1995, Nicola Guarino
ABSTRACT
The word “ontology” has recently gained a good popularity within the knowledge engineering community. However, its meaning tends to remain a bit vague, as the term is used in very different ways. Limiting our attention to the various proposals made in the current debate in AI, we isolate a number of interpretations, which in our opinion deserve a suitable clarification. We elucidate the implications of such various interpretations, arguing for the need of clear terminological choices regarding the technical use of terms like “ontology”, “conceptualization” and “onto
logical commitment”. After some comments on the use “Ontology” (with the capital “o”) as a term which denotes a philosophical discipline, we analyse the possible confusion between an ontology intended as a particular conceptual framework at the knowledge level and an ontology intended as a concrete artifact at the symbol level, to be used for a given purpose. A crucial point in this clarification effort is the careful analysis of Gruber's definition of an ontology as a specification of a conceptualization
单词“本体”最近在知识工程社区中得到很高的关注。但是由于经常以不同的方式使用，它的含义确趋于模糊。因此，我们应该得到适当的澄清。我们说明不同解释的含义，对术语“ontology”,"conceptualization","ontological commitment"进行清晰地说明。我们分析了本体可能出现的混乱，一方面趋于在知识级作为特殊的概念框架，另一方面趋于在符号级作为具体的。区分时关键点在于仔细分析gruber对本体的定义作为概念化的描述。
1 Introduction
The word “ontology” has recently gained a good popularity within the knowledge engineering community,especially in relation with the recent ARPA knowledge sharing initiative [14, 11, 13, 4, 6, 7, 12]. However, its meaning tends to remain a bit vague, as the term is used in very different ways. Limiting our attention to the various proposals made in the current debate within the knowledge sharing community, we can isolate the different interpretations reported in Fig. 1 below, which in our opinion deserve a suitable clarification.
1. Ontology as a philosophical discipline
2. Ontology as a an informal conceptual system
3. Ontology as a formal semantic account
4. Ontology as a specification of a “conceptualization”
5. Ontology as a representation of a conceptual system a logical theory
5.1 characterized by specific formal properties
5.2 characterized only by its specific purposes
6. Ontology as the vocabulary used by a logical theory
7. Ontology as a (meta-level) specification of a logical theory
本体最近被高度关注，但是，它的含义变得模糊，表1中列出了不同的解释：
1. 本体是一个哲学学科
2.本体是一个非正式概念上的系统
3.本体是一个形式语义描述
4.本体是一个概念化名词的描述
5.本体是一个经过逻辑理论的概念化系统表示
5.1 由特殊的正式属性表示
5.2 由其特殊的目的表示
6.本体是逻辑理论的一个词汇
7.本体是一个逻辑理论的元数据级描述
The interpretation 1 is radically different from all the others, and its implications are discussed in the next section. The current debate regards the interpretations 2-7: 2 and 3 conceive an ontology as a conceptual “semantic” entity, either formal or informal,while according to the interpretations 5-7 an ontology s a specific “syntactic” object. The interpretation 4, which has been recently proposed as a definition of what an ontology is for the AI community [4, 5], is one of the more problematic, and it will be discussed n detail in the present paper. It may be classified as “syntactic” but its precise meaning depends on the understanding of the terms “specification” and “conceptualization”.
第1个解释不同于其它，在下一章讨论。2-3将本体看作一个概念上的语义实体，既不正式也不随便。5-7将本体看作是语法对象。4认为在AI社区中，它可能被划分到语法，但是其精确的含义依赖于"specification"和"conceptualization"。
According to interpretation 2, an ontology is the (unspecified) conceptual system which we may assume to underly a particular knowledge base. Under interpretation 3, instead, the “ontology” which underlies a knowledge base is expressed in terms of suitable formal structures at the semantic level, like for instance those described in [8, 17].In both cases, we may say “the ontology of KB1 is different from that of KB2”.
