Information technology Ontologies Top-Level Ontologies (TLO) Part 1: Requirements

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1 ISO 2017 All rights reserved Reference number of working document: ISO/IEC JTC1 SC32 WG2 Nxxxx Date: Reference number of document: ISO/IEC WD Committee identification: ISO/IEC JTC1 SC32 WG2 SC32 Secretariat: US Information technology Ontologies Top-Level Ontologies (TLO) Part 1: Requirements Warning This document is not an ISO International Standard. It is distributed for review and comment. It is subject to change without notice and may not be referred to as an International Standard. Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to provide supporting documentation. Document type: International standard Document subtype: if applicable Document stage: (10) Working draft Document language: E

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3 WORKING DRAFT ISO/IEC WD Copyright notice This ISO document is a working draft or committee draft and is copyright-protected by ISO. While the reproduction of working drafts or committee drafts in any form for use by participants in the ISO standards development process is permitted without prior permission from ISO, neither this document nor any extract from it may be reproduced, stored or transmitted in any form for any other purpose without prior written permission from ISO. Requests for permission to reproduce this document for the purpose of selling it should be addressed as shown below or to ISO s member body in the country of the requester: ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel Fax copyright@iso.org Web Reproduction for sales purposes may be subject to royalty payments or a licensing agreement. Violators may be prosecuted. ISO 2017 All rights reserved 1

4 Contents Page Introduction Scope Normative references Terms and definitions Conformance Requirements for conformance Informative Annex: Examples of ontology suites ISO 2017 All rights reserved

5 Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 2017 All rights reserved 3

6 Introduction This standard was developed in response to worldwide demand for ontology-based solutions to the problem of semantic interoperability across networks of information systems. The demand arises particularly from large organizations and consortia of organizations in areas such as bioinformatics, healthcare, the manufacturing industry, and military and government administration, where independently created information systems need to exchange data in such a way that meaning is preserved. At its core, an ontology is a collection of terms organized into a graph hierarchy. An ontology can help to achieve sharing of meaning because terms in the hierarchy are associated with formal definitions specifying their meanings in a way that can be processed computationally. If an ontology can be shared across participating organizations, then data can be exchanged in such a way that meaning is preserved if the data can be associated with corresponding shared ontology terms. Where heterogeneous bodies of data need to be exchanged or manipulated, some have adopted approaches that involve a distinction of levels, with a single very general ontology at the top governing one or more specific ontologies at lower levels. This international standard addresses the need for those communities that have adopted such multi-level approaches. The purpose of the standard is to specify the requirements that a top-level ontology shall satisfy if it is to serve the needs of those building or re-engineering ontologies or other legacy systems at lower levels in a way that will support semantic interoperability among them. To be assured a Top-Level Ontology is fit for purpose, it needs to have appropriate content that is well documented and be available in computer interpretable forms suitable for reasoning. The detail of this standard specifies requirements that a Top Level Ontology shall meet in terms of coverage, documentation and representation. 4 ISO 2017 All rights reserved

7 Information technology Information technology Ontologies Top-Level Ontologies (TLO) Part 1: Requirements 1 Scope Part 1 of this International Standard specifies required characteristics of a domain neutral top-level ontology (TLO) that can be used in tandem with domain ontologies at lower levels to support data exchange, retrieval, discovery, integration and analysis. The primary focus of the standard is the design and use of suites of purpose-built ontologies. However, the standard can serve also other goals related to the achievement of semantic interoperability, for example as concerns legacy ontologies developed using heterogeneous upperlevel categories, where a coherently designed top-level ontology can provide a target for re-engineering. The primary purpose of a top-level ontology as defined by this standard is to promote consistency and nonredundancy among a plurality of domain-specific ontologies by providing a common starting point for definitions. This International Standard specifies the characteristics that an ontology shall possess if it is to serve this purpose in support of the goals of data exchange, retrieval, integration and analysis by computer systems. An ontology is on the one hand an artifact for human use, built out of terms and relations expressed using natural language. On the other hand it is an artifact for use by computers, so that these terms and relations need to be captured in a formal language. Multiple languages have been developed for the purposes of ontology formalization, of which Common Logic (CL) (ISO/IEC 24707:2007) [1] and the Web Ontology Language (OWL) specifically OWL 2 DL, as specified in [2] are normative for this standard. These languages serve different ends. CL is a logical framework with the full expressivity of first-order logic (FOL), the unifying framework of semantic web applications. This expressivity is needed if a TLO is to meet the requirements of this standard, since weaker expressivity would not allow the ontology to capture in a formal way the implications of axioms in areas such as mereology and the theory of location. OWL 2 DL is a more weakly expressive language that has the advantage of being a decidable subset of FOL.This means that it can be used by both humans and computer systems to support not only exchange of information with preservation of meaning but also logical deductions from this information. This International Standard focuses on TLOs as they are used in modular ontology architectures as resources designed to support the interchange of information among heterogeneous information systems. The following are within the scope of this International Standard: Specification of the requirements an ontology shall satisfy if it is to serve as a top-level hub ontology in such an architecture. Specification of the relations between a top-level ontology and domain ontologies in such an architecture. Specification of the role played by the terms in a top-level ontology in the formulation of definitions and axioms in ontologies at lower levels. The following are outside the scope of this International Standard: Specification of ontology languages, including the languages RDF, OWL, and Common Logic used in ontology development with a standard model-theoretic semantics. Specification of methods for reasoning with ontologies. ISO 2017 All rights reserved 5

