Dear John, (01)
See below. (02)
> JFS
> >> HDQM
> >> kind_of_activity
> >> A class_of_activity all of whose members are of the same kind.
> >>
> >> Much simpler:
> >> kind_of_activity: a one-place relation that is true of every
> >> activity of the same kind.
>
> MW
> > I disagree. Class_of_activity is the supertype of kind_of_activity,
> > and you leave no place for it. For end users, class is much easier to
> > relate to than one place relations, which is a logic view point. I
> > would not with to burden users with that. I might not choose class if
> > I had my time again, but in ISO 15926 that is history now, and
> > changing it would be more confusing than leaving it the same.
>
> There are four separate issues in that comment:
>
> 1. What is the simplest metalanguage for talking about ontology and
> its mapping to logic?
>
> 2. How do you define and explain types and subtypes in ways that are
> logically sound and pedagogically effective for most people.
>
> 3. How do we design a good user interface and explain it to domain
> experts who have never studied logic or ontology?
>
> 4. How are these issues related to specific ISO standards?
>
> I answered question #1 in my previous note. The short summary is that
> all the mainstream logic notations are based on four kinds of primitive
> notions: relations (or predicates), quantifiers, variables (or names
> or some graphic equivalent), and Boolean operators. Everything else
> can be defined in terms of these four. (03)
MW: If I were wishing to reason over the "ontology" I would probably use an
ontology language that used those primitives. But that is not the purpose of
the ontologies I have been developing. The primary purpose has been the
definition of data structures to hold instance of the ontology, or the
record structures for the exchange of data. Any reasoning would be over the
data instances rather than the ontology itself. (04)
MW: There are some interesting requirements that arise from this. You can
only hold data when you have defined appropriate structures, so much of the
ontology is permissive, defining the sorts of things that can be said. This
is not generally the case with logic based ontologies, that are
unstructured, and when you want to say something you just say it, and you
are generally not so concerned with instances of the ontology (though you
can be of course, but it is likely to be rather inefficient if there are
large volumes of instances).
The result of this is that much of the ontology is permissive, setting out
the kinds of things that can be said. Logic is not particularly good for
this, but an entity relationship language such as EXPRESS is. It has the
things that you describe. So for example, in the definition you took an
excerpt from: (05)
ENTITY class_of_spatio_temporal_extent
SUBTYPE OF (class);
member_of_ : OPTIONAL SET [1:?] OF
class_of_class_of_spatio_temporal_extent;
END ENTITY; (06)
The first line says that class_of_spatio_temporal_extent is an ENTITY (this
is equivalent to saying that class_of_spatio_temporal_extent is a unary
predicate) (07)
The second line says that class_of_spatio_temporal_extent is a subtype of
class. (08)
The third line (a bit turtle like) declares a binary predicate where the
places are filled by a member of class_of_spatio_temporal_extent and
class_of_class_of_spatio_temporal_extent. (09)
You have of course picked just about the most obscure bit of the data model,
but instances of class_of_spatio_temporal_extent are the subtypes of
spatio_temporal_extent, and instances of
class_of_class_of_spatio_temporal_extent are subtypes of
class_of_spatio_temporal_extent. These are structures you need to give
yourself flexibility and extensibility at lower levels. If you don't make
these declarations, you can't hold those things.
>
> Aristotle answered question #2 in a form that is widely used today:
> assign a noun phrase to each category (monadic relation) in ontology.
> In the 3rd century AD, Porphyry organized the categories in a tree and
> introduced the drawing conventions we still use today. (010)
MW: That is pretty much what we do, and EXPRESS-G gives you a reasonable
graphical form for the tree (there is multiple inheritance of course).
>
> For question #3, my recommendation is to develop tools that use the
> same terminology and diagrams that the domain experts use. That means
> that we need tools that can support controlled NLs and widely used
> graphics.
> The tools should support methods for tailoring the graphics by adapting
> symbols, shapes, and styles to the conventions of any special domain. (011)
MW: There is a big gap between what domain experts do and what is necessary
for ontology. Generally ontology requires greater precision than is usually
provided by domain experts without specific training. The alternative is to
have an intermediary who does the analysis to fill the gap between the
domain experts and the precision needs of an ontology.
>
> For question #4, we cannot change any official standard. But we can
> recommend mappings of the standards to and from the notations above. (012)
MW: Indeed. The EXPRESS version of ISO 15926 has already been mapped to OWL
full. Generally, you cannot perform an automated mapping, you rather have to
do a restatement in terms of the new language, taking account of its
particular limitations and capabilities. (013)
Regards (014)
Matthew West
Information Junction
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