Formal ontology
Encyclopedia
In philosophy, the term formal ontology is used to refer to an ontology
defined by axiom
s in a formal language
with the goal to provide an unbiased (domain
- and application-independent) view on reality, which can help the modeler of domain
- or application-specific ontologies (information science) to avoid possibly erroneous ontological assumptions encountered in modeling large-scale ontologies.
By maintaining an independent view on reality a formal (upper level) ontology gains the following properties:
Theories on how to conceptualize reality date back as far as Plato
and Aristotle
.
most formal upper level ontologies apply is that between endurants and perdurants.
Endurants are those entities
that can be observed-perceived as a complete concept, at no matter which given snapshot
of time
.
Were we to freeze time we would still be able to perceive/conceive the entire endurant.
Examples are material objects, such as an apple or a human, and abstract 'fiat' objects, such as an organisation or the border of a country.
Perdurants are those entities for which only a part exists if we look at them at any given snapshot in time.
When we freeze time we can only see a part of the perdurant. Perdurants are often what we know as processes, for example 'running'. If we freeze time then we only see a part of the running, without any previous knowledge one might not even be able to determine the actual process as being a process of running. Other examples include an activation, a kiss, or a procedure
.
or tropes.
Qualities do not exist on their own, but they need another entity
(in many formal ontologies this entity is restricted to be an endurant) in which they occupy. Examples of qualities and the values they assume are colors (red color), or temperatures (warm).
Most formal upper level ontologies recognize qualities, attributes, tropes, or something related, although the exact classification may differ. Some see qualities and the values they can assume (sometimes called quale) as a separate hierarchy
besides endurant & perdurant (example: DOLCE). Others classify qualities as a subsection of endurants, e.g. the dependent endurants (example: BFO
). Others consider property-instances or tropes that are single characteristics of individuals to be the atoms of the ontology, the simpler entities of which all other entities are composed, so that all the entities are sums or bundles of tropes (example: OCHRE
).
, otherwise it is informal.
In philosophy, a separate distinction between formal and nonformal ontologies exists, which does not relate to the use of a formal language
.
In a formal ontology, there is an optimal way to properly classify this concept, it is a kind of 'mobility', which is a kind of quality/property (see above). As a quality, it is said to inhere in independent endurant entities (see above), as such, it cannot exist without a bearer (in the case the arm).
It allows the modeller to focus on the content of the domain specific ontology without having to worry on the exact higher structure or abstract philosophical
framework that gives his ontology a rigid backbone. Disjoint axiom
s at the higher level will prevent many of the commonly made ontological mistakes made when creating the detailed layer of the ontology.
A formal ontology, on the other hand, represents entities without a particular application scope. Its hierarchy reflects ontological principles and a basic class-subclass relation between its concepts. A consistent framework like this is ideal for crossmapping data sources.
However, one cannot just integrate these external data sources in the formal ontology. A direct incorporation would lead to corruption of the framework and principles of the formal ontology.
A formal ontology is a great crossmapping hub only if a complete distinction between the content and structure of the external information sources and the formal ontology itself is maintained. This is possible by specifying a mapping relation between concepts from a chaotic external information source and a concept in the formal ontology that corresponds with the meaning of the former concept.
Where two or more external information sources map to one and the same formal ontology concept a crossmapping/translation is achieved, as you know that those concepts - no matter what their phrasing is - mean the same thing.
(NLP) and natural language understanding
(NLU) systems, ontology concepts are usually connected and symbolized by terms. This kind of connection represents a linguistic realization.
Terms
are words or a combination of words (multi-word units), in different languages, used to describe in natural language an element from reality, and hence connected to that formal ontology concept that frames this element in reality.
The lexicon
, the collection of terms and their inflections assigned to the concepts and relationships in an ontology, forms the ‘ontology interface to natural language’, the channel through which the ontology can be accessed from a natural language input.
or classifications, is that it allows for indefinite expansion. Given proper modeling, just about any kind of concept
ual information, no matter the content, can find its place.