8 Specification of translators between the notations of ontologies developed in different ontology languages. Specification of rules governing the use of IRIs as permanent identifiers for ontology terms. Specification of the principles of ontology maintenance and versioning. Specification of how ontologies can be used in the tagging or annotation of data. 6 ISO 2017 All rights reserved

9 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO/IEC 24707, Information technology Common Logic (CL): a framework for a family of logic-based languages ISO/IEC :2010 Information technology Metamodel framework for interoperability (MFI) Part 3: Metamodel for ontology registration W3C Recommendation OWL 2 Web Ontology Language Document Overview W3C Recommendation OWL 2 Web Ontology Language Structural Specification and Functional-Style Syntax W3C Recommendation Linked Data Platform 1.0 ISO 2017 All rights reserved 7

10 3 Terms and definitions The following definitions are introduced for the purposes of this and subsequent parts of this document. 3.1 entity any concrete or abstract thing of interest SOURCE: ISO :2003, 3.7 NOTE 1: Entity is employed in many ontology communities as an all-inclusive term including everything whatsoever, whether or not it is perceivable or measurable, thus including physical things, attributes, qualities, roles, powers, institutions, languages, theories, types, classes, events, information systems, and so forth. Various alternative terms have played the role of all-inclusive term in contemporary ontology, including class, concept, individual, term, type and item. Thing is used in OWL to refer to the class of all individuals; entity to refer to the union of: classes, datatypes, object properties, data properties, annotation properties, and named individuals [Error! Reference source not found.]. 3.2 class a general entity with particulars as members or instances SYNONYM: type NOTE: Classes or types are referred to by general expressions EXAMPLES: Examples of general expressions in natural language are common nouns and noun phrases such as: electron, explosion, phosphorylation, nuclear reactor ; actual world, spatial region, temporal quality, Examples of such expressions in technical languages include model numbers, disease codes, aircraft type designators. 3.3 particular an individual entity SYNONYM: individual NOTE 1: Particulars are referred to by particular referring expressions. In contrast to classes or types, particulars are not exemplified or instantiated by further entities. NOTE 2: In some ontologies instance is used as a synonym for particular. EXAMPLES: Examples of general expressions in natural language are proper names such as Donald J. Trump. Examples of such expressions in technical languages include serial numbers, social security numbers, dates. latitudes and longitudes. 3.4 relation the way in which two or more entities are connected NOTE 1: Relations can hold between individuals or between classes or types; they can also hold between individuals and classes or types. NOTE 2: Relation here is a generalization of what in OWL is called an object property. In OWL object properties are restricted to relations between pairs of individuals. EXAMPLES: Examples of relational expressions are: is a (also known as subtype or subclass ), part of, member of, instantiates, member later than, temperature of, temperature of at time. Such expressions form complete sentences when used in conjunction for example with common nouns and noun phrases. 3.5 term 8 ISO 2017 All rights reserved

