With the huge amount of information on the Internet, search has become increasingly important in travelers' use of the Internet for travel planning. However, developing useful search technologies to support travel planning requires substantial knowledge about the underlying world a technology represents, i.e., the online tourism domain. Arguably, online search engines provide the means for travelers to access to the tourism domain in a comprehensive way. As such, the goal of this dissertation is to assess the online tourism domain within the context of travelers' use of search engines for travel planning.

This dissertation primarily consists of two parts: first, the online tourism domain is conceptualized based upon theoretical perspectives in tourism literature with the emphasis on: tourism industry as a conglomeration of business entities; the symbolic representation of the industry in the form of "language of tourism"; and, the hierarchical, multi-faceted nature of information search for trip planning in the online environment. These literature streams provide directions for understanding the composition, form, and structural properties of the online tourism domain.

Second, guided by this conceptualization, a series of empirical studies were conducted to examine the online tourism domain, focusing on: (1) the extent to which the domain is represented through search engines; (2) the representational vocabulary of the domain, i.e., the ontology, represented on tourism related Web pages as well as user queries in search engines; and, (3) the language representation of the domain, i.e., words and their semantic relationships, in tourism related Web pages and user queries.

Results of this research show that the online tourism domain is semantically rich and current search technologies can only provide a limited representation. The tourism domain manifests characteristics that reflect the complexity and idiosyncrasies of destinations as well as the promotional purposes of the industry. This research also shows that there is a substantial gap between the language representations in tourism related Web pages and user queries. Based on the empirical analysis, the concept of the online tourism domain is defined using a series of propositions. In addition, implications for designing semantically driven search technologies to support travel planning are discussed.