3.org/RDF/> . 
     129<id2246148> <http://xmlns.com/foaf/0.1/interest>  <http://www.w3.org/2001/sw/> . 
     130<id2246148> <http://xmlns.com/foaf/0.1/weblog>  <http://dig.csail.mit.edu/breadcrumbs/blog/4> . 
     131# this says that there is an Agent named Tim Berners-Lee who is interested in RDF and the Semantic Web and has a weblog (identified by http://dig.csail.mit.edu/breadcrumbs/blog/4) 
     132 
     133<http://dig.csail.mit.edu/breadcrumbs/blog/4> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>  <http://xmlns.com/foaf/0.1/Document> . 
     134<http://dig.csail.mit.edu/breadcrumbs/blog/4> <http://purl.org/dc/elements/1.1/title>  "Tim Berners-Lee" . 
     135# this says that the weblog identified above is a Document titled "Tim Berners-Lee" 
     136 
     137<http://dig.csail.mit.edu/breadcrumbs/blog/4> <http://www.w3.org/2000/01/rdf-schema#seeAlso>  <http://dig.csail.mit.edu/breadcrumbs/blog/feed/4> . 
     138<http://dig.csail.mit.edu/breadcrumbs/blog/feed/4> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>  <http://purl.org/rss/1.0/channel> . 
     139<http://dig.csail.mit.edu/breadcrumbs/blog/feed/4> <http://xmlns.com/foaf/0.1/maker>  <id2246148> . 
     140<http://dig.csail.mit.edu/breadcrumbs/blog/feed/4> <http://xmlns.com/foaf/0.1/topic>  <http://www.w3.org/RDF/> . 
     141<http://dig.csail.mit.edu/breadcrumbs/blog/feed/4> <http://xmlns.com/foaf/0.1/topic>  <http://www.w3.org/2001/sw/> . 
     142# this says that the weblog identified by http://dig.csail.mit.edu/breadcrumbs/blog/4 has an alternative representation (rdfs:seeAlso) that is the RSS feed (rss:channel) identified by http://dig.csail.mit.edu/breadcrumbs/blog/feed/4.  This feed is about RDF and the Semantic Web and is written by the Agent above (Tim Berners-Lee) 
     143 
     144 * Biological example: a !UniProt record: [http://www.uniprot.org/uniprot/P47989.rdf http://www.uniprot.org/uniprot/P47989.rdf] 
    44145==== OWL ==== 
    45146While RDF just defines triples, [http://www.w3.org/TR/owl-features/ OWL] (Web Ontology Language) allows for defining classes of things, as opposed to opaque resources, for subjects (class), predicates (property) and objects (class). The previous examples that included things such as foaf:Person were using instances of classes from OWL ontologies.