Anatoly Levenchuk (ailev) wrote,
Anatoly Levenchuk
ailev

Отпускное

Меня тут спросили, как я использую слово "онтология". А так же, как и все. Онтологию я подразумеваю не какую-то особую, но это и не просто классификация (т.е. таксономия). Различия между тезаурусами, таксономиями, онтологиями до сих пор существенно размыты (см., например, http://www.metamodel.com/article.php?story=20030115211223271, где онтологией действительно называют все что угодно и слайд 11 из http://www.idi.ntnu.no/emner/tdt4215/slides/TDT4215-Ontology.pdf (где показан целый спектр "онтологий"), но в последнее время все большее распространение получают другие определения этих терминов: http://www.ontopia.net/topicmaps/materials/tm-vs-thesauri.html (где делается уже замечание, что не онтологиями, а тезаурусами обзывают что угодно), http://www.govtalk.gov.uk/documents/Tomatoes%20are%20not%20the%20only%20fruit%202005-05.pdf (где онтология объявляется "сумасшедшим тезаурусом").

Статистику этих словоупотреблений у профессиональных онтологов можно найти тут: http://ontolog.cim3.net/file/work/OntologySummit2007/survey/wip/ResponseAnalysis-all-terms.html

А вот в определениях из текста стандарта ISO 15926-4:2007 (Annex F) прямо говорится, что онтологии попадают под определения тезаурусов, таксономий, словарей и т.д. (потому как могут всех их выразить), но онтологии кроме того могут выразить еще и факты. А поскольку эти определения (controlled vocabulary, taxonomy, thesaurus, ontology, ontology language) попали в стандарт ISO 15926, хорошо известный многим онтологам, то понимание этих терминов будет все сильнее соответствовать определениям из этого стандарта. Поэтому приведу их тут полностью (тем более, что в Сети их нет):

controlled vocabulary: A controlled vocabulary is a list of terms which has been enumerated explicitly. This list is controlled by, and is available from, a controlled vocabulary registration authority. Each term in a controlled vocabulary should have an unambiguous, non-redundant definition of the thing to which the term refers. This is a design goal which may not be true in practice. It depends on how strict the controlled vocabulary registration authority is regarding registration of terms into a controlled vocabulary. At a minimum, the following two rules should be enforced:
- If the a term outside a controlled vocabulary is commonly used to refer to different things in different contexts, then the term within the controlled vocabulary is qualified to resolve this ambiguity.
- If multiple terms are used to refer to the same thing, then one of the terms is identified as the preferred term in the controlled vocabulary and the other terms are listed as synonyms or aliases.

taxonomy: A taxonomy is a collection of things organized into a hierarchical structure.

NOTE 2 If each thing in a taxonomy has a term assigned to it, then the collection of things, with their terms is also a controlled vocabulary.
Each thing in a taxonomy is in one or more parent-child relationships to other things in the taxonomy. There may be different types of parent-child relationships in a taxonomy (e.g., whole-part, genus-species, type-instance), but good practice limits all parent-child relationships to a single parent to be of the same type. Some taxonomies allow poly-hierarchy, which means that a thing can have multiple parents. This means that if a thing appears in multiple places in a taxonomy, then it is the same thing. Specifically, if a thing has children in one place in a taxonomy, then it has the same children in every other place where it appears.

thesaurus: A thesaurus is a controlled vocabulary is a network of relationships between the terms. A thesaurus uses associative relationships in addition to parent-child relationships. The expressiveness of the associative relationships in a thesaurus vary and can be as simple as “related to term” as in “term A is related to term B”.

ontology: An ontology is a theory about what exists within a domain. An ontology is specified by a collection of things which includes classes (entity class define in ISO 15926-2), individual things (entity thing defined in ISO 15926-2), and relationships between things. A fact within the domain can be recorded by reference to the things within the ontology. From a set of facts recorded using an ontology, it may be possible to deduce further facts.

NOTE 3 If each thing in an ontology has a term assigned to it, then the collection of things, with their terms is also a thesaurus.
NOTE 4 The word “ontology” is sometimes incorrectly used as a synonym of “controlled vocabulary”, “taxonomy” or “thesaurus”. An ontology may also be all of these things. An ontology is distinguished from a taxonomy by having the ability to record facts.
A “foundation ontology”, “base ontology” or “upper ontology” is an ontology which is useful for a wide range of different activities. Such an ontology allows the recording of basic facts, such as the names of things and whole-part relationships. A “domain ontology” is an ontology which is useful for recording information with a particular scientific or engineering discipline. A “domain ontology” is often an extension of a “foundation ontology”, but need not be.
An ontology contains rules about what is possible, and hence about what is a valid fact. When exchanging information, there needs to be an agreement to use a specific ontology.

ontology language: An ontology language is a syntax which is used to record an ontology. Associated with an ontology language, there must also be a syntax which enables an ontology to be used to record a fact. Often, the same syntax is used for both purposes.
The content of an ontology may be limited by the expressiveness of the ontology language used to record it.

NOTE 5 Often an ontology language contains a foundation ontology ‘hard wired’ within it. This is the case for OWL ‘Web Ontology Language’ and ISO 15926-2.

A reference data library which complies with this part of ISO 15926 is necessarily a controlled vocabulary. Depending upon its content, such a reference data library may also be a taxonomy and an ontology.

NOTE 6 This part of ISO 15926 says that:
− Each item shall have exactly one designation.
− If an item is commonly identified by one or more English language terms, then it is recommended that one of these be selected as the designation.
A reference data library which complies with this part of ISO 15926 can be recorded using OWL and ISO 15926-2. Therefore, a reference data library which complies with this part of ISO 15926 can contain an ontology within the capability of these ontology languages.
NOTE 7 This part of ISO 15926 also defines a spreadsheet representation of a reference data library. This spreadsheet format does not have all the capabilities of OWL and ISO 15926-2.

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Наши старые знакомые IFC, STEP и ISO 15926 стремятся слиться в едином порыве в недрах W3C -- сделать веб-онтологию для моделирования продуктов (http://www.w3.org/2005/Incubator/w3pm/). Свеженькая инициатива, 6 мая 2008г..

Что такое "продукт": A product can be a ‘one-of-a-kind’, such as (typically) a building, ship or process plant, or a mass produced item, such as a car, refrigerator, or notebook computer. In principle our approach will be valid for both situations equally. A Product will in general span more than one supply in the supply-chain.

Подробненько планы этой группы изложены тут: http://www.w3.org/2005/Incubator/w3pm/charter. Планы вполне шапкозакидательные.

С этими стандартами описания заводов/продуктов/сервисов мы еще поразвлекаемся, их история только-только начинается. Пора писать standard quagmire и в этой области тоже.

Забавно, что все эти стандарты пока чураются описания собственно процессов, за редкими исключениями. Песня будет, когда процессные стандарты начнут склеиваться с продуктовыми.
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Вот такой у меня отпуск :)
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