Learning Semantic Web from E-Tourism Dr. Waralak V. Siricharoen Computer Science Department, School of Science, University of the Thai Chamber of Commerce, 126/1 Dindeang, Bangkok, Thailand
[email protected],
[email protected]
Abstract. Inquiring an information system in natural language is engaging in the special tourism domain because users usually have very different backgrounds regarding their computer literacy. The constant fast growth in travel related information measure makes it increasingly difficult to find, organize, access and maintain the information required by consumers (users). The Semantic Web provides enhanced information access based on the exploitation of machine-processable meta-data.E-tourism is a perfect candidate for Semantic Web because it is information-based and depends on the World Wide Web, both as a means of marketing and transaction channel. E-tourism/e-travel software adapted from original e-commerce, ready for creating instantly online reservation/booking. The Semantic Web relies heavily on the formal ontologies that structure underlying data for the purpose of comprehensive and transportable machine understanding. Therefore, the success of the Semantic Web depends strongly on the proliferation of ontologies. Ontologies can assist organization, browsing, parametric search, and in general, more intelligent access to online information and services. The ideas proposed in this paper, are particularly interested in the new possibilities afforded by Semantic Web technology in the area of knowledge management practical to the travel industry. This paper also discusses some ontological trends that support the growing domain of online tourism. The preview of e-tourism is introduced in general. The paper also gives the example concepts of existing e-tourism using ontologies display in graphical model presented in ontologies editor tool called Protégé and show the example of e-tourism ontologies description in OWL and RDFS syntax. The last part of the paper is a summary on the e-tourism ontologies projects. Keywords: Ontologies, E-commerce, E-tourism, Semantic Web, Travel, Tourism.
1 Introduction Tourism is an information based business. Tourists have to leave their daily environment for consuming the product. At the beginning of the 21st century, the structure of demand and supply in the tourism industry is undergoing significant changes. Social and economic changes, for instance age profile, life styles and organization of work, together with the fast distribution of the Internet, increasing e-business and the availability of online public services have had a strong impact on the demand for tourism N.T. Nguyen (Eds.): KES-AMSTA 2008, LNAI 4953, pp. 516–525, 2008. © Springer-Verlag Berlin Heidelberg 2008
Learning Semantic Web from E-tourism
517
products and their modes of provision [1]. The competitiveness and success of the tourism industry depend on the impact of social, economic and technological changes within society as a whole. Key among these global trends is the increase in the use of electronic services [2]. Today, tourism service suppliers are a group of many different users, most of them offering electronic services. Tourism has become the world's largest trade and its expansion shows a constant year-to-year raise. Kim addresses in the paper [3] that “Competitive benefit is no longer ordinary, but increasingly driven by science, information technology and innovation. The Internet is already the major source of tourist destination information for travelers”. This is support that the tourism business mission is to revolutionaries the traditional tourism industry to next generation e-tourism powered by Semantic Web technology. It will be realized by an advanced e-tourism Semantic Web portal which will connect the customers and virtual travel agents from anywhere at anytime with any needs and requests [4]. Tourism Information Systems are a new form of business systems that provide and support e-tourism and e-travel organizations, such as airlines, hoteliers, car rental companies, leisure suppliers, and travel agencies. One class of these systems relies on travel related information sources, such as Web sites, to create tourism products and services. ICTs enable tourism businesses to make tourism products and services directly available to a large number of consumers, and to interact with them as well as with other tourism producers and distributors [5]. Semantic Web will bring the revolution to this area by not only exponentially extending the dissemination and exchange channels with unlimited access, unlimited time and unlimited locations, but also assisting users with smart information searching, integrating, recommending and various intelligent services[6]. The Semantic Web will also be crucial to the development of Web applications such as e-commerce, providing users with much more sophisticated searching and browsing capabilities as well as support from intelligent agents such as shopbots (shopping "robots" that access vendor Web sites, compare prices etc.). Examples of the use of ontologies/taxonomies to support searching and browsing can already be seen at e.g., Yahoo Shopping and Amazon.com. Therefore, e-tourism is the one of the decent application areas for Semantic Web technologies and it is also a good test-bed to prove the efficiency and utility of Semantic Web technologies [7]. The e-tourism ontology provides a way of viewing the world of tourism. It organizes tourism related information and concepts. The ontology will allow achieving interoperability through the use of a shared vocabulary and meanings for terms with respect to other terms [8].
