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Introduction
Time is ubiquitous, yet the conception of time is not necessarily absolute. In most cases people conceive of time on the basis of the culture and the society they live in. The Russian sociology professor Pitirim Sorokin defines the concept of socio-cultural time that exists independently of the concept of time as it is understood in natural science and that is necessarily culture dependent [82].
Consider the time concept ‘day’. How long is one day? Is it twenty four hours, is it as long as there is daylight outside, or is it so long as the working or school hours? The answers depend on our socio-cultural context. A day may be all those hours that a student has to spend at school or at the university, for a businessman a day can consist of the time at work, which can be a “successful day” or a “profitable day”, and for a patient, who needs to stay at the hospital “for one day”, a day is most probably twenty four hours. Merriam Webster’s dictionary defines eight such interpretations for the time concept of day. Now, consider ‘weekend’. In most western cultures weekend corresponds to the two consecutive days of Saturday and Sunday, whereas in most Middle Eastern cultures weekend is Friday and Saturday. Hence, there are at least two different ways how people conceive of weekend.
The socio-cultural context dependent conception of time, like many other conceptions, is implicitly present in people’s minds. That is, instead of being outspoken, it will be assumed that the others share the same conception. For example, when two citizens of a Middle Eastern country, say Israel, talk about weekend they take it for granted that Friday and Saturday is meant and understood. Yet, is it feasible to assume the same, when the Israeli citizen communicates with someone from a western culture?
Due to the modern technology of today’s world, interaction between people from different socio-cultural groups is very high. This means that more and more often people get confronted with situations like the one above, where they cannot afford to assume but they need to demonstrate knowledge about socio-cultural matters, such as the socio-cultural time.
The situation is identical within the context of the World Wide Web. Web is a dynamic system, where the concept of time is necessarily present and where billions of people interact with each other. Besides, everyday various software and application systems are being built for the Web. These application systems are developed on the basis of the context-specific needs and preferences of their developers and the intended users. As a result, the application systems carry the characteristics of their socio-cultural contexts, which differ in nature. Hence, when the application systems interact, problems of inter-operability occur. Same applies to the handling of temporal information in Web application systems. As seen, it is also determined by socio-cultural characteristics analogous to the case in the real world. Hence, inter-operability problems related to the representation of temporal information occur.
The problem of different modelling of same domains due to different understandings and perceptions and its consequent undesirable outcomes have been recognized by the Web community. Different Web applications concerning the same domain, say the domain of time, cannot cooperate because their temporal information is encoded using different terminology, languages and components that reflect their developers’ conception of time. As we have seen, the conception usually depends on the socio-cultural context of the developers and of the intended users of the application. Ontology, which has wandered from the field of philosophy to the fields of AI and eventually to the fields related to the Web, is regarded in literature as the device to fight against the problem of clashing conceptions and terminologies [45],[46],[47],[49],[63],[66],[67],[68]. The idea behind is to define and advertise, in a formal and machine processable way, what an application system knows and how it conceives of one domain. On the basis of this information, application systems can be modified to become compatible with each other. Likewise, information about one domain can be defined by an ontology and it can be declared as the only way the information about the domain ought to look like. In other words it can be declared as the so-called normative model of the domain. Application systems that commit to this ontology automatically become inter-operable.
1.1 Motivation
Drawing upon the assumption of the existence of the socio-cultural time conception and of the consequent inter-operability problems within the context of the Web, we defend the idea that socio-cultural temporal information needs to be described for Web based temporal application systems. Yet, there are some requirements for such a description. It has to be formal, explicit, systematic and machine processable. Furthermore, it needs to be accessible to Web applications, so that diverse applications can commit to and share the same information. Clearly, ontologies fulfil all these requirements; therefore we have used the ontology as a device to describe machine processable knowledge about the domain of socio-cultural time for the Web.
During our research we have come across to numerous independent domain ontologies of time for the Web, e.g. [13],[39]. Culture ontologies cover the associated domain in its broadest sense, in that they provide models of cultural heritage systems [48],[21],[17],[78], of cultures in different enterprises and organisations [6], and of culture-specific language terms [7]. In doing so, these ontologies model the domain of culture and the domain of time as independent of each other. As we shall see, they do not touch the notion of socio-cultural time. Additionally, we have not come across to any ontology of socio-cultural time that formally describes the socio-cultural conception of time.
