Check: http://sig.biostr.washington.edu/projects/fm/FAQs.html (01)
Foundational Model of Anatomy (FMA) ontology
Modeling questions...
4) What does a merged hierarchy mean and why use one? (02)
Hope it is helpful. (03)
Marcia
________________________________________
From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
[mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Pat Hayes
Sent: Thursday, May 01, 2008 2:46 PM
To: Charles P. White
Cc: [ontolog-forum]
Subject: Re: [ontolog-forum] Heterarchy & Hierarchy, oh my my (04)
At 10:58 AM -0700 5/1/08, Charles P. White wrote:
Hello all, (05)
This is my first chime into the conversations so I hope my topic is
appropriate. (06)
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. (07)
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. (08)
Often referred to as 'multiple inheritance'. They are quite common in ontology
work. (09)
This
aspect is something that hurts my hierarchical mind. (010)
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." (011)
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. (012)
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? (013)
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. (014)
Pat (015)
Thanks for the bandwidth
Charles P. White (aka Jet Burns)
"This sentense has three erors." (016)
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