Ontology
Ontology is the philosophical study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations...
defined by axiom
Axiom
In traditional logic, an axiom or postulate is a proposition that is not proven or demonstrated but considered either to be self-evident or to define and delimit the realm of analysis. In other words, an axiom is a logical statement that is assumed to be true...
s in a formal language
Formal language
A formal language is a set of words—that is, finite strings of letters, symbols, or tokens that are defined in the language. The set from which these letters are taken is the alphabet over which the language is defined. A formal language is often defined by means of a formal grammar...
with the goal to provide an unbiased (domain
Problem domain
A problem domain is the area of expertise or application that needs to be examined to solve a problem. A problem domain is simply looking at only the topics you are interested in, and excluding everything else. For example, if you were developing a system trying to measure good practice in...
- and application-independent) view on reality, which can help the modeler of domain
Problem domain
A problem domain is the area of expertise or application that needs to be examined to solve a problem. A problem domain is simply looking at only the topics you are interested in, and excluding everything else. For example, if you were developing a system trying to measure good practice in...
- or application-specific ontologies (information science) to avoid possibly erroneous ontological assumptions encountered in modeling large-scale ontologies.
By maintaining an independent view on reality a formal (upper level) ontology gains the following properties:
- indefinite expandability:
- the ontology remains consistent with increasing content.
- content and context independence:
- any kind of 'conceptConceptThe word concept is used in ordinary language as well as in almost all academic disciplines. Particularly in philosophy, psychology and cognitive sciences the term is much used and much discussed. WordNet defines concept: "conception, construct ". However, the meaning of the term concept is much...
' can find its place.
- any kind of 'concept
- accommodate different levels of granularityGranularityGranularity is the extent to which a system is broken down into small parts, either the system itself or its description or observation. It is the "extent to which a larger entity is subdivided...
.
Theories on how to conceptualize reality date back as far as Plato
Plato
Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...
and Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
.
Existing formal upper level ontologies (foundational ontologies)
- BFO - Basic Formal OntologyBasic Formal OntologyThe Basic Formal Ontology is a formal ontological framework developed by Barry Smith and his associates that consists in a series of sub-ontologies at different levels of granularity...
- DOLCE - Descriptive Ontology for Linguistic and Cognitive Engineering
- GFO - General Formal OntologyGeneral Formal OntologyThe general formal ontology is an upper ontology integrating processes and objects. GFO has been developed by Heinrich Herre, Barbara Heller and collaborators in Leipzig. Although GFO provides one taxonomic tree, different axiom systems may be chosen for its modules. In this sense, GFO provides...
- OCHRE - Object-Centered High-level REference ontologyObject-centered high-level reference ontologyThe Object-Centered High-level REference ontology is an upper ontology , a formal ontological framework whose purpose is to describe very general concepts that are the same across all knowledge domains....
- SUMO - Suggested Upper Merged OntologySuggested Upper Merged OntologyThe Suggested Upper Merged Ontology or SUMO is an upper ontology intended as a foundation ontology for a variety of computer information processing systems. It was originally developed by the Teknowledge Corporation and now is maintained by . It is one candidate for the "standard upper ontology"...
- UMBEL - Upper Mapping and Binding Exchange LayerUMBELUMBEL, short for Upper Mapping and Binding Exchange Layer, is an extracted subset of OpenCyc, providing the Cyc data in an RDF ontology based on SKOS and OWL 2...
Common terms in formal (upper-level) ontologies
The Difference in terminology used between separate formal upper level ontologies can be quite substantial, but the one and foremost dichotomyDichotomy
A dichotomy is any splitting of a whole into exactly two non-overlapping parts, meaning it is a procedure in which a whole is divided into two parts...
most formal upper level ontologies apply is that between endurants and perdurants.
