Practical RDF Chapter 4. Specialized RDF Relationships: Reification, Containers, and Collections

Practical RDFChapter 4. Specialized RDF Relationships:Reification, Containers, and CollectionsShelley Powers, O’Reilly

SNU IDB Lab.Hyewon Lim

Outline Containers Collections Reification

2

Containers RDF Containers

– Specifically for handling multiple resources, or for handling multiple literals (properties)

– If you want to refer to the collection of items as a singular unit, you would use the Container

– E.g., A book created by several authors, a list of students in a course

RDF Container vocabulary– Bags– Sequences– Alternative and some associated properties

3

ContainersBag rdf:Bag

– Contains unordered lists of resources or literals– Duplicate data allowed– E.g., inventory of photographs

4

<?xml version=“1.0” ?><rdf:RDF xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns# xmlns:pstcn=http://burningbird.net/postcon/elements/1.0/>

<rdf:Description rdf:about=http://burningbird.net/earthstars/contest.htm> <pstcn:photos> <rdf:Bag> <rdf:li rdf:resource=“http://burningbird.net/earthstars/capo.jpg” /> <rdf:li rdf:resource=“http://burningbird.net/earthstars/baritea.jpg” /> <rdf:li rdf:resource=“http://burningbird.net/earthstars/cfluorite.jpg” /> <rdf:li rdf:resource=“http://burningbird.net/earthstars/ccinnibar.jpg” /> <rdf:li rdf:resource=“http://burningbird.net/earthstars/baryto.jpg” /> <rdf:li rdf:resource=“http://burningbird.net/earthstars/cbarite2a.jpg” /> </rdf:Bag> </pstcn:photos></rdf:Description>

</rdf:RDF>

If the container contained literals instead of resources as items: <rdf:li>Barite Photo</rdf:li>

ContainersSequence rdf:Seq

– Contains ordered list of resources or literals Ordering of the elements is indicated by the ordering of the

rdf:_n

– Duplicate resources or literals are allowed– E.g., web pages within a menu on the main web page

5


<rdf:Description rdf:about=http://burningbird.net/earthstars/contest.htm> <pstcn:menu> <rdf:Seq> <rdf:li rdf:resource=“http://burningbird.net/articles.htm” /> <rdf:li rdf:resource=“http://burningbird.net/dynatech.htm” /> <rdf:li rdf:resource=“http://burningbird.net/interact.htm” /> </rdf:Seq> </pstcn:menu></rdf:Description>

</rdf:RDF>

ContainersAlternative rdf:Alt

– Provides alternatives for a specific value– Must be at least one item to act as the default value for the

resource The first item being the default if no other is specified Other than rdf:_1, the order of the remaining elements is not

significant. The user can select only one of the values

6

<?xml version="1.0"?><rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:cd="http://www.recshop.fake/cd#">

<rdf:Description rdf:about="http://www.recshop.fake/cd/Beatles"> <cd:format> <rdf:Alt> <rdf:li>CD</rdf:li> <rdf:li>Record</rdf:li> <rdf:li>Tape</rdf:li> </rdf:Alt> </cd:format></rdf:Description>

</rdf:RDF>

ContainersContainers as Typed Nodes Can also specify the numbered elements directly or

mix elements

7


<rdf:Description rdf:about=http://burningbird.net/earthstars/contest.htm> <pstcn:menu> <rdf:Seq> <rdf:_1 rdf:resource=“http://burningbird.net/articles.htm” /> <rdf:li rdf:resource=“http://burningbird.net/dynatech.htm” /> <rdf:li rdf:resource=“http://burningbird.net/interact.htm” /> </rdf:Seq> </pstcn:menu></rdf:Description>

</rdf:RDF>

ContainersContainers Today rdf:li

– used and still documented within the RDF specifications The numbered properties rdf:_1, rdf:_2, etc. are generated from

the li elements in forming the corresponding graph– Its use is discouraged within RDF/XML documents

8


<rdf:Description rdf:about=http://burningbird.net/earthstars/contest.htm> <pstcn:menu> <rdf:Seq> <rdf:_1 rdf:resource=“http://burningbird.net/articles.htm” /> <rdf:_2 rdf:resource=“http://burningbird.net/dynatech.htm” /> <rdf:_3 rdf:resource=“http://burningbird.net/interact.htm” /> </rdf:Seq> </pstcn:menu></rdf:Description>