2 Semantic Web and E-Tourism Overall, e-tourism comprises electronic services, which include three basic service categories: Information services (e.g. destination and hotel information); Communication services (e.g. email, discussion); Transaction services (e.g. reservation and booking, payment). These services are typically offered via the Internet and are accessible from a variety of locations, from private PCs at home or at work to electronic kiosks and other devices in public places. The World Wide Web (WWW) as known it today is a huge collection of information or information superhighway. The number of websites on the WWW is growing daily. However, this expands of information is not as
518
W.V. Siricharoen
good as to an increase of functionality: information extraction has become a difficult task. Current technologies do not provide means to reuse existing information efficiently. Common search engines can perform keyword-based searches. Finding a certain part of information is very difficult. However, the number of results usually is enormous and not manageable by the human reader. For the human user it is simply impossible to go through all the websites that are delivered as results to a query. Objective of the Semantic Web is to make the information on the Web understandable and useful to computer applications in addition to humans. The Semantic Web promises a solution to this problem: Semantically annotated websites can not only be understood by the human reader but also by machines. Enriching websites with machine-readable semantics will enable more intelligent and efficient searching and further processing of data without requiring the human user to interfere [9]. Ontologies define data models in terms of classes, subclasses, and properties. For instance, we might define a carnivore to be a subclass of animals. In Fig. 1. shows very simple example ontology for animals [10].
Fig. 1. Example of animal ontology [10]
The challenge to develop software package [9] for online commerce is to find a solution to cope and integrate the non-standard way of defining e-tourism products and services. There are no standards or common criteria to express transportation vehicles, leisure activities, and weather conditions when planning for a vacation package, several ways can be found among all the existing Web sites. The information from several travel, leisure, and transportation online sites, it point out the lack of standards in the tourism domain. Some of the differences founded among several sites are the following example. The price of tourism related activities and services are expressed in many different currencies (Thai baht, euros, dollars, British pounds, etc.). To finding a solution to improve on this lack of standards in the tourism field by automatically understanding the different ways of expressing tourism products and services, extracting its relevant information and structuring. The sophisticated technologies, such as semantics and ontologies, are good candidates to enable the development of dynamic information systems [11]. Ontology can be constructed for e-tourism. Tourism is a data rich domain. Data is stored in many hundreds of data sources and many of these sources need to be used in concert during the development of tourism information systems. The e-tourism ontology provides a way of viewing the world of tourism. It organizes tourism related information and concepts. The e-tourism ontology provides
Learning Semantic Web from E-tourism
519
a way to achieve integration and interoperability through the use of a shared vocabulary and meanings for terms with respect to other terms. The e-tourism ontology was developed using OWL (Web Ontology Language). OWL was proposed by the W3C for publishing and sharing data, and automating data understanding by computers using ontologies on the Web [6]. Ontology is mentioned by Tom Gruber which used to refer to “an explicit specification of a conceptualization [of a domain]. In other words, ontology refers to a formalization of the knowledge in the domain. Ontology is the concept which is separately identified by domain users, and used in a selfcontained way to communicate information. Combination of concept is the knowledge base or knowledge network. Some of the reasons why someone want to develop an ontology are to share common understanding of the structure of information among people or software agents, to enable reuse of domain knowledge, to make domain assumptions explicit, to separate domain knowledge from the operational knowledge, to analyze domain knowledge [12]. An ontology structure holds definitions of concepts, binary relationship between concepts and attributes. Relationships may be symmetric, transitive and have an inverse. A minimum and maximum cardinality constraint for relations and attributes may be specifies. Concepts and relationships can be arranged in two distinct generalization hierarchies [13]. Concepts, relationship types and attribute abstract from concrete objects or value and thus describe the schema (the ontology) on the other hand concrete objects populate the concepts, concrete values instantiate the attributes of these objects and concrete relationship instantiate relationships. Three types of relationship that may be used between classes: generalization, association, and aggregation [5].
