[RDF] Re: RDF digest, Vol 1 #36 - 2 msgs (fwd)

[Jonas Liljegren]

Dan Brickley <danbri@w3.org> writes:

> On 25 Sep 2000, Jonas Liljegren wrote:
> 
> > How do you represent anonymous resources?
> 
> Internally generated identifiers are necessary for database management,
> but if I don't know the 'real' URI for something I make sure I represent
> that lack of knowledge. Then I use meta-knowledge about certain predicates
> (eg. 'personalMailbox','corporateHomepage') to fold together nodes that
> 'must' be the same because they share a property/value pair that implies
> they are the self-same node...


 Statements
 ----------

Let's say you have two identical statements:

 S1: p1(s1,o1)
 S2: p1(s1,o1)

If these two statements belongs to the same model, we could merge S2
into S1. But if they belongs to diffrent models (maby stated at
diffrent times by diffrent agents) they are not the same stating
and can not have the same URI. (I remember the discussion about the
diffrence about the stating and the statement.)  We may look at S1 and
S2 (from diffrent models) as the same statement but diffrent statings.


 Subjects
 --------

Let's say we have:

 S1: p1(s1,o1)
 S2: p1(s2,o1)

This could be resolved by cardinality metadata. If p1 only allow one
subject for each object, you would have to resolve this in one way or
the other. Maby one of the statements are false.

If s1 and s2 are marked as autogenerated (and p1 has the said
constraint) s2 could be merged into s1. But it *could* be that S2 is a
false statement.  You would also have to consider the authority for
the two agents over the two subject namespaces.  Here is one
illustrating example:

 DB1: hasTheWorldRecordIn(Person1,Discus)
 DB2: hasTheWorldRecordIn(Person2,Discus)

(I would normaly switch place for subj and obj here, and the same
resoning holds for the same subj and diffrent objs, but we started the
example with diffrent subjs.)  What we see is that DB1 and DB2 has
diffrent ideas about who the record holder is.

If Person1 and Person2 has the same name and the same date of birth,
we could probably say that they are the same person.  But how much
verification do we need to say that s1 and s2 are the same?

I don't think that cardinality is enough for this.


 Literals
 --------

I have made a difference between static and dynamic literals; literals
that allways stays the same and literals that could change their
value.

 * A static literal resource represents the actual value.  This value
   can be the value of many properties.  These literals are actualy
   just normal resources that have a stored literal representation
   (and may have properties of its own).  A static literal can
   represent a specific web page.  It changes if the actual web page
   changes.

 * A dynamic literal represents the property for a specific resource.
   If the propery is the age of a specific resource, the literal would
   change continualy to represent the current age. But the literal URI
   would stay the same.

... You may know my view on literals:

http://jonas.liljegren.org/perl/proj/rdf/schema_editor/letters/literals_3.txt


This means that you can't merge literal URIs unless they are static
literals.  And how do you know if a literal is static or not?  Maby
another property for stating that?


-- 
/ Jonas  -  http://jonas.liljegren.org/myself/en/index.html