Re: [ontolog-forum] Heterarchy & Hierarchy, oh my my

[Pat Hayes <phayes@xxxxxxx>]

At 10:58 AM -0700 5/1/08, Charles P. White wrote:

> Hello all,
>
> This is my first chime into the conversations so I hope my topic
> is
> appropriate.
>
> At present, I'm working as the lead of NASA/JPL's Spacecraft
> Problem
> Reporting System (PRS), which is a web based application where an
> engineer or scientist can report a problem with a spacecraft that
> is
> in-flight, or under development.  When an "anomaly" is
> created, it is
> then  automatically dispatched to the proper team of folks that
> can
> triage and solve the problem, sign, and close the issue.
>
> Presently, we are using a hierarchy to define the structure of the
> individual items that make up the spacecraft.  It is a
> typical
> parent-child-grandchild relationship.  However, I am running into
> a
> cases where a child can have more then one non-related
> parents.

Often referred to as 'multiple inheritance'. They are quite common in ontology work.

>  This
> aspect is something that hurts my hierarchical mind.
>
> I have recently found the concept of heterarchy in my knowledge
> management quests and find it maybe the answer.  From Wikipedia,
> "In
> a group of related items, heterarchy is a state wherein any pair
> of
> items is likely to be related in two or more differing ways.
> Whereas
> hierarchies sort groups into progressively smaller categories and
> subcategories, heterarchies divide and unite groups variously,
> according to multiple concerns that emerge or recede from
> view
> according to
> perspective."

That sounds like a rather general and permissive kind of definition. Do you really need to go that far? Would it be enough to have something like a hierarchy - a tree - but to allow branches to merge downwards, so that a given entry might be on more than one path from the root? A directed acyclic graph (DAG) rather than a tree? Notice this still has the property that going downwards on any given branch gives you progressively smaller categories, and it rules out 'loops' of inheritance.

> My challenge/question is, how would define and represent the
> heterarchy in a designator system?  We all know how to
> express
> hierarchy as 1.3.54.A for example, but when an item has more then
> one
> parent, how can we express that in an equally simplistic
> way?

You can't, other than by obvious tricks such as having a collection of such designators for each item. But why do you need to? You can maintain the structure in other ways. For example, an RDF triple store can represent an arbitrary DAG structure, and all that is required is that each entry have a unique name of some kind.

Pat

> Thanks for the bandwidth
> Charles P. White (aka Jet Burns)
> "This sentense has three erors."
>
>
>
>  
> _________________________________________________________________
> Message Archives:
> http://ontolog.cim3.net/forum/ontolog-forum/ 
> Subscribe/Config:
> http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/ 
> Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
> Shared Files: http://ontolog.cim3.net/file/
> Community Wiki: http://ontolog.cim3.net/wiki/
> To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx
>

-- 

---------------------------------------------------------------------
IHMC               (850)434 8903 or (650)494 3973   home
40 South Alcaniz St.       (850)202 4416   office
Pensacola                 (850)202 4440   fax
FL 32502                     (850)291 0667    cell
http://www.ihmc.us/users/phayes      phayesAT-SIGNihmc.us
http://www.flickr.com/pathayes/collections

_________________________________________________________________
Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/  
Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/  
Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
Shared Files: http://ontolog.cim3.net/file/
Community Wiki: http://ontolog.cim3.net/wiki/ 
To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx    (01)