</rdf:RDF>

Valid use of containers

9


Collections (1/2)

rdf:parseType=“Collection”– A finite grouping of items, with a given terminator

– A collection is a list (rdf:List) Each node on the list has an associated predicate of type (List)

as well as the first value in the list, given by the predicate rdf:first

A relationship between the nodes with rdf:rest Terminated with a node, whose value is rdf:nil

10


<rdf:Description rdf:about=http://burningbird.net/earthstars/contest.htm> <pstcn:menu rdf:parseType=“Collection”> <rdf:Description rdf:resource=“http://burningbird.net/articles.htm” /> <rdf:Description rdf:resource=“http://burningbird.net/dynatech.htm” /> <rdf:Description rdf:resource=“http://burningbird.net/interact.htm” /> </pstcn:menu></rdf:Description>

</rdf:RDF>

Collections (2/2)

11

http://dynamicearth.com/earthstars/contest.htm

http://www.w3.org/1999/02/22-rdf-syntax#nil

http://www.w3.org/1999/02/22-rdf-syntax-ns#List

http://burningbird.net/articles.htm


http://burningbird.net/dynatech.htm


http://burningbird.net/interact.htm

rdf:type

rdf:type

rdf:type

rdf:first

rdf:first

rdf:first

pstcn:menu

rdf:rest

rdf:rest

rdf:rest

12


Reification Reification

– A statement is modeled as a resource referenced by another statement

“Jonathon says those cherries are sweet.”

“Jonathon says…,” + “Those cherries are sweet.”

13

Jonathon

says

Those cherries sweetare

ReificationReified Statements (1/3)

The bases of reification in RDF– Model the original statement so that it can be referenced as

the subject of the newer statement

14

<rdf:Description rdf:about="http://www.webreference.com/dhtml/hiermenus/"> <pstcn:Contains>Tutorials and source code about creating hierarchical menus in DHTML</pstcn:Contains> </rdf:Description>

It is missing one thing: an assertion about who is making the recommendation

To. AliceI recommend you an useful link. http://www.webreference.com/dhtml/hiermenus is a source containing tutorials and source code about creating hierarchical menus in DHTML.……


An example

15

<?xml version="1.0"?> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:pstcn="http://burningbird.net/postcon/elements/1.0/" xml:base="http://burningbird.net/">

<rdf:Description rdf:about="#s1"> <rdf:subject rdf:resource="http://www.webreference.com/dhtml/hiermenus" /> <rdf:predicate rdf:resource="http://burningbird.net/schema/Contains" /> <rdf:object>Tutorials and source code about creating hierarchical menus in DHTML</rdf:object> <rdf:type rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement" /> </rdf:Description>

<rdf:Description rdf:about="http://burningbird.net/person/001"> <pstcn:recommends rdf:resource="#s1" /> </rdf:Description>

</rdf:RDF>


Subject: contains the identifier for the resource referenced within the statement Predicate: contains the property that forms the original context of the resource

(the property) Object: contains the value of the property that forms the original context of the

resource (the value) Type: contains the type of the resource

16

http://burningbird.net/

person/001 Tutorials and source code about creating hierarchical

menus in DHTML


#s1

http://www.webreference.com/dhtml/heirmenus

http://burningbird.net/schema/Contains


http://burningbird.net/postcon/elements/1.0/recommends

http://www.w3.org/1999/02/22-rdf-syntax-ns#subject

http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate

http://www.w3.org/1999/02/22-rdf-syntax-ns#object

http://www.w3.org/1999/02/22-rdf-syntax-ns#type

ReificationThe Necessity of Reification and Metastatements (1/2)

Why is reification necessary?– One could model the example in serialized RDF syntax and

not lose the information about who recommends the re-source

“Shelley Powers recommends…,” is not the actual web re-source

Web resource is actually an ancillary component of the rec-ommendation

17

<?xml version="1.0"?> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:pstcn="http://burningbird.net/postcon/elements/1.0/">

