Trong những người tham gia thí nghiệm thứ hai được yêu cầu để mở rộng bản thể học được xây dựng trong vòng ï ¬ rst. Trong giai đoạn này, các hình thức đại diện cho bản thể học ï ¬ xed. Các khái niệm chung nhất đã được ban đầu đề xuất, để tránh các cuộc thảo luận triết học. Đối với vòng thứ hai chỉ xây dựng đối số, ví dụ, ví dụ truy cập, | 250 APPLYING SEMANTIC TECHNOLOGY TO A DIGITAL LIBRARY account when faced with trade-offs in designing systems and to be further tested by users reaction to real semantic digital library systems. . IMPLEMENTING SEMANTIC TECHNOLOGY IN A DIGITAL LIBRARY . Ontology Engineering A well-designed ontology is essential for a successful semantic application. Within SEKT we are adopting a layered approach. In the lower layers we have a general ontology which we call Proton PROTo Ontology http . The classes in this ontology are a mixture of very general for example Person Role Topic TimeInterval and classes which are more specific to the world of business for example Company PublicCompany MediaCompany. See Chapter 7 for more detail. Above this we have the PROTON Knowledge Management ontology which contains classes relating to knowledge management. Examples are UserProfile and Device. Finally each of our three case studies has its own domain-specific ontology. In the case of the digital library this will contain classes relating to the specifics of the library for example to the particular information sources available. A strength of an approach based on the use of an ontology language such as OWL is the ability to accommodate distributed ontology creation activities for example through defining equivalences. Nonetheless where possible the creation of duplicate ontological classes should be avoided and where appropriate we make use of existing well-established ontologies for example Dublin Mention has been made of the use of a topic hierarchy. Within PROTON there is a class Topic . Each individual topic is an instance of this class. However frequently a topic will be a sub-topic of another topic for example in the sense that a document about the former should also be regarded as being about the latter. Since topics are instances not classes we cannot use the inbuilt subclass property but must define a new property subTopic. Such a .