11 an expression that refers to some class or to some individual SYNONYM: denotes is a synonym of 'refers to' NOTE 1: An ontology will typically contain a unique preferred term for the entities within its coverage domain, NOTE 2: OWL uses the term label to comprehend both preferred terms for classes and preferred relational expressions for object properties. 3.6 definition a concise statement of the meaning of a term or relational expression SOURCE: adapted from ISO 15225:2016, 3.5 NOTE: For the purposes of this standard definitions satisfying 3.2 can be of two sorts: (i) those formulated using a natural language such as English, supplemented where necessary by technical terms or codes used in some specialist domain; (ii) those formulated using a computer-interpretable language such as OWL or CL. 3.7 axiom a statement that is taken to be true, to serve as a premise for further reasoning SOURCE: ISO/TS :2012 NOTE 1: In a computational setting, an axiom is a sentence that is never posed as a goal to be proved, but only used to prove other sentences. NOTE 2: Axioms may be formulated as natural language sentences or as formulae in a computer interpretable language. 3.8 ontology a collection of terms and relational expressions, together with definitions and axioms expressed in a computer interpretable language NOTE 1: In many ontology communities the terms in an ontology consist exclusively of common nouns and noun phrases representing classes or types. Some ontologies allow also terms representing certain privileged specific instances ( distinguished individuals ). EXAMPLES: Examples of distinguished individuals include: the actual world, spacetime, the universe. In an ontology of US law such examples might include: the US Supreme Court. NOTE 2: An ontology that is combined with large bodies of data about individuals is referred to as a knowledge base (see definition 3.9) NOTE 3: The term ontology is sometimes used in a narrow sense to refer to specific formal representations. In this standard, however, an ontology is conceived as an artefact created by humans in time, comparable in this respect to a scientific theory or to a lexicon. Thus an ontology may exist in different versions at different times, for example as a result of the fact that errors are corrected or new terms added. NOTE 4: In logical contexts the word signature is used to represent the set of non-logical symbols of a formal language or formal theory. The signature of an ontology consists of two sorts of non-logical symbols: terms and relational expressions. NOTE 5: Computer interpretable representation here signifies representation in a formal-logical language, such as OWL or CL, developed for ontology purposes. Many ontologies are formalized in multiple such languages. If more than one formalization is provided which are not logically equivalent, then these should form a set linearly ordered in terms of theory strength, where theory A is stronger than theory B when B is interpretable in A, but A is not interpretable in B. Theory B is ISO 2017 All rights reserved 9

12 interpretable in theory A iff (if and only if) the language of B can be translated into the language of A so that every theorem of B is derivable in A. An ontology developed in OWL 2 DL is always interpretable in CL, but not vice versa. NOTE 6: From the definitions and axioms in the ontology it should be possible to infer a series of is-a (subtype or subclass) statements of the form A is-a B, as well as statements asserting other sorts of relations between the terms in the ontology, for example mereological assertions (that A is part of B) or temporal assertions (that A occurs later than B), and so on. NOTE 7: In both OWL and CL, definitions are treated as axioms asserting equivalence. NOTE 8: In the literature on OWL 1 an ontology is defined as: a collection of information, generally including information about classes and properties [4]. In the literature on OWL 2 an ontology is defined as: a formal description of a domain of interest [5]. The definition provided here is intended to be compatible with both of these definitions. NOTE 9: Existing ISO definitions of ontology are: a) formal representation of phenomena of a universe of discourse with an underlying vocabulary including definitions and axioms that make the intended meaning explicit and describe phenomena and their interrelationships (from ISO :2014 [9]; reused in ISO :2015, and in ISO 19154:2014, 4.16). b) specification of concrete or abstract things, and the relationships among them, in a prescribed domain of knowledge. ISO/IEC :2010, [7] c) a logical structure of the terms used to describe a domain of knowledge, including both the definitions of the applicable terms and their relationships. ISO/IEC/IEEE 24765:2010, (from IEEE Std (R2007) IEEE Guide for CASE Tool Interconnections-Classification and Description.3.9) d) organization of concepts for which a rational argument can be made. ISO/TR 13054:2012, 2.6 e) explicit and consensual specification of concepts of an application domain independent of any use of these concepts. ISO :2015, 3.1 f) rigorous conceptual schema representing the subject domain. ISO/TR 25100:2012, g) a lexicon of specialized terminology along with some specification of the meaning of terms in the lexicon. ISO :2005, h) model that represents a domain and is used to reason about the objects in that domain and the relations between them. ISO/IEC :2016(en), None of these definitions explicitly foresees the possibility of a top-level (in the sense of a domain neutral ) ontology in the sense presupposed by this standard. When they are interpreted in a way that allows for this possibility, however, then definition 3.5 is consistent with all of them. Definition a) is closest to the definition normative in this standard. 3.9 knowledge base combination of an ontology with a collection of data about particulars which terms in the ontology have been used to describe, classify, or connect. NOTE 1: The ontology community associated with OWL has drawn a distinction between an A-box (for assertions ) and a T-box (for terminology ). ABox and TBox statements taken together make up a knowledge base. An A-box contains statements about individuals such as the Planet Earth or patient James McJames. A T-box contains statements about the classes or types represented by terms such as planet, patient, or human being under which such individuals fall. Ontologies are T-box (terminological) artefacts. NOTE 2: An ontology is used to describe, classify, or connect ( annotate or tag ) data in a database when, for example, terms in the ontology are associated with data table column headers, or when a knowledge base is created by extending the ontology graph with nodes representing data entries pertaining to individuals. 10 ISO 2017 All rights reserved

