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Contents 1 Describing Ownership 1.1 Discussion 1.2 Alternative example 1.3 Issues 1.4 References

[edit] Describing Ownership

Question: How might we describe that we own something? E.g. a book, an album, a car, dog, etc.

[edit] Discussion

The simplest way of stating that "I own a copy of the book 1984", might be something like this:

<foaf:Person>
  <ns:owns>
    <book:Book dc:title="1984"/>
  </ns:owns>
</foaf:Person>

This is nice and straight-forward because the "owns" property is quite general and we could use it to capture a wide variety of types of "ownership" (e.g. leasing, etc). It's therefore similar to

foaf:knows

: a simple, but useful relationship between a person and some Thing.

But using a simple property is limited. There are a number of other useful aspects to an ownership relationship that I might want to capture, e.g. how did I acquire something? was it a gift, an inheritance, did I buy it, or did I find it in the street?; and when did the ownership begin (and when might it end)?; if I bought it, then from where or from whom?

Therefore a more useful way to model ownership would be as a class, which we can then annotate with additional properties, e.g:

<ns:OwnedItem>
  <ns:owner>
    <foaf:Person/>
  </ns:owner>
  <ns:item>
    <book:Book dc:title="1984"/>
  </ns:item>
  <dc:date>2003-12-25</dc:date>
  <ns:source>
    <foaf:Person/>
  </ns:source>
</ns:OwnedItem>

In that example we're stating that one person owns a copy of a book called 1984, which they acquired on 25th December 2003, from another person.

The

OwnedItem

class could be extended to model additional types for specific kinds of ownership, e.g.

Gift

,

Inheritance

,

FoundItem

,

Purchase

.

Gift

may itself be sub-classed to describe particular types of gift, e.g. Xmas present, birthday present, leaving present, etc.

Here's a more detailed example that demonstrates this:

<foaf:Person rdf:nodeID="ldodds">
  <foaf:name>Leigh Dodds</foaf:name>
  <book:reading rdf:nodeId="bk"/>
</foaf:Person>
<ns:OwnedItem>
  <ns:owner rdf:nodeID="ldodds"/>
  <ns:source>
     <foaf:Person rdf:nodeID="debs"/>
  </ns:source>
  <dc:date>2003-12-25</dc:date>
  <ns:item rdf:nodeId="bk"/>  
  <rdf:type rdf:resource=".../Gift"/>
</ns:OwnedItem>
<book:Book rdf:nodeID="bk">
  <dc:title>1984</dc:title>
  <foaf:maker>
    <foaf:Person>
      <foaf:name>George Orwell</foaf:name>
    </foaf:Person>
  </foaf:maker>
</book:Book>

[edit] Alternative example

By coining an inverse of ns:owner, e.g. ns:hasOwnership, and renaming OwnedItem (which seems to suggest that e.g. Book is a subclass) to Ownership, the above can be shown a little clearer and perhaps more intuitive:

<foaf:Person>
  <foaf:name>Morten Frederiksen</foaf:name>
  <book:reading rdf:nodeId="bk"/>
  <ns:hasOwnership>
    <ns:Ownership>
      <ns:source>
        <foaf:Person foaf:nick="jen"/>
      </ns:source>
      <dc:date>1993-07-12</dc:date>
      <ns:item rdf:nodeId="bk"/>  
      <rdf:type rdf:resource=".../Gift"/>
    </ns:Ownership>
  </ns:hasOwnership>
</foaf:Person>
<book:Book rdf:nodeID="bk">
  <dc:title>The Bourne Identity</dc:title>
  <foaf:maker>
    <foaf:Person>
      <foaf:name>Robert Ludlum</foaf:name>
    </foaf:Person>
  </foaf:maker>
</book:Book>

Note that above doesn't change anything modelling wise - it's still a non-binary relation.

With a suitable range for hasOwnerShip, the RDF/XML could be even cleaner. Of course, it could even be renamed to foaf:owns...

[edit] Issues

* the usual work vs. manifestation of a work issue: I don't "own" 1984, I own a copy of the book with that title. Is this something we need to worry about?
 I think we do, as otherwise we'd get confused with e.g. music - the maker can make reasonable copyright statements about a CD as a work, whereas I can make reasonable statements about ownership of the copy i bought. -- MortenFrederiksen

[edit] References

* A scheme already somewhat defining ownership: The Charette Relationship Set (CRS)
* Proposal for foaf:owns property
* Discussion on #foaf where mortenf suggests Ownership should be a class
* More irc chat bryce on short term owning, e.g. renting a vid
* Wordnet definition of ownership