Endurant
Also known as continuant, or in some cases 'substance'.Endurants are those entities
Entity
An entity is something that has a distinct, separate existence, although it need not be a material existence. In particular, abstractions and legal fictions are usually regarded as entities. In general, there is also no presumption that an entity is animate.An entity could be viewed as a set...
that can be observed-perceived as a complete concept, at no matter which given snapshot
Snapshot
Snapshot may refer to:* Snapshot , an amateur photograph* Snapshot, a 1979 Australian film directed by Simon Wincer* Snapshot, a novel by Garry Disher...
of time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....
.
Were we to freeze time we would still be able to perceive/conceive the entire endurant.
Examples are material objects, such as an apple or a human, and abstract 'fiat' objects, such as an organisation or the border of a country.
Perdurant
Also known as occurrent, accident or happening.Perdurants are those entities for which only a part exists if we look at them at any given snapshot in time.
When we freeze time we can only see a part of the perdurant. Perdurants are often what we know as processes, for example 'running'. If we freeze time then we only see a part of the running, without any previous knowledge one might not even be able to determine the actual process as being a process of running. Other examples include an activation, a kiss, or a procedure
Procedure (term)
A procedure is a sequence of actions or operations which have to be executed in the same manner in order to always obtain the same result under the same circumstances ....
.
Qualities
In a broad sense, qualities can also be known as propertiesProperty (philosophy)
In modern philosophy, logic, and mathematics a property is an attribute of an object; a red object is said to have the property of redness. The property may be considered a form of object in its own right, able to possess other properties. A property however differs from individual objects in that...
or tropes.
Qualities do not exist on their own, but they need another entity
Entity
An entity is something that has a distinct, separate existence, although it need not be a material existence. In particular, abstractions and legal fictions are usually regarded as entities. In general, there is also no presumption that an entity is animate.An entity could be viewed as a set...
(in many formal ontologies this entity is restricted to be an endurant) in which they occupy. Examples of qualities and the values they assume are colors (red color), or temperatures (warm).
Most formal upper level ontologies recognize qualities, attributes, tropes, or something related, although the exact classification may differ. Some see qualities and the values they can assume (sometimes called quale) as a separate hierarchy
Hierarchy
A hierarchy is an arrangement of items in which the items are represented as being "above," "below," or "at the same level as" one another...
besides endurant & perdurant (example: DOLCE). Others classify qualities as a subsection of endurants, e.g. the dependent endurants (example: BFO
Basic Formal Ontology
The Basic Formal Ontology is a formal ontological framework developed by Barry Smith and his associates that consists in a series of sub-ontologies at different levels of granularity...
). Others consider property-instances or tropes that are single characteristics of individuals to be the atoms of the ontology, the simpler entities of which all other entities are composed, so that all the entities are sums or bundles of tropes (example: OCHRE
Object-centered high-level reference ontology
The Object-Centered High-level REference ontology is an upper ontology , a formal ontological framework whose purpose is to describe very general concepts that are the same across all knowledge domains....
).
Formal versus nonformal
In information science an ontology is formal if it is specified in a formal languageFormal language
A formal language is a set of words—that is, finite strings of letters, symbols, or tokens that are defined in the language. The set from which these letters are taken is the alphabet over which the language is defined. A formal language is often defined by means of a formal grammar...
, otherwise it is informal.
In philosophy, a separate distinction between formal and nonformal ontologies exists, which does not relate to the use of a formal language
Formal language
A formal language is a set of words—that is, finite strings of letters, symbols, or tokens that are defined in the language. The set from which these letters are taken is the alphabet over which the language is defined. A formal language is often defined by means of a formal grammar...
.
Example
An ontology might contain a concept representing 'mobility of the arm'. In a nonformal ontology a concept like this can often be classified as for example a 'finding of the arm', right next to other concepts such as 'bruising of the arm'. This method of modeling might create problems with increasing amounts information, as there is no foolproof way to keep hierarchies like this, or their descendant hierarchies (one is a process, the other is a quality) from entangling or knotting.In a formal ontology, there is an optimal way to properly classify this concept, it is a kind of 'mobility', which is a kind of quality/property (see above). As a quality, it is said to inhere in independent endurant entities (see above), as such, it cannot exist without a bearer (in the case the arm).
