Answers for Practice Number 3

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Claire Lewis
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1 RDFS-Exercise 1. Answers for Practice Number 3 Give a graphical presentation and RDF Schema that describe the following: Professors and assistants are subclasses of teachers. Each techer has a name. Each course has a course_id. Professors lecture courses while assistants suprervise courses. Course supervises Assistant teacher_name subclassof course_id lectures Teacher Literal Literal subclassof Professor

2 <rdf : RDF xmlns : rdf= xmlns : rdfs= > <rdfs:class rdf:id= assistant > <rdfs:comment>the class of assistants.</rdfs:comment> <rdfs:subclassof rdf:resource= teacher /> </rdfs:class> <rdfs:class rdf:id= professor > <rdfs:comment>the class of professors.</rdfs:comment> <rdfs:subclassof rdf:resource= teacher /> </rdfs:class> <rdfs:class rdf:id= teacher > <rdfs:comment>the class of teachers</rdfs:comment> </rdfs:class> <rdfs:class rdf:id= course > <rdfs:comment>the class of courses</rdfs:comment> </rdfs:class>

3 <rdfs:property rdf:id= lectures > <rdfs:comment> It relates professors to courses </rdfs:comment> <rdfs: rdf:resource= #professor /> <rdfs: rdf:resource= #course /> </rdfs:property> <rdfs:property rdf:id= supervises > <rdfs:comment> It relates assistants to courses </rdfs:comment> <rdfs: rdf:resource= #assistant /> <rdfs: rdf:resource= #course /> </rdfs:property>

4 </rdf:rdf> <rdfs:property rdf:id= lecturer_name > <rdfs:comment> It is a property of teachers and takes literals as values. </rdfs:comment> <rdfs: rdf:resource= #teacher /> <rdfs: rdf:resource= &rdf;literal /> </rdfs:propert> <rdfs:property rdf:id= course_id > <rdfs:comment> It is a property of courses and takes literals as values. </rdfs:comment> <rdfs: rdf:resource= #course /> <rdfs: rdf:resource= &rdf;literal /> </rdfs:propert>

5 Execise 2. RQL-Exercise. By using RQL and the RDF Schema of the previous exercise give the following queries: a) Retrieve all the instances of the class Teacher b) Retrieve aal the inatances of the class Teacher that are iether profwssors or assistanra. c) Retrieve the names of the assistants. Answers: a) teacher b) ^teacher c) select X, Y from assistant{x}. teacher_name {Y}

6 Execise 3. Discuss the difference vbetween the following statements, and draw graphs to illustrate the difference: X supports the proposal; Y supports the propodsal; Z supports the proposal. The group of X, Y, and Z supports the proposal. Draw graphs to illustrate the difference. X Y Z supports supports supports the proposal the proposal the proposal

7 X belongs Y belongs the group supports the proposal belongs Z

8 Exercise 4. Compare rdfs:subclassof with type extension in XML Schema

9 Exercise 5. Try to map the relational database model on RDF.

10 Exercise 6. Compare entity-relationship modelling to RDF.

11 Exercise 7.Model part of a library in RDF Schema: books, authors, publishers, years, copies, dates, and so on. Then write some statements in RDF, and query them using RQL. literal year Author ISBN literal writtenby Book publishedby presents Copy literal publishretname Publisher copynumber literal

12 <rdf:rdf xmlns:rdf= http.w3.org/1999/02/22-rdf-syntax-ns# xmlns:rdfs= http.w3.org/2000/01/rdf-schema# > <rdfs:class rdf:id= book > <rdfs:comment>the class of books</rdfs:comment> </rdfs:class> <rdfs:class rdf:id= publisher > <rdfs:comment>the class of publishers</rdfs:comment> </rdfs:class> <rdfs:property rdf:id= publishedby > <rdfs:comment> It relates books to publishers </rdfs:comment> <rdfs: rdf:resource= #book /> <rdfs: rdf:resource= #publisher /> </rdfs:property>

13 <rdfs:property rdf:id= ISBN > <rdfs:comment> It is a property of books and takes literals as values. </rdfs:comment> <rdfs: rdf:resource= #book /> <rdfs: rdf:resource= &rdf;literal /> </rdfs:propert> </rdf:rdf>

14 RDF-statements <my: book rdf:id= my: ISBN = abc567 > <my: publishedby rdf:resource= #Prenticee_Hall /> <my: writternby rdf:resourcre= #Jack_Smith /> </my:book> The same RDF-description by not using abbreviated syntax <rdf: Description rdf: ID= > <rdf : type rdf : resource= &my ; book /> <my : ISBN> abc567 </my : ISBN> <my: publishedby rdf:resource= #Prenticee_Hall /> <my: writternby rdf:resourcre= #Jack_Smith /> </rdf : Description>

15 Queries: a) Retrieve all the instances of the book class? Anwer: book b) Retrieve all books and their ISBN:s: Answer: select X, Y from book {X}. ISBN {y} c) Retrieve all the ISBN:s of the books published by Prentice-Hall Answer: select N from book {X}. publishedby {Y}, {C} ISBN {N} where Y= Prentice-Hall and X=C

RDF Schema. Mario Arrigoni Neri

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