13 3.10 domain a collection of entities of interest to a certain community or discipline EXAMPLES: The domain of agriculture, the domain of cell biology, the domain of aircraft maintenance, the domain of philately. NOTE 1: Compare ISO/IEC 2382: , which defines domain in the context of artificial intelligence as: a specific field of knowledge or expertise. NOTE 2: Entities of interest can include both individuals and classes or types. NOTE 3: The definition is to be interpreted as meaning that a domain is a collection of entities that is narrow in scope. Thus there is no universal domain, to which everything would belong domain ontology an ontology whose terms represent classes or types and, optionally, distinguished individuals in some domain 3.12 category a general class or type that is shared across many different domains and is represented by a domain-neutral term EXAMPLES: Candidate examples of category are: object, attribute, process, spatial and temporal region, and information entity top-level ontology (TLO) an ontology that is created to represent the categories that are shared across a maximally broad range of domains NOTE 1: A top-level ontology is sometimes also referred to as a 'formal ontology', foundational ontology, 'upper level ontology', or 'domain-neutral ontology'. NOTE 2: Top-level ontologies are reference ontologies in the sense of ISO/IEC :2010 [7]. NOTE 3: A top-level ontology may include representations of distinguished individuals that span a broad range of domains, EXAMPLES: actual world, spacetime. NOTE 4: Many upper ontologies incorporate content equivalent to that of a TLO, but within a larger frame within which non-tlo content is also included. This means that the relevant TLO content is not self-standing and thus the ontologies in question cannot serve the purposes of a TLO as documented in this standard. The content in question would, however, constitute a TLO within the terms of this standard if extracted as a self-standing ontology suite of ontologies a collection of ontologies developed in such a way as to be mutually consistent and non-redundant EXAMPLES: See Informative Annex A 3.15 ontology reuse a target ontology D1 reuses a second ontology D2 when some or all of the terms, relational expressions, definitions and axioms of D2 are imported by D1 in such a way that the result of importing preserves the intended meaning of the imported D2 content ISO 2017 All rights reserved 11

14 3.16 downward population a method for ontology creation whereby terms and relational expressions from an existing ontology at a given level of generality are reused in a second ontology at a lower level of generality. EXAMPLE: terms from a tool ontology are reused in a power tool ontology; the latter is a specialization of the former. 12 ISO 2017 All rights reserved

15 4 Conformance 4.1 Overview of conformance This international standard specifies what a top-level ontology is. Conformance to this specification will be demonstrated by providing an implementation comprising the required component parts together with a set of supplementary documents. Both implementation and supplementary documentation shall be in accordance with the requirements set forth in Clause Ontology implementation An implementation that is in conformity with this standard shall have the following parts A natural language document satisfying requirement An OWL 2 DL axiomatization of the ontology satisfying requirement An axiomatization of the ontology in a CL-conformant language satisfying requirement Supplementary documentation satisfying requirement (Conditional) supplementary documentation satisfying requirement Degree of conformance This standard draws a distinction between strict conformance and partial conformance along various dimensions set forth in 4.4. For strict conformance conformance must be claimed for both ontology implementation and supplementary documentation. Component 5.5 is required to establish strict conformance only where a TLO is used as a starting point for definitions for example in the context of a suite of domain ontologies. 4.4 Dimensions of partial conformance Implementation An ontology qualifies as partially conformant if it either (1) satisfies clause 5.2 but not 5.3, or (2) it satisfies both of these clauses but fails to satisfy Breadth of coverage An ontology qualifies as partially conformant along the dimension of breadth of coverage if its documentation provides answers to at least some of the questions listed under 5.4 but not to all of them. ISO 2017 All rights reserved 13