根据解释2，本体是一个不确定的概念上的系统，我们假设其位于一个特殊的知识库。解释3则是在语义级用适当的正式结构表达的知识库，具体可参考[8,17]。
Under interpretation 5, an ontology is nothing else than a logical theory. The issue is whether such a theory needs to have particular formal properties in order to be an ontology (for instance, we may impose it must be a “Tbox”) or, rather, it is the intended purpose which lets us consider a logical theory as an ontology. The latter position is being supported for instance by Pat Hayes, which in recent e-mail discussions argued that an ontology is an annotated and indexed set of formal assertions about something: “leaving off the annotations and indexing, this is a collection of assertions: what in logic is called a theory”.
解释5认为，本体其实是一个逻辑系统。其讨论是为了表示一个本体，是否需要有一些特殊的形式化的属性，其本质是要让大家认为一个逻辑理论可以作为一个本体。pat hayers对本体是一个有关事物的有序和带注释的正式断言集合的观点进行了讨论：“抛开注释和有序，本体仅是一个断言的集合：内在逻辑称之为理论”
According to interpretation 6, an ontology is not viewed as a logical theory, but just as the vocabulary used by a logical theory. Such an interpretation col-
lapses into 5.1 if an ontology is thought of as a specification of a vocabulary consisting of a set of logical definitions. We may anticipate that interpretation 4
collapses into 5.1, too, when a conceptualization is intended as a vocabulary; we shall see however that the problem is how to make clear the meaning of the term
“conceptualization”.
根据解释6，本体不应该看作逻辑理论，但是应作为逻辑理论的一个词汇。如果本体被看作是由逻辑定义集合中的一个描述，则与解释5.1一致。如果有意将概念化作为一个词汇，解释4可与5.1合并；问题是如何使"conceptualization"的含义更清晰。
Finally, under interpretation 7, an ontology is seen as a (meta-level) specification of a logical theory, in the sense that it specifies the “architectural components” (or “primitives”) used within a particular domain theory. This point of view is maintained in [18] and, in slightly different form, in [10]. Wielinga and colleagues argue that it is the ontology which specifies, for a theory where some formulas have the form of mathematical constraints, what a constraint is and how it differs from a formula of another kind; Mark argues that an ontology is “a representation of components and their allowed interactions, with the purpose of providing an explicit framework in which to elaborate the rest of the system...”
最后，解释7，本体被看作是逻辑理论元数据级的描述，
We shall try to elucidate in this paper the implications of such various interpretations, arguing for the need of clear terminological choices regarding the technical use of terms like “ontology”, “conceptualization” and “ontological commitment” within the knowledge engineering community. First we propose to use “Ontology” (with the capital “o”) as a term denoting a philosophical discipline, then we analyse a number of possible senses of the term “ontology” (with the lowercase “o”) where the term is somehow related to specific knowledge bases (or logical theories) designed with the purpose of expressing shared (or sharable) knowledge.
我们试图在本文中说明不同解释的含义，讨论在知识工程社区，正确的使用术语“ontology”,"conceptualization","ontological commitment"
A starting point in this clarification effort will be the careful analysis of the interpretation 4 adopted by Gruber. The main problem with such an interpretation is that it is based on a notion of conceptualization (introduced in [3]) which doesn’t fit our intuitions, as has been noticed in [8]: according to Genesereth and Nilsson, a conceptualization is a set of extensional relations describing a particular state of affairs, while the notion we have in mind is an intensional one, namely something like a conceptual grid which we superimpose to various possible states of affairs. We propose in this paper a revised definition of a conceptualization which captures this intensional aspect, while allowing us to give a satisfactory interpretation to Gruber’s definition.
首先对gruber采用的解释4进行仔细分析。主要问题在于这种解释是基于概念模型的观点，而不是我们的直觉。Genesereth 和Nilsson认为，概念模型是一个描述事务特殊状态的外部联系的集合，同时大脑中的观点是内部的，也就是事物好象概念格，我们可以将事务多个不同的状态重叠。在本文中，我们对概念模型中的获取内部方向，提出了一个改进的定义，同时允许我们对gruber的定义给出满意的解释。
2 Ontology and Ontologies
The first important distinction in the list of interpretations given in the previous section is between interpretation 1 and all the others. We stipulate that when we refer to an ontology (with the indeterminate article and the lowercase initial) we refer to a particular determinate object (whose nature may vary in dependence of the choice among interpretations 2-7), while speaking of Ontology (without the indeterminate article and with the uppercase initial) we refer to a philosophical discipline, namely that branch of philosophy which deals with the nature and the organisation of reality. Ontology as such is usually contrasted with
Epistemology, which deals with the nature and sources of our knowledge2.