<rdf:Description rdf:about="http://www.webreference.com/dhtml/hiermenus/"> <pstcn:Contains>Tuturials and source code about creating hierarchichal menus in DHTML</pstcn:Contains> <pstcn:recommendedBy>Shelley Powers</pstcn:recommendedBy> </rdf:Description>

</rdf:RDF>

ReificationThe Necessity of Reification and Metastatements (2/2)

By being able to model the statement about the web resource– you can treat it as a property of another statement– You can be able to distinguish without confusion and without

ambiguity what “fact” you’re describing in an RDF statement

The importance of the distinction between the thing described and the object making the description is both the key and the confusion of reification

18

recommend

The thing described The object making the description

ReificationA Shorthand Reification Syntax (1/5)

A shorthand technique is particularly helpful in cir-cumstances other than just wanting a cleaner syntax

19


 <rdf:Description rdf:about="http://www.webreference.com/dhtml/hiermenus"> <pstcn:Contains rdf:ID='s1'> Tutorials and source code about creating hierarchical menus in DHTML</pstcn:Contains> </rdf:Description>

 <rdf:Description rdf:about="http://burningbird.net/person/001"> <pstcn:recommendedBy rdf:resource="#s1" /> </rdf:Description>

</rdf:RDF>


Recommend what – the web site or the author?

– Shelley Power recommends http://www.webreference.com/dhtml/ahiermenus, as a source of tutorials and source code for hierarchical menus cre-ated in DHTML

– Shelley Power recommends http://www.webreference.com/dhtml/ahiermenus, which is written by Peter Belesis

20

Shelley Power recommends http://www.webreference.com/dhtml/ahiermenus, written by Peter Belesis, as a source of tutorials and source code for hierarchical menus created in DHTML


21


<rdf:Description> <rdf:subject rdf:resource="http://www.webreference.com/dhtml/hiermenus" />

<rdf:predicate rdf:resource="http://burningbird.net/schema/Contains" /> <rdf:object>Tutorials and source code about creating hierarchical menus in DHTML</rdf:object>

<rdf:predicate rdf:resource="http://burningbird.net/schema/WrittenBy" /> <rdf:object>Peter Belesis</rdf:object> <rdf:type rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement" />

<pstcn:recommendedBy>Shelley Powers</pstcn:recommendedBy> </rdf:Description>

</rdf:RDF>

<rdf:Description rdf:about=“http://www.webreference.com/dhtml/hiermenus/”> <pstcn:Contains>Tutorials and source code about creating hierarchical menus in DHTML</pstcn:Contains> <pstcn:writtenBy>Peter Belesis</pstcn:writtenBy></rdf:Description>


An rdf:Bag acts as a container for all statements about a specific resource– rdf:bagID is used to identify the implicit Bag

22


<rdf:Description rdf:about="http://www.webreference.com/dhtml/hiermenus" rdf:bagID="R01"> <pstcn:contains> Tutorials and source code about creating hierarchical menus in DHTML</pstcn:contains> <pstcn:author>Peter Belesis</pstcn:author> </rdf:Description>

<rdf:Description rdf:about="http://burningbird.net/person/001"> <pstcn:recommendeds rdf:resource="#R01" /> </rdf:Description>

</rdf:RDF>


23


person/001Tutorials and source code about creating hierarchical menus in DHTML

http://unknown.org/

#R01

http://www.webreference.com/dhtml/heirmenus

http://burningbird.net/postcon/elements/1.0/contains

http://burningbird.net/postcon/elements/1.0/recommends





genid:ARP10834

http://www.w3.org/1999/02/22-rdf-syntzx-ns#Bag


http://www.burningbird.net/postcon/elements/1.0/

author

Peter Belesis

Peter Belesis

genid:ARP10833

http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement

Tutorials and source code about creating hierarchical menus in DHTML





http://burningbird.net/postcon/elements/1.0/contains

http://burningbird.net/postcon/elements/1.0/author

http://www.w3.org/1999/02/22-rdf-syntax-ns#_2

http://www.w3.org/1999/02/22-rdf-syntax-ns#_1

Documents

Practical RDF Chapter 4. Specialized RDF Relationships: Reification, Containers, and Collections