16 5 Requirements for a top-level ontology This international standard specifies requirements for a top-level ontology. Documents submitted under 5.1, 5.4 and 5.5 which use terms defined in clause 3 shall use them in accordance with the definitions there provided. 5.1 TLO as textual artefact The implementation of the TLO shall include a textual artefact represented by a natural language document specifying: (1) a list of domain-neutral terms and relational expressions (also called the signature of the ontology), incorporating identification of primitive terms To remove the possibility of conflict between the TLO and domain ontologies beneath it the TLO shall contain exclusively terms that are domain neutral, thus terms representing categories. Where a TLO is used In conjunction with a suite of domain ontologies created for scientific purposes, for example, inclusion of terms from chemistry or biology in the TLO creates the possibility of conflict with the chemists and biologists who will be responsible for corresponding domain modules. On the other hand, terms representing time, space and spacetime, can be included in a TLO since these extend across all domains. (2) a list of definitions of the meanings of the terms and relational expressions listed under (1) Given the nature of a TLO, a proportion of its terms and relational expressions will be so basic in their meaning that there will be no more easily intelligible expressions on the basis of which they can be defined in a non-circular way. Such terms and relational expressions are called primitives and they can at best be provided with definitions (in the sense of 3.5) that are mere paraphrases. A TLO shall specify which of its terms and relational expressions are primitive in this sense. For all other terms and relational expressions in the TLO, definitions shall be provided which satisfy the conditions that a. they are non-circular b. they form a consistent set These requirements apply both to the natural language definitions and also to the definitions provided in the OWL 2 DL and CL axiomatizations. To ensure non-circularity it is recommended (i) that definitions are formulated as statements of singly necessary and jointly sufficient conditions for the correct application of the defined term, (ii) that logical composition in the expressions forming the natural language counterpart of the signature of the ontology and in the associated natural language definitions should be reflected in corresponding logical composition in the OWL and CL formalizations. EXAMPLES: Examples of logical composition are: temporal quality, non-physical quantity, has-electrolyte-part Consistency of the natural language definitions is shown through the development of the OWL and CL axiomatizations. To ensure consistency of the definitions in the OWL formalization standard reasoners shall be used. To ensure consistency of the definitions in CL semi-automatic procedures such as those described at shall be used. NOTE: Consistency and non-circularity of definitions is a feature which distinguishes ontologies from traditional dictionaries and other lexical resources. Non-circularity excludes not only immediate circularity (where the defined term or 14 ISO 2017 All rights reserved

