--- pl:dydaktyka:semweb:lab-rdf1 [2019/06/27 15:50]
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+====== Resource Description Framework (RDF) ======
+===== Before the lab =====
+Reading:
+  * [[http://w3schools.com/rdf/default.asp|RDF at W3Schools]]
+  * [[http://dublincore.org/documents/dc-rdf/|Expressing Dublin Core metadata using the Resource Description Framework (RDF)]]
+  * [[http://www.betaversion.org/~stefano/linotype/news/57/|A No-Nonsense Guide to Semantic Web Specs for XML People]]
+  * [[#if_you_want_to_know_more|If you want to know more...]]
+Software:
+  * [[http://semweb.salzburgresearch.at/apps/rdf-gravity|RDF Gravity]]
+===== Introduction =====
+Lecture:
+  * {{http://home.agh.edu.pl/wta/semweb/geist-semweb-rdf.pdf|Semantic Web: 3a - RDF}}
+  * {{http://home.agh.edu.pl/wta/semweb/geist-semweb-rdfsutils.pdf|Semantic Web: 3b - RDF/S in use}}
+  * {{http://home.agh.edu.pl/wta/semweb/geist-semweb-rdfs.pdf|Semantic Web: 3c - RDF Schema}}
+===== Lab instructions =====
+The lab is divided into sections. You should allow aprox. 10 minutes for each section.
+However, note that the tasks are increasingly difficult and latter sections may be more time-consuming than the former ones.
+==== - RDF model ====
+  * RDF model is a directed graph built from ''Statements''
+  * Each Statement consists of: ''<subject>'', ''<predicate>'' and ''<object>''
+    * Subject can be an //URI// or an //empty node//
+    * Predicate can be an //URI//
+    * Object can be an //URI//, an //empty node// or a //literal//
+  - Go to [[http://www.w3.org/RDF/Validator/|W3C's RDF Validation Service]]
+    - In section "Check by Direct Input" set **Display Result Options** to: ''Triples and Graph'' and click ''Parse RDF''. Analyze the RDF/XML code and the graphical representation. {{:pl:dydaktyka:semantic_web:rdf-validator1.png?200|}}
+    - In section "Check by URI" paste the following URI: ''http://home.agh.edu.pl/~wta/foaf.rdf''. Analyze the RDF/XML code and the graphical representation. {{:pl:dydaktyka:semantic_web:rdf-validator2.png?200|}}
+==== - RDF document: basics ====
+RDF document is an RDF graph (describing some objects) serialized into chosen representation/syntax.
+Here we will use the RDF/XML syntax for RDF.
+Your task will be to create an RDF description of you multimedia library.
+It can contain CDs, DVDs, books etc.
+The documents created during this lab will be used in the subsequent labs.
+a) Create a text document and save it as ''mylibrary.rdf''.
+<code xml>
+<?xml version="1.0" encoding="UTF-8"?>
+<rdf:RDF
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+   <!-- Body Code Omitted -->
+</rdf:RDF>
+</code>
+NB: Note the '' http://www.w3.org/1999/02/22-rdf-syntax-ns#'' namespace used in the document.
+b) Add statements: Add RDF statements about items in your multimedia library, e.g.:
+<code xml>
+<rdf:RDF
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+   <rdf:Description rdf:about="http://example.org/mylibrary#book-semwebprimer">
+		<!-- Statement Code Omitted -->
+   </rdf:Description>
+   <rdf:Description rdf:about="http://example.org/mylibrary#cd-opeth_damnation">
+		<!-- Statement Code Omitted -->
+   </rdf:Description>
+</rdf:RDF>
+</code>
+The ''rdf:Description'' tag means you're going to describe something (a subject) and giving it a unique ID: ''http://example.org/mylibrary#your-book-id''.