Information about the conception of socio-cultural time can be captured by inspecting the expressions of socio-cultural time. In other words, it is possible to gain insight to the time conceptions of a culture or a social group by observing how their members talk about time. We will show the ways to represent this information by means of ontology.
Once information about socio-cultural time is formalized in a machine processable way, it can be used to support temporal Web application systems such as a Web based automated appointment scheduling service. We believe appointment scheduling is a task, where different conceptions of time can be frequently observed, when parties involved in appointment scheduling process come from different socio-cultural backgrounds. In [79] the characteristics of such a Web based automated appointment scheduling service is defined and it is stated that current Web based appointment scheduling services fall short in considering the notion of socio-cultural time. Being supported with this kind of temporal information, such services can react in a more sensitive way to their users’ socio-cultural context dependent temporal needs and preferences. Additionally, on the basis of the socio-cultural temporal information defined in the ontology, socio-cultural calendars can be developed for individual use or as a component of a Web based automated appointment scheduling service. Clearly, this information can also be used for the semantic annotation of Web pages
1.2 Overview of the Thesis
The impetus of this thesis is twofold. First objective is to provide a brief introduction to the ontological engineering, which refers to the group of activities that involve the process of ontology development. Second objective is to present two ontologies we have developed that describe machine processable information about the domain of socio-cultural time related to nations, religions, business life & education.
Chapter 2 discusses the understanding of ontology in both disciplines of philosophy and computer science and it aims at a terminological clarification. The reasons why ontologies are necessary are discussed and some ontology kinds are introduced. Ontology development methodologies are mentioned, whereby one methodology, the METHONTOLOGY [3] comprises the focus. This methodology has also been used to develop the two ontologies in this thesis. Later, some well-known ontology languages such as the latest Web standard OWL [42] are briefly represented and some ontology development environments are mentioned. Finally, the application areas of ontologies such as natural language processing, multiagent architectures and the vision of Semantic Web are referred to and three current ontologies are introduced. Chapter 2 concludes with the discussion of the provided information.
Chapter 3 provides an overview of the ontological models that exist in the domain of time and in the domain of culture within the context of the Web. As we have stated previously, we have not come across to domain ontologies about socio-cultural time, therefore we have turned our attention to ontologies about the separate domains of time and culture. The main intention of this chapter is to exhibit how the current ontologies of time and ontologies of culture address the socio-cultural conception of time.
Chapter 4 reports on the status of ontologies in the field of Natural Language Processing (NLP). We can acquire knowledge about the socio-cultural time by studying the natural language expressions that denote the concepts of socio-cultural time. To put it simply, we can learn about the socio-cultural context dependent conception of time by looking at the ways how people from different cultures and societies talk about time. Since we want to investigate the socio-cultural time expressions that comprise a subset of natural language expressions, we enter the field of NLP. Moreover, we want provide an ontological model of such expressions, therefore in Chapter 4 we discuss the views of NLP about modelling natural language expressions by means of ontologies.
Chapter 5, which comprises the core of the thesis, is devoted to describing the two machine processable ontologies we have developed to model socio-cultural temporal information for the Web. These ontologies are the Ontology of Socio-Cultural Time Expressions Related to Nations, Religions, Business Life & Education (henceforth Ontology of Socio-Cultural Time Expressions) and the Ontology of Socio-Cultural Time Concepts Related to Nations, Religions, Business Life & Education (henceforth Ontology of Socio-Cultural Time Concepts) As such, the former ontology provides a lexical model of the domain, whereas the latter a conceptual model. The two models are to be understood as complementary to each other. The details of this approach will be discussed in detail throughout the chapter. Subsequently, Chapter 5 clarifies the role of the Ontology of Socio-Cultural Time Expressions providing an overview of the syntactic and semantic structure of the ontology. As next, the development process of the Ontology of Socio-Cultural Time Concepts is described step by step w.r.t. the ontology development methodology METHONTOLOGY. Likewise, the syntactic and the semantic structure of the ontology is discussed. Chapter 5 concludes with the presentation of two concrete applications that use the ontology to provide socio-cultural temporal support for existing temporal Web applications. Furthermore, a use case, which describes a possible future application of the ontology is explained.We conclude our thesis in Chapter 6 by presenting the results of the thesis and by referring to the future work that necessarily arises from the obtained results.
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