Automatic Construction of Ontology

本体作为一种词汇系统，对自然语言处理具有重要意义。构建本体论通常需要付出巨大的努力。尤其是关于科学技术的本体论很难制作，因为随着科学技术的进步，词汇量不断增加。我们的目标是给出一种自动构建科技本体的过程。首先，我们给出了本体的数学基础。我们将本体定义为一个有序集，并将本体引入到其中。我们给出了本体的一些数学性质，并开发了一个从观察到的开集集合构建本体的过程。接下来，我们尝试从Inspec磁带中摘要的句子中派生出本体。我们将具有相同属性形容词的主语集合视为开放集合，并从以下形式的句子中提取：主语+be+定语-形容词。然而，很少有几对集合是…的在包含关系中有更多的内容。然后，我们直接从“主语+BE+冠词+本体”形式的句子中提取主语和名词对作为ISA关系。生成的本体包含较长的名词序列，这些实验表明，问题在于摘要中缺乏常识知识。人们可以通过使用现有的本体来补充这些知识，例如WordNet。然而，通用本体论作为常识性知识在科技文献中的应用是值得怀疑的。在构成“比较A和B”句型的句子中，名词短语A和B是“可比较的”。因此，我们假设A和B中的中心名词在某种意义上是相似的，因为它们在本体论上有共同的祖先。使用WordNet进行的实验结果表明，从句子中提取的对中有75%在WordNet中具有共同的祖先。这25%的配对不在本体论上的主要原因是诸如数据、结果之类的词经常被省略。

Ontology as a vocabulary system is important for natural language processing. Constructing the ontology generally requires a great effort. Especially, the ontology about science and technology is difficult to make, since the vocabulary increases continuously according to advances in science and technology. Our goal is to give a procedure for automatically constructing the ontology about science and technology.At first we gave a mathematical basis of the ontology. We defined the ontology to be an ordered set, and introduced ontology into it. We showed some mathematical properties on the ontology, and developed a procedure to build the ontology from the observed collection of open sets.Next, we tried to derive the ontology from the sentences of the abstracts in INSPEC tapes. We considered as open sets the sets of subjects which takes the same attribute-adjective, and extracted from the sentences of the form : 'Subject+be+attribute-adjective'. However, thereare few pairs of sets which are … More in the inclusion-relation. Then, we extracted pairs of subjects and nouns as the ISA-relation directly from the sentences of the form : 'Subject+be+article+noum'. The resulting ontology contains a relatively long sequences of nouns.These experiments tells that the problem is the lacking of the common sense knowledge in the abstracts. One can complement such knowledge by using existing ontology, such as WordNet. However, it is doubtful that the general purpose ontology is useful as the common sense knowledge in the scientific and technical documents. In the sentences that form the pattern 'compare A with B', the noun phrases A and B are 'comparable'. Therefore we assumed that the head nouns in A and B are 'similar' in the sense that they have a common ancestor in the ontology. Experimental results using WordNet shows that 75% of the pairs extracted from the sentences have a common ancestor in WordNet. The reason why the 25% pairs are not on the ontology is mainly due to the fact that the words such as 'data', 'result'are frequently omitted. Less