02: Describing Web Sources in RDF Flashcards

1
Q

RDF

A
  • Resource Description Framework
  • framework for describing resources on the web
  • designed to be read and understood by computers
  • not designed for being displayed to people
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2
Q

Drawbacks of XML

A
  • does not talk about semantics (meaning) of data
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3
Q

Basic Building Block of RDF

A
  • object-attribute-value triplet
    • also called a statement
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4
Q

Fundamental Concepts of RDF

A
  • resources
  • properties
  • statements
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5
Q

Resources

A

Like an object, a “thing” we want to talk about

e.g. authors, books, publishers, places, people, hotels

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6
Q

URI

A

Universal Resource Identifier

i.e. a URL (Uniform Resource Locator), web address, or some other kind of unique identifier

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7
Q

Advantages of Using URIs

A
  • ​Provides a global, worldwide, unique naming scheme
  • Reduce the homonym problem of distributed data representation
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8
Q

Properties

A
  • describe relations between resources
    e. g. “written-by”, “age”, “title”, etc.
  • also identified by URIs
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9
Q

Statements

A
  • assert the properties of resources
  • object-attribute-value triple or subject-predicate-object
    • consists of a resource, a property, and a value
  • values can be resources or literals
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10
Q

The Three Views of a Statement in RDF

A
  • A triple
  • A piece of a graph (e.g. a semantic net)
  • A piece of XML code (e.g. an XML document)
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11
Q

Draw the following triplet as a semantic net:

David Billington owns the website www.cit.gu.edu.au/~db.

A
  • from the resource (the subject of the statement)
  • to the value (the object of the statement)
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12
Q

Write the following statement as XML in an RDF document:

David Billington owns the website www.cit.gu.edu.au/~db.

A
  • rdf:about sets the object URI of a statement
  • rdf:resource sets the value URI of a statement
  • rdf:Description makes a statement about the resource, where the property is used as a tag and the content is the value of the property
  • # in “#David Billington” indicates an ID defined in the same document
  • rdf:RDF is a tag that represents an RDF document
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13
Q

Write the following as a triplet:

X is the referee in a chess game between players Y and Z.

referee(X, Y, Z)

A
  • Introduce new auxiliary resource: chessGame
  • Identify binary predicates: ref, player1, player2

“X referees a chess game.”

“Player X plays in the game.”

“Player Z plays in the game.”

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14
Q

Reification

A

“statements can be made about other statements”

  • rdf:subject, rdf:predicate, and rdf:object allow us to access the parts of a statement
  • The ID of the statement can be used to refer to it, as can be done for any description
  • Write rdf:Description if we don’t want to talk about a statement further
  • Write rdf:Statement if we wish to refer to a statement
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15
Q

Perform reification on the following statement and give it the ID of StatementAbout949352

A
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16
Q

What is the difference between rdf:about and rdf:ID?

A

rdf:about - indicates that the resource has already been “defined” elsewhere

rdf:ID - indicates that the resource is defined now

17
Q

Simplification Rules of RDF

A
  • Childless property elements within description elements may be replaced by XML attributes
  • For description elements with a typing element we can use the name specified in the rdf:type element instead of rdf:Description
18
Q

Abbreviate the following RDF using the simplification rules:

A
19
Q

Container Elements

A
  • number of resources or attributes about which we want to make statements as a whole
    e. g. we may wish to talk about the courses given by a particular lecturer
  • content of container elements are named rdf:_1, rdf:_2, etc.
20
Q

Three Types of Container Elements:

1. rdf:Bag

A

Unordered container, allowing multiple occurrences
e.g. members of the faculty board, documents in a folder

<lecturer></lecturer>

<coursestaught></coursestaught>

<bag></bag>

<_1 rdf:resource=”#CIT1112”>

<_2 rdf:resource=”#CIT3116”>

21
Q

Three Types of Container Elements:

2. rdf:Seq

A

Ordered container, which may contain multiple occurrences
e.g. modules of a course, items on an agenda, an alphabetized list of staff members

  • *
22
Q

Three Types of Container Elements:

3. rdf:Alt

A

A set of alternatives
e.g. translations of a document in various languages