17 a term with equivalent meaning in the definition) but also mediated circularity (for example where a term is used in the definition of a second term, which is itself used in the definition of the first term). 5.2 Formal representation in the Web Ontology Language (OWL 2 DL) The TLO shall be made available via a machine-readable axiomatization in OWL 2 DL or in some description logic that is designated by W3C as a successor of OWL 2 DL. The signature of the axiomatization shall be identical to the vocabulary of the ontology as specified in 5.1. The axioms should represent the content of the definitions provided under 5.1 to the extent that this is possible given the expressivity of OWL 2 DL. The axiomatization shall satisfy the conformance criteria set forth in [12]. The axiomatization shall be interpretable in the CL axiomatization described in 5.3. NOTE: If more than one formal representation of an ontology is provided which are not logically equivalent, these must form a set linearly ordered in terms of theory strength, where theory A is stronger than theory B when B is interpretable in A, but A is not interpretable in B. Theory B is interpretable in theory A iff the language of B can be translated into the language of A so that every theorem of B is derivable in A. An ontology developed in CL is in this sense stronger than than OWL 2 DL, since the latter is interpretable in the former but not vice versa. Given the differences in expressivity as between OWL 2 DL and CL, it may be necessary to use terms and relational expressions in the OWL axiomatization that are not present in the CL axiomatization. To show interpretability of the former from the latter it will then be necessary to add the corresponding expressions to the CL signature. Such addition shall be a conservative extension of the CL axiomatization, which means that no theorems formulable within the old signature become provable as a result of the extension. NOTE 1: OWL 2 DL is the W3C standard language most widely used in the axiomatization of domain ontologies designed to be used in applications. It is associated with a variety of software tools, including reasoners able to validate ontology consistency. NOTE 2: In the OWL2 DL formalization terms and relational expressions are replaced by IRIs [3] used in accordance with the rules set forth in the OWL Web Ontology Language Guide [4]. The IRIs should be constructed from a base IRI and a local identifier (typically consisting of a unique numeric string followed by a syntactically regimented form of the corresponding term, for example created by use of camel case). It is recommended also that the IRI should resolve to useful information about the term and its referent, including definition, specifications of provenance for term and definition, relevant images or other graphics, synonyms, and translations into other languages. 5.3 Formal representation in a CL-conformant language The TLO shall be made available via an axiomatization in a language conformant to ISO/IEC 24707:2007 Common Logic [1]. EXAMPLES: Languages directly conformant to CL are: Common Logic Interchange Format (CLIF), the Conceptual Graph Interchange Format (CGIF), and the XML-based notation for Common Logic (XCL). An example of a language indirectly conformant to CL is the language of traditional first-order logic (FOL). The signature of the axiomatization shall be identical to the vocabulary of the ontology as specified under 5.1. The axiomatization shall extend the OWL 2 DL axiomatization described in 5.3 in the sense that its intended models extend the models of the OWL 2 axiomatization. The axiomatization shall be validated for soundness and consistency using standard theorem provers. NOTE 1: CL is a logical framework standardized for the purpose of facilitating exchange and transmission of knowledge in computer-based systems. CL is a family of formal languages with a common descriptive semantics. Since CL circumvents differences in formal language syntax by focusing on a shared semantics, translations between distinct formal languages are easier to automate. Logicians and engineers in recent years have been developing automated support for ontologies in CL through tools such as are provided by HETS ( which provides software for ontology-related tasks such as syntax translation, consistency checking and modularization, as well as proof-assistants and common theorem provers. 5.4 Supplementary documentation Supplementary documentation, or references to such documentation in archived publications, shall be provided, ISO 2017 All rights reserved 15

18 specifying how the ontology is used or is intended to be used, specifying how it is shown that the OWL axiomatization specified in 5.4 is logically derivable from the CL axiomatization specified in 5.5. demonstrating the breadth of coverage of the ontology by addressing the questions listed in 5.9 below, It is recommended that in addition there should be provided documentation specifying the criteria that shall be satisfied if a domain ontology is to conform to the TLO in a way that enables the latter to serve as starting point for definitions in accordance with requirement Documentation of the purpose of the ontology The actual or envisaged purpose of the TLO shall be described in detail. EXAMPLES: Examples of uses of a TLO are as a framework: a. for the development of domain ontologies or domain ontology suites; b. for the development of knowledge bases drawing on data from multiple domains; c. for the re-engineering of existing ( legacy ) domain ontologies and similar information artifacts with the purpose of advancing interoperability or to promote clarity of definitions; d. for ontology support for systems integration initiatives (involving both humans and machines) e. for high-level structuring of cross-domain lexical resources such as WordNet Documentation of conformance to the TLO (Conditional conformance requirement) Where, as in examples a.-c. above, the TLO is used in conjunction with other resources in ways which require conformance of these resources to the TLO, documentation is required on the mechanisms used to establish such conformance and to preserve such conformance as resources change. EXAMPLES: Examples of such mechanisms are: direct import: the domain ontology is constructed ab initio by importing BFO into an ontology editor and defining all its upper level terms using BFO as genus. re-engineering: an existing domain ontology created independently of BFO is transformed into an ontology that is conformant re-definition and where necessary re-configuration of its upper zlevel terms and relations Documentation specifying the relation between OWL and CL axiomatizations Documentation shall be provided specifying how it is shown that the OWL axiomatization specified in 5.4 is logically derivable from the CL axiomatization specified in 5.5. EXAMPLE: An example of such documentation would consist in describing how the HETS tool is used to show that the OWL 2 DL axiomatization of an ontology O is interpretable in the CL axiomatization C by showing that any theorem of the former is a theorem of the latter. The process of showing interpretability in a semi-automated manner proceeds first by showing that O has been converted with an automatic syntactic translator into an ontology CL(O) with CL-conformant syntax. Second, by adding translation definitions to C bridging the syntax of C to that of CL(O) yielding the result TR(C). Third, using an automated theorem prover to show that each axiom of O is derived from TR(C) Documentation demonstrating breadth of coverage In order to serve its purpose of supporting interoperability, a TLO is required to provide a starting point for the introduction of the most general terms (root nodes) of ontologies constructed or re-engineered on its basis. The TLO serves consistent development of these ontologies by ensuring that their terms are introduced as specializations of the same set of most general categories. In the simplest case a term in the TLO will provide the genus for the definition of one or more root nodes (nodes of highest generality) within a more specific ontology. 16 ISO 2017 All rights reserved