Formal ontology as a template to create novel specific domain ontologies
Having a formal ontology at your disposal, especially when it consists of a Formal upper layer enriched with concrete domain-independent 'middle layer' concepts, can really aid the creation of a domain specific ontology.It allows the modeller to focus on the content of the domain specific ontology without having to worry on the exact higher structure or abstract philosophical
Philosophy
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...
framework that gives his ontology a rigid backbone. Disjoint axiom
Axiom
In traditional logic, an axiom or postulate is a proposition that is not proven or demonstrated but considered either to be self-evident or to define and delimit the realm of analysis. In other words, an axiom is a logical statement that is assumed to be true...
s at the higher level will prevent many of the commonly made ontological mistakes made when creating the detailed layer of the ontology.
Formal ontology as a crossmapping hub: crossmapping taxonomies, databases and nonformal ontologies
Aligning terminologies and ontologies is not an easy task. The divergence of the underlying meaning of word descriptions and terms within different information sources is a well known obstacle for direct approaches to data integration and mapping. One single description may have a completely different meaning in one data source when compared with another. This is because different databases/terminologies often have a different viewpoint on similar items. They are usually built with a specific application-perspective in mind and their hierarchical structure represents this.A formal ontology, on the other hand, represents entities without a particular application scope. Its hierarchy reflects ontological principles and a basic class-subclass relation between its concepts. A consistent framework like this is ideal for crossmapping data sources.
However, one cannot just integrate these external data sources in the formal ontology. A direct incorporation would lead to corruption of the framework and principles of the formal ontology.
A formal ontology is a great crossmapping hub only if a complete distinction between the content and structure of the external information sources and the formal ontology itself is maintained. This is possible by specifying a mapping relation between concepts from a chaotic external information source and a concept in the formal ontology that corresponds with the meaning of the former concept.
Where two or more external information sources map to one and the same formal ontology concept a crossmapping/translation is achieved, as you know that those concepts - no matter what their phrasing is - mean the same thing.
Formal ontology to empower natural language processing
In ontologies designed to serve natural language processingNatural language processing
Natural language processing is a field of computer science and linguistics concerned with the interactions between computers and human languages; it began as a branch of artificial intelligence....
(NLP) and natural language understanding
Natural language understanding
Natural language understanding is a subtopic of natural language processing in artificial intelligence that deals with machine reading comprehension....
(NLU) systems, ontology concepts are usually connected and symbolized by terms. This kind of connection represents a linguistic realization.
Terms
Terminology
Terminology is the study of terms and their use. Terms are words and compound words that in specific contexts are given specific meanings, meanings that may deviate from the meaning the same words have in other contexts and in everyday language. The discipline Terminology studies among other...
are words or a combination of words (multi-word units), in different languages, used to describe in natural language an element from reality, and hence connected to that formal ontology concept that frames this element in reality.
The lexicon
Lexicon
In linguistics, the lexicon of a language is its vocabulary, including its words and expressions. A lexicon is also a synonym of the word thesaurus. More formally, it is a language's inventory of lexemes. Coined in English 1603, the word "lexicon" derives from the Greek "λεξικόν" , neut...
, the collection of terms and their inflections assigned to the concepts and relationships in an ontology, forms the ‘ontology interface to natural language’, the channel through which the ontology can be accessed from a natural language input.
Formal ontology to normalize database/instance data
The great thing about a formal ontology, in contrast to rigid taxonomiesTaxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
or classifications, is that it allows for indefinite expansion. Given proper modeling, just about any kind of concept
Concept
The word concept is used in ordinary language as well as in almost all academic disciplines. Particularly in philosophy, psychology and cognitive sciences the term is much used and much discussed. WordNet defines concept: "conception, construct ". However, the meaning of the term concept is much...
ual information, no matter the content, can find its place.