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First, any ontology formal language designed to formulate classes and their relationships has to include an ontology of relations describing their real features accompanied with the formal attributes.
This is not the case with the OWL created as adding better vocabulary than developed by XML, RDF, RDF Schema, DAML+OIL in formal description of classes, individuals and properties, like cardinality, equality, and other formal characteristics. The language is lacking many significant features of relations, both formal and real.Among real, first of all, the relation of cause and effect is fatally missing. Such defects come from the approach used, purely set-theoretical and formal logical, while any content-based (world) ontology distinguishes internal and external relations, avoiding their reduction to relational properties.'Being a parent' is merely a relational property, while 'parentage' (parenthood, but not the act or process of parenting) is a relation of parent to child. Or, more generally, the relational property of being a cause is just a monadic reduction of causality, the relation of cause to effect.
So, instead of classes and relational properties, we have rather to speak of classes and their relationships as two sorts of distinct entities. Besides, it will make a poor language to use the class/property distinction, where all properties are reduced to relational properties as a substitute of the relations of classes. In fact, there are several sorts of property, substantial (material, structural), stative (qualitative, quantitative), active (functional), along with relational (causal, spatial, temporal) properties, all such properties of a substantial class (genus) are to be the properties of its species and individuals. With such distinction, it makes a difference whether we just state that 'a class (a thing) have attributes (properties)' or that 'a thing has the properties to be a substance, to be in a state, to be acted or acting upon, and to be related to something else'. The later is a universal ontological statement, while the former is a general logical proposition. That is, from one side, to build a formal ontology language, one may develop a set-theoretic (logical) ontology constructed as a formal logical system composed of its objects-primitives, classes, individuals, and properties, logical syntax (notation techniques, formation and transformation rules), and formal semantics (model theory), as the OWL is doing.
From the other side, one can develop a true ontological system involving as its primitives Entity or Thing and the kinds of entities or things along with fundamental definitions, axioms and real-world semantics seeking the interpretation of the theory and its truth conditions in the world of things, entities, or beings.
Next demerit is tightly connected with the
first. Any general theoretical model or conceptual scheme or description
framework is built with some kinds of concepts,
individuals, predicates, attributes, or relations. If the model represents the
traits and features of the real world, its
predicates represent real properties. In so far as the scheme describes formal
objects, its predicates give description of formal properties, attributes,
or predicates. As a consequence, there are two
sorts of predicates: formal, logical attributes or real-valued, ontological
predicates. Failing to see such difference can
result in another conceptual mess and confusion. Proposing a general conceptual
scheme by using the class (object)/property (relation) distinction, the data type languages like OWL are missing the
meat of things. For such a formal data structure might not adequately
represent the whole gamut of the world entities
with their various interrelationships. We must clearly differentiate between
classes, properties, definitions as logical forms and entity types as ontological classes; for the definition and class and
property will always be in one of these thing types represented by the classes
of ontological predicates and signified by the
generic terms and expressions, such as thing, being or entity, substance or
object, state, property or quality and quantity, change or action or
process, and relation, like causality, time,
space. Any meaningful statements or propositions is always about one or another
of these types of entity, in two principal ways.
If the same type of predicate is asserted of its kinds (a quantity predicated of
magnitudes), it signifies its genus, a thing's essence. On the other side, if
one type of predicate is asserted of another
type, as equality and inequality relations are predicated of quantity,
sameness or difference relations, of substances, it signifies rather a property than an essence.
Thus, to construct a
high quality Web ontology language as a computational
ontology incorporating the basic rules of reasoning about the world
and its generic entities, we first need to formulate the universal
entity framework supporting all the major classes and relations in the single
hierarchy of things, as it is implicitly intended to achieve by the SUO project,
how successfully or unsuccessfully, this is another topic. And
designing such a (machine processible) ontology language system requires a
formal inquiry into the world's objects, states, changes, and relations as the
fundamental classes of ontological predicates specifying diverse kinds of entity
and realms of the world.
Azamat Abdoullaev
Director and Chief Scientist
EIS Encyclopedic Intelligent Systems LTD
Moscow, Russia
Pafos, Cyprus