当我们提到本体(第一个字母o小写)，我们是指一个特殊确定的对象(其特征可能依赖于解释2-7)。当我们提到的本体(第一个字母o大写)，我们是指一个处理有关自然和现实组织的哲学学科。本体通常与知识论进行对比，知识论是一个关于自然和知识的起源的学科。
Aristotle defined Ontology as the science of being as such: unlike the special sciences, each of which investigates a class of beings and their determinations, Ontology regards “all the species of being qua being and the attributes which belong to it qua being” (Aristotle, Metaphysics, IV, 1). In this sense Ontology tries to answer to the question: What is being? or, in a meaningful reformulation: What are the features common to all beings?
亚里斯多德将本体定义为一个这样的科学：不象特殊科学研究一个对象的起源和终点，本体关注“所有存在的物种和属于物种的属性”。本体试图回答以下问题：存在是什么？区别于其它存在的特征是什么？
This is what nowadays one would call General Ontology, in contrast with the various Special or Regional Ontologies (of the Biological, the Social, etc.). This
distinction corresponds to the Husserlian one between Formal Ontology and Material Ontology [1]. But the Husserlian notion of “formal” does not involve only
generality. For Husserl, the task of Formal Ontology is to determinate the conditions of the possibility of the object in general and the individuation of the requirements that every object’s constitution has to satisfy.
和专业本体(比如生物学，社会学等)相比，这就是通常说的本体。这符合Husserlian提到的形式本体和物质本体的差别。但是，Husserlian提到的formal并不仅包含一般性。Husserl提到，形式本体的任务是决定对象可能的条件和构造满足对象需求的个体。
Recently, Nino Cocchiarella defined Formal Ontology as the systematic, formal, axiomatic development of the logic of all forms and modes of being [2]. The connection of Cocchiarella’s definition with the Husserlian notion is not clear, and, in general, the genuine interpretation of the term “formal ontology” is still a matter of debate [16]. However, Cocchiarella’s definition is in our opinion particularly pregnant, as it takes into account both meanings of the adjective “formal”:on one side, this is synonymous of “rigorous”, while on the other side it means “related to the forms of being”. Therefore, what Formal Ontology is concerned
in is not so much the bare existence of certain objects,but rather the rigorous description of their forms of being, i.e. their structural features. In practice, Formal Ontology can be intended as the theory of the distinctions, which can be applied independently of the state of the world, i.e. the distinctions：
• among the entities of the world (physical objects,events, regions, quantities of matter...);
• among the meta-level categories used to model the world (concept, property, quality, state, role,part...).
In this sense, Formal Ontology, as a discipline, may be relevant to both Knowledge Representation and Knowledge Acquisition [7].
最近，Nino Cocchiarella用系统的、正式的、公理化的观点定义正式本体论。通常正式本体论的真正解释仍然在讨论。Cocchiarella认为formal有两个含义：一方面是指严密的，另一方面是指“与客观存在形式相关”。因此，正式本体论不仅仅关心某个对象，而且关心客观存在的形式上的严密描述，比如它们的结构特征。实际上，正式本体论可以看作关注差异的理论，比如这些差异有：
. 在现实世界的实体中(物理对象，事件，地区，事物质量...)
. 在元数据级范畴对世界进行建模(概念，属性，质量，状态，角色，部分)
正式本体论可作为一个规则，用于知识表示和知识获取。
3 Kinds of Ontologies
Let us now refine the technical meaning of the word “ontology” when — within the knowledge engineering community – it is used to denote a particular object rather than a discipline. Here a possible confusion arises between an ontology intended as a particular conceptual framework at the semantic level (interpretations 2-3) and an ontology intended as a concrete artifact at the syntactic level, to be used for a given purpose (interpretations 4-7). This is an important distinction, and it is evident that we cannot use the same technical term to denote both things. In the current practice, however, the term “ontology” is used ambiguously with both meanings, either to refer to (various kinds of) symbol-level artifacts, or to their
conceptual (or semantical) counterparts3. Therefore,rather than insisting on a unique precise meaning for such a term, what we propose is to adopt different technical terms to refer explicitly to the two levels, while tolerating an ambiguity in the interpretation of the term “ontology” (with the lowercase initial).
