Ontology I Cristian Cocos (CLIStFX)

Background: What? What is “Ontology”? What is an Ontology? Traditional answer: Theory of Everything Several other answers, more or less related: Theory of Existence Theory of “What There Is” (Description of Reality?)

Background: What? Taxonomizing Existence: categories of Existence The properties of Existence qua Existence (Properties of a rabbit seen as an existing thing, not as a (biological) organism) Analyzing Existence in its most general features: the most general attributes/properties of things, i.e. properties that every-thing has

Background: What? Quotes: Sowa: “The subject of ontology is the study of the categories of things that exist or may exist in some domain. The product of such a study, called an ontology, is a catalog of the types of things that are assumed to exist in a domain of interest D from the perspective of a person who uses a language L for the purpose of talking about D.”

Background: What? B. Smith: “Ontology as a branch of philosophy is the science of what is, of the kinds and structures of objects, properties, events, processes and relations in every area of reality. ‘Ontology’ is often used by philosophers as a synonym of ‘metaphysics’ (a label meaning literally: ‘what comes after the Physics’), a term used by early students of Aristotle to refer to what Aristotle himself called ‘first philosophy’. Sometimes ‘ontology’ is used in a broader sense, to refer to the study of what might exist; ‘metaphysics’ is then used for the study of which of the various alternative possible ontologies is in fact true of reality. (Ingarden 1964) The term ‘ontology’ (or ontologia) was coined in 1613, independently, by two philosophers, Rudolf Göckel (Goclenius), in his Lexicon philosophicum and Jacob Lorhard (Lorhardus), in his Theatrum philosophicum. Its first occurrence in English as recorded by the OED appears in Bailey’s dictionary of 1721, which defines ontology as ‘an Account of being in the Abstract’.

Background: What? B. Smith cont’d: “Ontology seeks to provide a definitive and exhaustive classification of entities in all spheres of being. The classification should be definitive in the sense that it can serve as an answer to such questions as: What classes of entities are needed for a complete description and explanation of all the goings-on in the universe? Or: What classes of entities are needed to give an account of what makes true all truths? It should be exhaustive in the sense that all types of entities should be included in the classification, including also the types of relations by which entities are tied together to form larger wholes.”

Background: Why? A related development (hardly noticed by philosophers): the term ‘ontology’ has gained currency in recent years in the field of computer and information science Why? One answer: theTower of Babel problem: Different groups of data- and knowledge-base system designers have their own idiosyncratic terms and concepts by means of which they build frameworks for information representation

Background: Why? Different databases may use identical labels but with different meanings Alternatively the same meaning may be expressed via different names How about sharing and translating? Problems standing in the way of putting this information together within a single system increase geometrically Methods must be found to resolve the terminological and conceptual incompatibilities which inevitably arise

Background: Why? Initially, such incompatibilities were resolved on a case-by-case basis Gradually it was recognized that the provision, once and for all, of a common reference ontology – a shared taxonomy of entities – might provide significant advantages over such case-by-case resolution

Background: Why? Hence the term ‘ontology’ came to be used by information scientists to describe the construction of a canonical description of this sort An ontology is in this context a dictionary of terms formulated in a canonical syntax and with commonly accepted definitions designed to yield a lexical or taxonomical framework for knowledge- representation which can be shared by different information systems communities

Background: Why? More ambitiously: an ontology is a formal theory within which not only definitions but also a supporting framework of axioms is included (perhaps the axioms themselves provide implicit definitions of the terms involved)

ULO (Potential) Advantages of ontology for the purposes of information management are/should be obvious: Each group of data analysts would need to perform the task of making its terms and concepts compatible with those of other such groups only once – by calibrating its results in the terms of the single canonical backbone language

ULO B. Smith: “If all databases were calibrated in terms of just one common ontology (a single consistent, stable and highly expressive set of category labels), then the prospect would arise of leveraging the thousands of person-years of effort that have been invested in creating separate database resources in such a way as to create, in more or less automatic fashion, a single integrated knowledge base of a scale hitherto unimagined, thus fulfilling an ancient philosophical dream of a Great Encyclopedia comprehending all knowledge within a single system.”