+c) Add predicates: define some //properties// of the items and fill in their //values//, e.g.:
+<code xml>
+<rdf:RDF
+	xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+        xmlns="http://example.org/mylibrary#">
+   <rdf:Description rdf:about="http://example.org/mylibrary#book-semwebprimer">
+     <author>Grigoris Antoniou</author>
+     <author>Frank van Harmelen</author>
+     <title>A Semantic Web Primer</title>
+   </rdf:Description>
+   <rdf:Description rdf:about="http://example.org/mylibrary#cd-opeth_damnation">
+     <artist>Opeth</artist>
+     <title>Damnation</title>
+   </rdf:Description>
+</rdf:RDF>
+</code>
+Define your namespace (see the 3. line).
+==== - RDF document: Containers and Collections ====
+In RDF there are two ways to describe set or sequences of objects: //Containters// and //Collections//.
+  - According to the [[http://www.w3.org/TR/rdf-syntax/#containers|W3C Recommendation]], "A container is a resource that contains things. The contained things are called members. The members of a container may be resources (including blank nodes) or literals. RDF defines three types of containers:
+    * ''rdf:Bag''
+    * ''rdf:Seq''
+    * ''rdf:Alt''"
+  - Create a container called ''MyFavouriteBooks'' and fill it with the URIs of the books you like the most. (see [[http://www.w3.org/TR/rdf-syntax/#containers|here]] for hints and examples)
+  - While "a container only says that certain identified resources are members; it does not say that other members do not exist." with a //Collection// we can describe groups containing __only__ the specified members. "An RDF collection is a group of things represented as a list structure in the RDF graph."
+  - In your RDF file describe a book/CD/DVD which has multiple authors or actors playing in it. Use the //RDF Collection//. For hint and examples see the [[http://www.w3.org/TR/rdf-syntax/#collections|recommendation]].
+==== - RDF document: Datatypes ====
+Add the references to [[http://www.w3.org/TR/xmlschema-2/|XML Schema datatypes]] to chosen information in your RDF file, e.g.:
+<code xml>
+<rdf:Description rdf:about="http://example.org/mylibrary#book-semwebprimer">
+  <author>Grigoris Antoniou</author>
+  <author>Frank van Harmelen</author>
+  <title rdf:datatype="http://www.w3.org/2001/XMLSchema#string">A Semantic Web Primer</title>
+  <publicationDate rdf:datatype="http://www.w3.org/2001/XMLSchema#date">2008-10-09</publicationDate>
+</rdf:Description>
+</code>
+==== - RDF Triples Validation and Visualization ====
+  - Validate your example on the page [[http://www.w3.org/RDF/Validator//| RDF Validator from w3.org]] and analyze generated graph. Correct the errors, if you made any.
+  - Open your file in [[http://semweb.salzburgresearch.at/apps/rdf-gravity|RDF Gravity]] tool. Browse your multimedia library using different filters.
+==== - RDFSchema ====
+RDF Schema allows to organize objects into classes, define simple taxonomies, as well as classes' domains and ranges.
+  - Define classes of items in you multimedia library, e.g.
+<code xml>
+<rdf:RDF
+  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+  xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
+  xml:base="http://example.org/mylibrary#">
+  <rdfs:Class rdf:ID="MultimediaItem" />
+  <rdfs:Class rdf:ID="MusicCD">
+    <rdfs:subClassOf rdf:resource="#MultimediaItem"/>
+    <rdfs:label>Music Compact Discs class</rdfs:label>
+    <rdfs:comment>Class of all the CDs in my library.</rdfs:comment>
+  </rdfs:Class>
+  <rdfs:Class rdf:ID="Book">
+    <rdfs:subClassOf rdf:resource="#MultimediaItem"/>
+  </rdfs:Class>
+</rdf:RDF>
+</code>
+Add the ''rdf:type'' statements to your RDF file, e.g.:
+<code xml>
+<rdf:Description rdf:about="http://example.org/mylibrary#cd-opeth_damnation">
+  <artist>Opeth</artist>
+  <title>Damnation</title>
+  <rdf:type rdf:resource="http://example.org/mylibrary#MusicCD"/>
+</rdf:Description>
+</code>
+==== - RDF/S vocabularies: Dublin Core ====
+Semantic vocabularies are sets of predefined properties for describing some domains. Examples include:
+  * [[http://semanticweb.org/wiki/Dublin_Core|Dublin Core]]
+  * [[http://semanticweb.org/wiki/FOAF|FOAF]]
+  * [[http://semanticweb.org/wiki/RSS_1.0|RSS 1.0]]
+  * [[http://semanticweb.org/wiki/SIOC|SIOC]]
+  * etc.