19 Since a TLO is an absolute starting point for the application of such downward population, the TLO cannot itself be a product of the application of this method. To serve its purpose, a top-level ontology is required to be capable of representing the entities described in a maximally broad range of data sources. Thus, it should include categories, which is to say classes or types which apply across all or across a very broad range of domains. Similarly, a top-level ontology should include relational expressions that enable representation of a broad range of relations among entities in its chosen categories. Different candidate top-level ontologies have made different and sometimes incompatible choices concerning these categories and relations. These choices shall be documented in a way that will justify the claim that the ontology has a sufficiently broad coverage of categories and relations to satisfy the requirements of a TLO as defined by this standard. To this end, the ontology documentation shall provide answers to the questions listed in what follows. Where the ontology does not include categories that cover the areas identified, it should be indicated how the corresponding phenomena will be addressed. EXAMPLE: Examples of how missing coverage could be addressed are: by reference to an additional ontology, whose relation to the TLO is specified; by a description of how the question rests on a presupposition not made by the TLO in question Relation to time and space How do the entities represented in the ontology exist in relation to time? Does the ontology take a bicategorialist view allowing both persisting and occurrent entities, manifesting two distinct modes of existence in time? Does it take a 3-dimensionalist view allowing only entities extended in space? Does it take a 4-dimensionalist view allowing only entities extended in spacetime? How does the ontology deal with (one-, two- and three-dimensional) spatial regions and with (fourdimensional) spatiotemporal regions? EXAMPLES: Spatial boundaries such as the Equator and the North Pole are examples of two- and one-dimensional spatial regions, respectively. The latitude-longitude system and WGS 84 are examples of frames of reference Actuality and possibility How does the ontology deal with what might be the case, rather than what is the case, with what might happen rather than what has happened? Does it support both possible and actual entities? Does it have a treatment of dispositions or tendencies? Does it have a way of dealing with plans or designs that relate to merely potential entities? Realism vs. nominalism How does the ontology deal with issues of classification? Does classification involve merely the existence of certain relations of similarity between certain entities, or is there a relation of instantiation between entities and corresponding classes or types? Are classes of classes allowed? Are types or universals instantiated by the same individuals identical? Eternalism vs. presentism and change over time How does the ontology deal with time and change? ISO 2017 All rights reserved 17

20 Is the ontology eternalist (so that the past and the future exist as well as the present), or is it presentist (so that only the present moment exists), or something else? How does the ontology deal with location, and with change of location? Does the ontology allow for more than one object to occupy exactly the same spatial location at the same time? How does the ontology deal with changes in attributes? Does the ontology recognize a distinction between universals that necessarily apply to a particular for the whole of its existence, and universals that apply only temporarily. EXAMPLE 1: Mammal is an example of a universal that applies to a particular for the whole of its existence. EXAMPLE 2: Lawyer is an example of a universal that applies to a particular temporarily. How does the ontology deal with identity and change of objects over time? EXAMPLE: Persons are an example of objects that can undergo change over time, such as by losing hair, without changing identity Parts, Wholes, Unity and Boundaries How does the ontology deal with relations of parthood? Does it define parthood as a reflexive, transitive, antisymmetric relation, or does it have an alternative formal treatment of parthood? How does it treat the issue of supplementation: if a is a part of b but not identical to b, then there is some part (or some unique maximal part) of b that has no parts in common with a? How does it deal with wholes formed through the summation of parts? How does it deal with relations of continuity where an object has parts between which there is no natural boundary? How does it deal with the factor of unity manifested for example by single objects as opposed to collections of objects? How does it deal with relations of contact where two objects touch, but are not fixed in place? Levels of reality How does the ontology deal with granularity and levels of reality (where grains at one level are parts of grains at higher levels)? Does the ontology treat the material world as being made up of distinguished levels? If yes, what is the relation between such entities and the material of which, at any given time, they are made? EXAMPLE: atoms, molecules, cells, organisms or planets are examples of entities at distinct levels of reality Attributes How does the ontology deal with attributes? NOTE: Attribute here is meant to include what are sometimes referred to as properties, features or characteristics. How do qualitative attributes such as colour or temperature relate to quantities? How do attributes relate to the entities that have or bear them? Does the ontology recognize attributes of attributes? Processes and events How does the ontology deal with processes? Are processes identical to changes? What kinds of processes exist? 18 ISO 2017 All rights reserved

