Composing and decomposing ontologies: a logic-based approach

在计算机科学中，本体被用来为感兴趣的领域提供一个公共词汇，以及根据词汇和它们之间的关系构建的术语的含义的描述，就像在百科全书中一样。在这个意义上，本体越来越多地被用于知识管理系统、医学和生物信息学，并将在语义网和网格中发挥关键作用。为了便于计算机访问，现代本体被用基于描述逻辑(DLS)的本体语言来表示，例如OWL。目前的应用正在导致大型和复杂的本体的发展(有时超过300,000个不同的术语)。设计和维护这样的本体是一项复杂的任务，而且必须小心地执行，以使本体有用。它可能涉及一组本体工程师和领域专家合作，以设计本体，更新它以反映领域中的变化/发展，并将其与其他本体集成，以便覆盖更大的领域。使用OWL等基于DL的本体语言有两个优点：(1)它们具有明确的语义，这意味着术语的含义是以明确的方式指定的，从而使人们能够共享对本体的理解；(2)我们可以利用DL Reasper的推理服务来进行本体工程和使用。这些服务的可用性已经改变了本体工程师的工作方式。然而，这些服务对于工程和维护大型本体是不够的，尤其是在协作的情况下。对本体的本地更改以及此类更改之间的交互可能会产生目前无法预测的高度非本地影响。检查这些影响的唯一时间是在根据所有拟议的改变做出改变之后。即使这样，也有一些变化的影响是使用当前的推理服务套件无法检测到的。总之，本体工程的状态与结构化编程技术出现之前的软件工程状态非常相似：本体不能被分解成完全不同的组件，我们无法预测(局部)变化的范围，如何重用本体的部分或安全地组合它们是悬而未决的问题。在软件工程中，建立了人工文档和严格的过程限制，以及构建程序的初步机制。随着这些机制变得越来越复杂，它们已经导致了用于转换程序以提高性能、理解和重用的新的自动化技术。令人信服的是，以受控的方式组合和分解本体的方法和算法支持将是支持协作本体工程和重用的关键。更确切地说，我们计划为(T1)开发具有接口(以及对其使用的可接受限制)的本体开发方法和算法支持，以保证，如果这样的本体与其他本体组合，它既不会破坏组成它们的本体，也不会被组成它们的本体破坏；(T2)评估一组给定本体的组合的结果，这些本体可能已经以完全不受限制的方式构建；(T3)将大型本体分解为可以以受控方式编辑的模块。事实上，该项目的一个目标是提供上述(T1)--(T3)的严格但实用和有用的正式规范。只是在最近才进行了这方面的研究，提出者已经为其实际发展做出了一些开创性的贡献。拟议的方法是这一工作的延续，即它以逻辑为基础，以保守延拓的概念为基础。

In computer science, ontologies are used to provide a common vocabulary for a domain ofinterest together with descriptions of the meaning of terms built from the vocabulary and relationships between them, like in an encycopedia. Ontologies in this sense are increasingly used in knowledge management systems, medical and bio-informatics and are set to play a key role in the semantic web and grid. In order to be computer-accessible, modern ontologies are formulated in an ontology language based on description logics (DLs) such as OWL. Current applications are leading to the development of large and complex ontologies (sometimes more than 300,000 different terms). Engineering and maintaining such ontologies is a complex task, and it has to be carried out with care for the ontology to be of use. It may involve a group of ontology engineers and domain experts co-operating in order to design the ontology, update it to reflect changes/developments in the domain, and integrate it with other ontologies so as to cover larger domains. Using a DL based ontology language such as OWL has two advantages: (1) they have an unambiguous semantics , which means that the meaning of terms is specified in unambiguous way, thereby enabling shared understanding of an ontology; and (2) we can make use of reasoning services of DL reasoners for ontology engineering and usage. The availability of these services has already changed how ontology engineers work. However, these services are not sufficient for engineering and maintaining large ontologies, especially in the collaborative case. Local changes to an ontology, and interactions between such changes, can have highly non-local effects that are currently unpredictable. The only time to examine these effects is after the changes have been made, in the light of all the proposed changes. And even then there are changes whose impact is not detectable using the current suite of reasoning services. To sum up, the state of ontology engineering is very similar to the state of software engineering before the advent of structured programming techniques: ontologies cannot be decomposed intosemantically distinct components, we cannot predict the scope of a (local) change, and how to re-use parts of ontologies or safely compose them are open problems. In software engineering,human documentation and rigorous process restrictions were put into place, as well as preliminary mechanisms for structuring programs. As these mechanisms have grown more sophisticated, they have led to new automated techniques for transforming programs for performance, understanding, and re-use. It has been convincingly argued that methodologies and algorithmic support for composing anddecomposing ontologies in a controlled way will be the key to supporting collaborative ontology engineering and re-use. More precisely, we plan to develop methodologies and algorithmic support for (T1) developing ontologies with interfaces (and acceptable restrictions on their usage) which guarantee that, if such an ontology is composed with other ontologies, it neither corrupts nor is corrupted by the ontologies they are composed with; (T2) evaluating the consequences of the composition of a set of given ontologies which may have been built in a completely unrestricted way; (T3) decomposing a large ontology into modules that can be edited in a controlled way.Above, terms such as ``in a controlled way'', ``corrupted ontology'', and ``consequence'' are deliberately left rather vague. Indeed, one goal of this project is to provide rigorous but practical and useful formal specifications of (T1)--(T3) above. It is only very recently that research in this direction has been carried out and the proposers have already made some pioneering contributions towards their actual development. The proposed approach is a continuation of this line of work, i.e., it is logic-based and founded on the notion of conservative extensions .