+  - Have a look at [[http://www.w3schools.com/rdf/rdf_dublin.asp|Dublin Core basics at W3Schools]].
+  - Modify your RDF/S file to use the properties from DublinCore vocabulary, e.g.:
+<code xml>
+<rdf:Description rdf:about="http://example.org/mylibrary#book-semwebprimer">
+  <author>Grigoris Antoniou</author>
+  <author>Frank van Harmelen</author>
+  <dc:title rdf:datatype="http://www.w3.org/2001/XMLSchema#string">A Semantic Web Primer</dc:title>
+  <dc:date rdf:datatype="http://www.w3.org/2001/XMLSchema#date">2008-10-09</dc:date>
+  <dc:publisher>The MIT Press</dc:publisher>
+  <dc:language>en</dc:language>
+</rdf:Description>
+</code>
+    * Hint: use the explanation and examples from [[http://dublincore.org/documents/dcmes-xml/|the basic (superseeded) version of DC]] or, if you are more ambitious, read the latest, enhanced [[http://dublincore.org/documents/dc-rdf/|version]].
+==== - RDF/S vocabularies: FOAF ====
+[[http://www.foaf-project.org/|FOAF]] (Friend-of-a-friend) is a semantic vocabulary for describing people and their connections.
+  - Create your FOAF file with: [[http://www.ldodds.com/foaf/foaf-a-matic|foaf-o-matic]].
+  - Save you FOAF file.
+  - Put the file on a server (e.g. ''student.agh.edu.pl'') so that it can be referenced with URL.
+  - Put the link to your FOAF file [[#foaf_files_of_piw_2011|here]] (log in with username ''piw2011'', for password ask the teacher):
+  - Visualize it with: [[http://xml.mfd-consult.dk/foaf/explorer/|FOAF explorer]]
+  - Add more friends using their FOAF URIs in the ''<foaf:knows>'' section. Visualize again. Navigate to your friends' FOAF files.
+  * (example) Weronika T. Adrian: http://home.agh.edu.pl/~wta/foaf.rdf
+===== Control questions =====
+   * What are:
+       * resources,
+       * properties,
+       * statemets.
+   * What does RDF use to identify resources?
+   * What are the required elements of RDF file?
+   * What are namespaces, how are they defined and what are they used for?
+   * What the following tags are used for:
+       * ''<rdf:Description>''
+       * ''<rdf:about>''
+       * ''<rdf:resource>''
+       * ''<rdf:type>''
+   * What container elements are available in RDF?
+   * What is RDF Schema?
+   * What are core RDFS Classes and properties?
+   * How constraints on domain and range of properties are added?
+===== If you want to know more =====
+Reading:
+  * RDF Primer, W3C Recommendation 10-02-2004: http://www.w3.org/TR/rdf-primer/
+  * http://www.w3.org/DesignIssues/RDFnot.html
+  * RDF interfaces, Working Draft 11-05-2011: http://www.w3.org/TR/rdf-interfaces/
+Slides:
+  * [[ http://www.inf.unibz.it/~debruijn/teaching/swt/lecture-1-handouts.pdf|RDF ]] and [[http://www.inf.unibz.it/~debruijn/teaching/swt/lecture-2-handouts.pdf|RDFS]]
+  * [[http://www.cs.rpi.edu/~puninj/XMLJ/classes/class8/all.html| RDF and RDFS summary]]
+Tools:
+  * http://jena.sourceforge.net/tutorial/RDF_API/

pl/dydaktyka/semweb/lab-rdf1.txt · ostatnio zmienione: 2019/06/27 15:50 (edycja zewnętrzna)

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