我们现在定义本体单词的含义，它用于标注一个特殊对象比一个规则要多得多。这里有个困惑：本体用于语义层的特殊概念框架(解释2-3)，或者为了给定的目的(解释4-7)而用于语法层的具体人工作品。这个区分很重要，我们不能使用同样的单词去标记两个事物。我们必须用不同的单词对其进行区分。
We shall use the term conceptualization to denote a semantic structure which reflects a particular conceptual system (interpretation 3 in Fig. 1), and ontological theory to denote a logical theory intended to express ontological knowledge (interpretation 5). The underlying intuition is that ontological theories are designed artifacts, knowledge bases of a special kind which can be read, sold or physically shared. Conceptualizations, on the other hand, are the semantical counterpart of ontological theories. The same ontological theory may commit to different conceptualizations, as well as the same conceptualization may underlie different ontological theories. The term “ontology” will be used ambiguously, either as synonym of “ontological theory” or as synonym of “conceptualization”. We need only to be consistent to the choice made within the same statement.
我们使用概念化去标记词义结构，映射特殊的概念系统。我们使用本体理论去标记逻辑理论去表达本体的知识(解释5).基本直觉是本体理论是人工作品、可以读的基于特殊种类知识、固定和物理共享。概念化的另一方面是本体理论的语义副本。同样的本体理论可能提交到不同的概念化，同样的概念化可能位于不同的本体理论。
4 Kinds of Conceptualizations
Let us notice first that the use of the term “ontology” as related to an ontological theory is compatible with Tom Gruber’s definition of an ontology as “an explicit specification of a conceptualization”, since it should be clear that an “explicit” object is a concrete, symbollevel object. The problem with Gruber’s definition,however, is that it relies on an extensional notion of conceptualization” [3] which, while being compatible with the preliminary characterization given in the previous section, does not fit our purposes of defining what an ontology is. We have already pointed to this problem in [9] ; we shall discuss it here in detail, proposing an alternative, intensional definition of “conceptualization” which satisfies our needs.
让我们先关注单词“本体”，本体理论和Tom Gruber对本体的定义“一个严格的概念化描述”是兼容的，都是具体和符号化的严格描述对象。Tom Gruber定义的问题在于，它依赖于对概念化进行补充。当它与前面章节给出的起始特征兼容时，定义本体是什么将没有达到我们的目的。我们已经指出了这个问题；我们需要在这里详细的讨论，而不是加强对“概念化”的定义如何满足我们的需要。
Let us consider the example given by Genesereth and Nilsson. They take into account a situation where two piles of blocks are resting on a table (Fig 3). According to the authors, a possible conceptualization of this scene is given by the following structure:
<{a, b, c, d, e}, {on, above, clear, table}>
where {a, b, c, d, e} is a set called the universe of discourse, consisting of the five blocks we are interested in, and {on, above, clear, table} is the set of the relevant relations among these blocks, of which the first two, on and above, are binary and the other two, clear and table, are unary4. The authors make clear that
objects and relations are extensional entities. For instance, the table relation, which is understood as holding of a block if and only if that block is resting on the table, is but the set {c, e}. It is exactly such an extensional interpretation which originates our troubles.
我们看一下Genesereth and Nilsson给的例子。他们认为一个状态有两个块。作者想表示的概念用如下结构表示：
<{a, b, c, d, e}, {on, above, clear, table}>
当{a, b, c, d, e}是一个集合，称之为论域，由5个我们感兴趣的块构成，{on, above, clear, table}是一个之些块的相关联系.作者清晰的表示对象和联系是扩展的实体。比如，表格关系，