21 Does the ontology allow attributes of processes? Does the ontology recognize a distinction between processes and states? Roles How does the ontology deal with roles? EXAMPLE: The lawyer role and the agent role are examples of roles Participation How does the ontology deal with the relation between processes and the entities that participate in them Causality How does the ontology deal with causality? Abstracta Does the ontology recognize immaterial entities? EXAMPLES: Cavities, numbers, shapes. If not, how does it deal with corresponding data? Information and reference How does the ontology deal with information entities? Does it incorporate a relation of aboutness between information entities and what they are about? If yes, how does the ontology deal with the phenomenon of aboutness in cases where there is no actual entity which a given information entity is about? Does the ontology deal with cases of this sort by recognizing possible worlds? EXAMPLE: Cases of aboutness where there is no corresponding actual entity may arise where plans for the future are being made Artefacts and socially constructed entities Which categories in the ontology would be used to deal with artefacts? EXAMPLE: Engineered items are examples of artefacts. Which categories in the ontology would be used to deal with socially constructed objects such as money? Which categories in the ontology would be used to deal with agreements, responsibilities, or permissions? ISO 2017 All rights reserved 19

22 Informative Annex: Examples of ontology suites Table 1 below lists example of ontology suites proposed by different communities since 1998, ordered by year of first archival publication. Each such suite represents an attempt by developers of multiple ontologies covering different but related domains of entities to ensure discoverability and mutual consistency between the ontologies being developed. A common method to achieve such coordination involves the application of a hub-and-spokes strategy, resting on a highly general domain-neutral hub, together with successive layers of spokes comprising domain ontologies built out of terms defined as specializations of terms contained in the hub. Table 1. Examples of ontology suites Ontology suite Domain Year URL Hub Toronto Virtual Enterprise (TOVE) enterprise modeling Yes Gene Ontology (GO) attributes of gene products ml No Gramene: Trait and Gene Ontologies for Rice Semantic Web for Earth and Environmental Terminology (SWEET) Legal Informatics Ontologies (LRI- Core) Open Biomedical Ontologies (OBO) Foundry Performance Simulation Initiative (PSI) Ontology Suite Networked Ontologies from the Fisheries Domain Marine Metadata Interoperability Project Infectious Disease Ontology (IDO) suite Semantic Publishing and Referencing Ontologies (SPAR) plant science Yes earth and environmental sciences legal informatics (Raskin).pdf Yes life sciences Yes engineering design and performance fisheries _ _29 oceanography No infectious diseases document description _ _5 No Yes No Yes No 20 ISO 2017 All rights reserved

23 Bibliography 1. ISO/IEC 24707:2007 (Information technology Common Logic (CL): a framework for a family of logicbased languages) 2. W3C Recommendation OWL 2 Web Ontology Language Document Overview (Second Edition), 11 December M. Duerst; M. Suignard. Internationalized Resource Identifiers (IRIs). RFC 3987 January Proposed W3C Standard OWL Web Ontology Language Guide ( ), last accessed August 1, W3C Recommendation OWL 2 Web Ontology Language Structural Specification and Functional- Style Syntax (Second Edition), 11 December 2012, / 6. W3C Recommendation Linked Data Platform / 7. ISO/IEC 19763, Information Technology Metamodel Framework for Interoperability (MFI) ISO 2017 All rights reserved 21