[Person-ontology] Binary or Ternary? (was D7 - Which languages are better than OWL?)

[James Nerney]

Merely as a convenience, I revise the disputed sentence to read,  
"Mary hands the book over to Tom."  This sentence describes a process  
involving three entities: Mary, Book, and Tom.
The process has a beginning and an end and it has inputs and outputs.
	Input state:   Mary is holding Book.  Tom is not holding Book.
	Output state:  Mary is not holding Book.  Tom is holding Book.
For this process there is an intermediate state: Mary and Tom are  
holding Book.  A name for the process can be Hands-Over.

The states in this process can be described as relationships.
For the Input state:
	Mary is related to Book by Holds relationship.
	Tom is related to Book by NotHolds relationship.
For the Output state:
	Mary is related to Book by NotHolds relationship.
	Tom is related to Book by Holds relationship.
For the Intermediate state:
	Mary is related to Book by Holds relationship.
	Tom is related to Book by Holds relationship.

The process includes a complex of relationships.  The pair Mary and  
Book can be viewed as having a dynamic relationship, that is, the  
relationship between the two entities changes in nature from the  
beginning of the process to the end of the process.  A change in  
relationship can be described by identifying the initial  
relationship, the final relationship, and by describing the change as  
a constraint between the initial relationship and the final  
relationship.  In this case, the constraint is sequential. A name for  
this constraint can be Becomes; in other words, Holds Becomes  
NotHolds.  Also, the pair Tom and Book can be viewed as having a  
dynamic relationship, and can be treated in the same way as the  
dynamic relationship between Mary and Book.  Still another constraint  
is that both "Mary Holds Book" and "John Holds Book" relationships  
occur at some instant.  A name for this constraint may be Co-occurs.   
The relationships within the Hands-Over process can be completely  
identified by the use of Holds relationship, NotHolds relationship,  
Becomes constraint, and Co-occurs constraint.  This complex of  
relations within the Hands-Over process can be named the Hands-Over  
relationship.

What is the arity of the Hands-Over relationship? Answering that  
question requires abstracting a static relationship to represent the  
entire Hands-Over relationship.  The complex of relationships that  
happen in the intermediate state seems a good stand-in for the entire  
Hands-Over relationship.  That complex includes the "Mary Holds Book"  
and "John Holds Book" relationships and the Co-occurs constraint.   
Removing time from the complex leaves Mary, Book, and Tom.  Two  
different descriptions of this timeless relationship are possible:  
(1) a binary relationship where Tom and Mary are Entities and Book  
relates Tom and Mary to each other in a physical way, and (2) a  
ternary relationship where all three are entities which take  
participant roles in the Hands-Over relationship.  As John points  
out, purpose is relevant.  Which kind of relationship  to choose,  
binary or ternary, depends on the purpose of the model.

The above analysis does not depend on how the word situation is  
defined nor does it depend on the number of qualifiers that may be  
added to the sentence.


JS> ... Two points:  First, linguists who talk about case roles  
distinguish obligatory roles from optional roles.  Second, the word  
"situation" is notoriously difficult to define.  In 1983, Barwise &  
Perry tried to make situations the foundation for their theory of  
semantics.  For a few years, there was a strong current of activity  
dedicated to that approach.  But it came to grief over one serious  
problem: Nobody was ever able to define the central term 'situation'...

PH> What do you mean by a n-ary *situation* ? The situation being  
described has no intrinsic 'arity' (a point made many years ago by, I  
believe, Strawson), because one can go on adding qualifiers endlessly  
(he did it... at midnight... in the kitchen... last week... with a  
knife... silently... rapidly...). In fact, this has been used as an  
argument (to me, convincing) for the naturalness of the binary case- 
based representation over the use of n-ary relations.

GPZ> ... a dynamic situation like that represented by "Mary has given  
a book to Bill", you must introduce a predicate in the form of GIVE,  
MOVE or whatever, and take into account the fact that "Mary",  
"book-1" and Bill" - apart from being instances of ordinary concepts  
in a standard ontology - are also characterized by given logical  
relationships with this predicate.

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