ULO There are obstacles standing in the way of the construction of a single shared ontology in the sense described Prodigious E.g.: the task of establishing a common ontology of world history would require a neutral and common framework for all descriptions of historical facts

ULO That, in turn would require that all legal and political systems, rights, beliefs, powers, and so forth, be comprehended within a single, perspicuous list of categories Not going to happen

ULO Other difficulties arise at the level of adoption: To be widely accepted an ontology must be neutral as between different data communities There is a (formidable) trade-off between the constraint of neutrality and the requirement that an ontology be maximally wide-ranging and expressively powerful – that it should contain canonical definitions for the largest possible number of terms

ULO Solution to these dificulties: ULO Upper Level Ontology = an ontology that would confine itself to the specification of such highly general (domain-independent) categories as: time, space, inherence, instantiation, identity, measure, quantity, functional dependence, process, event, attribute, boundary, and so on. (See, e.g., Aka formal ontology

ULO This top-level ontology would then be designed to serve as common neutral backbone, which would be supplemented by the work of ontologists working in more specialized domains on, for example, ontologies of geography, or medicine, or ecology, or law, or, still more specifically, ontologies of built environments (Bittner 2001), or of surgical deeds (Rossi Mori et al. 1997)

ULO A formal ontology/ULO comprises a representation of the categories of objects and of the relationships within and amongst categories that are to be found in any domain of reality whatsoever A material or domain ontology consists of a representation of the material categories and relationships amongst them that are to be found in some specific domain of reality

ULO …such as genetics, anatomy, plant-biology, cell-biology, physiology, etc. When one sets out to construct an ontology, it will most often be a material or domain specific ontology that one is interested in constructing However, for purposes of managing the sea of biomedical information, the relevance of formal ontology to the construction of material ontologies resides in …

ULO … its capacity to ensure interoperability or communication between and amongst domain ontologies Hence one of the primary reasons for interest in formal or “top-level” ontologies in the information science community is the promise that such ontologies hold out of making wide- spread interoperability possible

ULO Derived methodological observation: select a formal ontology to which to cling to Not many domain ontologies out there observe this rule That is why they are so messy

Competing Formal Ontologies John Sowa’s ontology (the “KR Ontology”):

Competing Formal Ontologies CIDOC-CRM Brainchild of Martin Dörr, an ACGT partnerMartin Dörr

Competing Formal Ontologies DOLCE: Descriptive Ontology for Linguistic and Cognitive Engineering ( cnr.it/DOLCE.html) cnr.it/DOLCE.html DOLCE devs. “do not intend DOLCE as a candidate for a “universal” standard ontology”

Competing Formal Ontologies SUMO: Suggested Upper Merged OntologySuggested Upper Merged Ontology created at Teknowledge CorporationTeknowledge Corporation Includes Sowa’s ontology(!)

Competing Formal Ontologies The crown jewel: BFOBFO recognizes a basic distinction between two kinds of entities: substantial entities or continuants, and processual entities or occurrents (“the great divide”) Corresponding to these are two basic and distinct perspectives that can be taken on the world, neither of which can fully represent the features of reality represented by the other:

Competing Formal Ontologies SPAN and SNAP The SNAP portion (or perspective) of BFO represents continuants: entities that endure through time while maintaining their identity BFO manual quote: “The SNAP ontology recognizes three major categories of continuants: dependent continuants, independent continuants and spatial regions. The defining feature of independent continuants is that they are the kinds of things in which other continuants, such as qualities and dispositions, can inhere. They are the bearers of qualities and other dependent continuants. The defining feature of dependent continuants is that they are the kinds of things (qualities, roles, functions) that inhere in or are born by something else (namely independent entities). Spatial regions are different from both independent and dependent continuants in that they neither inhere in anything, nor are they themselves bearers of qualities, thus nothing inheres in them. Each of these categories admits of further sub-divisions or sub-categories.”

Competing Formal Ontologies SPAN: “As opposed to SNAP, the SPAN portion or perspective of BFO represents occurrents: entities that happen, unfold, or develop in time. Examples of such entities include the process of respiration, a five mile run through the Black Forest, a whole human life in the 19th century, the development of an embryo, the functioning of a heart. The characteristic feature of occurrents, or processual entities, is that they are extended both in space (they occupy a definite spatial location at every time during which they exist), and also in time (understanding what a processual entity is, its identiy, requires knowing about how it has been at different times).”