[om-list] N-ary relationships and simple sentences

[Thomas L. Packer at home]

Late response.

    I have been working on similar issues while trying to design my
interlingua -- but not quite similar enough for me to add much comment yet.

tomp

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----- Original Message ----- 
From: "Mark Butler" <butlerm at middle.net>
To: "One Model List" <om-list at onemodel.org>
Sent: Wednesday, 26 November, 2003 11:42
Subject: [om-list] N-ary relationships and simple sentences



After several weeks of effort and much struggle with binary
relationships in my meta model, I have concluded that tagged n-ary
relationships are much more practical, at least for my purposes.  That
is not to say that binary relationships are unusable, just that n-ary
relationships are more convenient.

I consider an event, like a collision to be a short temporal
relationship between multiple participants.  You can handle this in a
binary meta model by making the event a regular object and create binary
relationships between the event and the participants.  In my system all
relationships are first class objects, but all first class objects are
not formal relationships, so you have to decide a head of time.  In this
case the event was made into a plain vanilla object and the
participations were made into relationships.

But what if a relationship has other relationships?  For example if
friend(x,y) is a relationship between x and y, a third party z might
have an opinion about the quality of that relationship.  Indeed the very
fact the we have the word friendship indicates that we treat the
relationship as a first class object.  That is not a problem in and of
itself except for one thing - the roles x and y in a friendship are
preferred (and hard coded) so that if you are searching for the parties
to a relationship you have to look somewhere different (and in two
different places, subject (argument 1) and object (argument 2) than you
look to find other things that are related to the relationship.

My solution is to treat all first class relationships as generic
objects, like the event object I described above, and then use second
class relationships ("connections") to let an arbitrary number of
participants participate in any relationship, and furthermore to tag
those connections according to fundamental role in the relationship
(agent, subject, object, place, time, etc).

So in the friendship case, I have an object for x, and object for y, a
friendship object, and two connector objects, tagged as subject for the
connection to x, and object for the connection to y.  I can also add
other qualifiers as appropriate.

Now of course, one might object that I have merely pushed the problem
down a level - surely participation in an event needs to be treated as a
first class object.  It would be nice however, if connections did not
have to be first class objects with hard coded relationships, so my
solution is to treat connections like second class objects and create a
new first class object with a distinct pair of connections, if and only
if the lower level relationship implied by the connection needs to be
treated as a first class object.

This is rather similar to the way most natural languages work.  For
example if I say "A collided with B in 2002", the verb is the core
relationship object, A, and B are participants, '2002' is a related time
object, and the prepositions 'with' and 'in' are relationship
participation tags.  In languages like Latin and Korean, all parts of
the sentence would be tagged according to case (subject, object,
indirect object) etc.

But if I want to speak about A's responsibility for the collision, I
don't make a reference to the meta-relationship between A and the
collision per se, but rather speak of "A's responsibility for the
collision" - now responsibility is the key relationship with A and the
collision as tagged participants - 'A' is tagged as the owner, and
'collision' as the qualifier"

Comments?

 - Mark

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