Season: When
Ontolo-
Place: Where
Transportation:How
Activities: What
Fig. 2. The e-tourism ontologies explanation
520
W.V. Siricharoen
Ontology is able to answers four types of questions that can be asked when developing the e-tourism package. These questions involve the predicates What, Where, When, and How. Examples of typical questions are in Fig. 2. [4]: What can a tourist do while staying?, Where are located the interesting places to see and visit, When can the tourist visit a particular place? , How can the tourist get to its destination to see or do an activity?. Classes are the focus of most ontologies [12]. A class can have subclasses that represent concepts that are more specific than the superclass. Slots describe properties of classes and instances. Ontologies for the Semantic Web are characterized as Resource Description Framework (RDF) ontologies, and are being built using OWL and other languages based on RDF. This ontology growth in direct support for RDF and various species of OWL has created some controversy [14]. Shared ontologies allow for different systems to come to a common understanding of the semantics of learning concepts. The present the required ontology model including the formal expression of ontology, mapping to Extensible Markup Language (XML) representation and the corresponding system architecture for binding web services. Two important technologies for developing the Semantic Web are XML and RDF. XML is accepted as a standard for data interchange on the Web. It is a language for semi-structured data. RDF uses XML and it is at the base of the semantic Web. It is a metadata language for representing information in the Web and provides a model for describing and creating relationships between resources. Resource Description Framework Schema (RDFS) is technologically advanced compared to RDF. RDFS allows users to define resources with classes, properties, and values. A class is a structure of similar things and inheritance is allowed. RDFS property can be viewed as an attribute of a class. RDFS properties may inherit from other properties, and domain and range constraints can be applied to focus their use. In OWL an ontology is a set of: Classes, Properties, Constraints on the classes and properties. OWL adds a layer of expressive power to RDFS. Uses formal logic to describe the semantics of classes and properties. Build on top of RDF and RDFS. Over the years a vast amount of research has been carried on how to represent and reason about knowledge. In Europe funding has been heavily concentrated on the development of OIL (Ontology Inference Layer), a language for defining ontologies. In the US, DARPA funded a somewhat similar project called DAML (Distributed Agent Markup Language). More recently these activities have been combined into a project to work on a merged ontology language, DAML+OIL. In late 2001 the W3C set up a working group called WebOnt to define an ontology language for the Web, based on DAML+OIL. All of these ontology languages aim to provide developers with a way to formally define a shared conceptualization of a domain. They encompass both a means of representing the domain and a means of reasoning about that representation, typically by means of a formal logic. In the case of DAML+OIL this is Description Logic [10]. Jakkilinki [15] provide an overview of the development methodology and applications for tourism ontologies. Ontologies are created using ontology development tools, such as Protégé [16]. A Java-based ontology editor with OWL Plugin: that means that it allows ontology implementation as an applet on the Web. This permits multiple users to share the ontology. The W3C has recently finalized the OWL as the standard format in which ontologies are represented
Learning Semantic Web from E-tourism
521
online. With OWL it is possible to implement a semantic description of the travel domain by specifying its concepts and the relationships between the concepts. Usually, there is several tourism ontologies were considered for reuse, before considering built the new ontology. In e-tourism different ontologies have been developed for different areas. However, sometimes in different countries or regions around the world, the existing ontologies might not meets the needs to describe regional distinctions for any specific areas. An international standard is the thesaurus on Tourism & Leisure Activities of the World Tourism Organization (WTO). It is a very extensive collection of terms related to the area of tourism. The example of e-tourism ontology developed by DERI [17], the project started with a list of terms that should be included in the ontology. On the one hand it was helpful to have a voluminous collection of terms, and on the other hand it was misleading because the broad range of terms sometimes led to too detailed concepts, which had to be taken out in a later stage of the development [17]. Ontologies enhance the semantics by providing richer relationships between the terms of a vocabulary. Ontologies can serve as point of reference to map against. The intelligent agents and more to come each day could then make suggestions on consumers; make arrangements in consideration of consumer preferences. For these agents, the Semantic Web infrastructure would be based on core travel ontologies that would be published on fixed URI’s (Universal Resource Indicators) as OWL files. Ontologies would allow these providers to publish metadata about their travel services and contact information. The following code is showing the example of two different etourism ontologies presented in the same Ontology Editor Program called Protégé [16]. And also below shows example of OWL ontologies description in e-tourism ontology. It show that there are classes Accommodations, Guestroom, etc. which the Accommodations classes have object property called hasRoom. These classes and properties are quite normal for tourism/travel domain.
